Your roof is probably several shapes. What matters is the lines where they meet.
Steep-slope · single-family · mixed shapes
A combination roof is a set of ordinary shapes joined by a set of junctions. The shapes are easy. The junctions are where the flashing, the labour, and the leaks are.
What is a combination roof, and how do I work out what mine is?
A combination roof is two or more roof shapes on one building. Most houses that are not a plain rectangle have one. The shapes themselves are ordinary; the value is in the transitions where they meet. Each junction is a valley, a headwall, a sidewall, or a pocket with nowhere to drain, and each is a flashing detail rather than field roofing.
The short versionSection link
What a combination roof is, how ordinary it is, and what the page will and will not give you.
- What it is
- Two or more roof shapes on one structureGable plus hip, gable plus shed, hip plus a flat porch. There is no separate “combination” shape — the name describes the assembly, not a form.
- How ordinary it is
- 72% and 63% of houses had complex roofs, in the two US counties one study classified from satellite imageryNew Hanover County, North Carolina and Miami-Dade County, Florida. “Complex” there means the study’s own category — a cross-gable or cross-hip roof — so it counts a subset of what this page calls a combination and is a floor rather than a total. Both counties are coastal and hurricane-prone, neither is a national sample, and 17% and 11% of houses could not be classified at all.
- What you are actually counting
- Planes, and the lines where planes stopNearly every plane edge is an eave, a rake, a ridge, a hip, a valley or a wall — plus the break line where one run changes slope into another. Only the valley, the wall and the break are places where water has to be carried across a joint.
- Where the risk concentrates
- Valleys and roof-to-wall junctionsDOE’s Building America guidance calls valleys and penetrations “among the most vulnerable areas for water intrusion.”
- The limit a tie-in can quietly break
- 2:12 minimum slope for asphalt shinglesBuilding America: shingles “should only be installed on roof slopes of 2 in 12 or greater,” and from 2:12 up to 4:12 “a double underlayment application is required.” Guidance, not the law where you live — confirm against your adopted code.
- The unit that prices a transition
- Lineal feet and details, not squaresThis page publishes no dollar figure. The complexity multiplier is worked through on the complex geometry page instead of being asserted twice.
This page says inventory your transitions before you take a single price. Here is when that is the wrong move.Section link
The position taken here is that a homeowner who can name the junctions on their own roof gets a better proposal and a better repair. That position has real limits, and some of them are about what a ground-level survey genuinely cannot see.
Best when
- You are about to collect quotes and the proposals you have seen so far are a single price per square with no line items under it.
- The house has visibly been added to — a wing, an attached garage, a rear extension, an enclosed porch. A roof tied in later is where the detailing changes and where the two eras of construction meet.
- There is a leak whose location has never made sense. Junctions are the parts DOE’s Building America guidance calls the most vulnerable areas for water intrusion, and water rarely surfaces directly below where it got in.
- You are buying and want to know what you are inheriting before an inspection report lands, so you can ask the inspector about specific junctions rather than about the roof in general.
- There is more than one covering on the roof, or more than one age of covering. That is usually a map of the building’s history and of who detailed each boundary.
- You can get an overhead image and walk the perimeter at ground level. That is the entire method; nothing else is required.
Think twice if
- Water is coming in now. Stop inventorying and get the intrusion stopped — the first hours and the stop-and-call-a-professional line are on the emergency tarping page.
- The building is low-slope throughout. Then this page’s vocabulary of ridges and valleys is the wrong frame, and drains, scuppers, crickets and positive slope to drain are the right one.
- You are tempted to climb, to open the attic, or to lift a shingle to check a detail. An inventory is not worth that, and the details that matter most are under the covering anyway.
- You want a price. This page deliberately publishes none. Roof shape moves a price through complexity, waste, and production speed, and no transparent national dataset isolates the shape from the covering and the market.
- You expect the inventory to replace an inspection. It is a list of questions, not a condition assessment. A transition can be perfectly detailed and invisible from the ground, or badly detailed and equally invisible.
- The house predates 1990 and the work would disturb old felts, mastics, or cement-based products. EPA is plain that “the only way to be sure whether a material contains asbestos is to have it tested by a qualified laboratory,” and it advises testing before a renovation that would disturb suspect material.
What changes the answer
- Whether the shapes were built together or tied in years apart. A junction built by two different crews in two different decades is a different risk from one framed in a single day.
- The slope of each plane, which decides what covering is permitted on it and whether two planes can share one specification.
- Which way each junction faces. A north-facing valley in a cold climate holds snow and ice long after a south-facing one has cleared.
- Whether there is a gutter, and a working downspout, under each point where a large plane discharges onto a small one.
- What the wall cladding is at each sidewall. Building America notes that “new wall claddings like fiber cement, vinyl siding, and brick veneer can mask the evidence for years.”
- Whether you are re-roofing or repairing. A re-roof is the moment when flashings are accessible and replaceable; a repair usually is not.
- What your jurisdiction has adopted and amended, and what its authority having jurisdiction will require on the permit.
A roof is planes. The money and the leaks are on the lines where planes stop.Section link
Four ordinary shapes on one ordinary house. Read the letters first — those are the shapes, and they are the easy part. Then read the numbers, which are the junctions between them.
The shapes
- A — the main side gable. Two planes, one ridge, two eaves, two rakes. On its own this is the simplest roof in American house building — see the gable page. Standing alone it would have no junctions at all; everything numbered below is something the other three shapes did to it.
- B — a cross gable wing toward the street. Another gable, narrower than the main house and set at right angles to it. Because it is narrower and its eaves sit at the same height, its ridge cannot reach the main ridge: it stops partway up the main slope, at the small open circle in the drawing.
- C — a hipped garage wing. A hip roof: a short ridge with two hips running out to the far corners, eaves on three sides, and no gable end. See the hip page for why that shape behaves differently in wind and costs more to frame.
- D — a shed addition across the back. One shed plane sloping away from the house, usually shallower than whatever it is attached to, and very often built later than the house it is attached to. See the shed page.
The transitions
- Two valleys, meeting at one point. Where wing B runs into the main roof it makes a pair of valleys. A valley takes the runoff of two planes and routes it through one line, which is why it is detailed differently from the field. Both valleys terminate at the same upslope point, where B’s ridge dies into A’s slope. NRCA names exactly that condition — the upslope end “(ridge, dormer crest and unequal rafter lengths)” — as one of the key points in every valley detail.
- A sidewall. The garage roof runs up alongside the main house’s end wall, so the wall runs with the slope. That is a sidewall, and it is flashed one piece per shingle course — step flashing — not with a single continuous strip. Building America gives the dimensions it cites from the model code: extend it “at least 4 inches up the wall from the roof deck and at least four inches out along the roof deck.”
- Kickouts, at the bottom of each sidewall run. Where the sidewall reaches the eave, everything that ran down that junction arrives at once. A kickout turns it into the gutter. Building America’s instruction is to “install kick-out flashing at the end of a roof-wall intersection to divert water away from the wall and into gutters.” There are two of them on this roof and two more at the dormer, and all four are the size of a hand.
- A ridge meeting a wall. The garage ridge stops dead against the main house wall rather than against another roof plane. Two planes and a wall converge on one point, and the waterproofing has to close all three there.
- The addition tie-in. Shed D’s high edge meets the back wall of the house as a headwall, flashed with a continuous apron rather than steps because the wall runs across the slope. Directly above that joint, the whole upper slope of A discharges over its eave. Building America’s guide for existing homes treats this family of details together: “transitions to those assemblies such as lower roofs, porch roofs, decks, balconies, railings, and dormers.”
- The shed dormer. A dormer is not one junction, it is five separate details: a cheek down each side flashed as a sidewall, a kickout at the bottom of each of those two cheeks, and a headwall across the top. Building America also treats it as a structural item, noting that dormers “can add significant additional uplift and torsional loads to the main roof and the rest of the house.”
- The chimney and its cricket. An apron below, steps up both sides, and counterflashing that Building America describes as “embedded into the mortar joints of the brick layer” and overlapping the base and step flashing. On the upslope face, a cricket: “a cricket or saddle flashing should be installed to redirect rainwater that is draining down the roof slope around the chimney.”
The six kinds of line on this roof, and why only two are hard
Every edge of every roof plane on this house is one of six things, and the legend on the drawing names all six. Three of them are places water leaves or divides: an eave is where it runs off, a rake is where it runs off sideways, and a ridge is where two planes turn their backs on each other. A hip is a fourth: two planes meeting and shedding away from the line. None of those four asks the waterproofing to carry a concentration of water across a joint.
The remaining two do. A valley combines two planes’ runoff into one line and accelerates it. A roof-to-wall junction stops the roof against something that is not a roof, and asks two different water-management systems — the roof and the wall — to be lapped together in the right order. That is the entire distinction this page is built on, and it is why a house with three shapes is not simply a house with more roof.
One line the legend does not carry, because this house does not have one, is the break where a single run changes slope into another — a gambrel, a mansard, or a shallower continuation of a steeper plane. It behaves like the second of the two hard ones: the covering stops and a flashed detail carries the water across. It is in the catalogue below for that reason.
The rest of the plane — the field — is the part a covering is genuinely good at. The junctions are where the covering stops and flashing takes over. IBHS puts the flashing’s job plainly: “the primary function of roof flashing is to shed or direct water away from roof edges and penetrations to prevent infiltration into the building.”
“Most houses are a combination of shapes” is true, and almost nobody has actually countedSection link
It is worth being precise about what is measured and what is asserted, because this page rests on the claim and the claim rests on two counties.
There is no federal inventory of residential roof shapes. The authors of a recent attempt to build one state the problem directly: roof type is “the most frequently missing building feature from publicly available databases.” Nobody collects it, so nobody can total it nationally.
What exists is measurement at county scale. A team at UCLA trained an image classifier on satellite imagery and applied it to 161,772 single-family houses in New Hanover County, North Carolina and Miami-Dade County, Florida. Their finding on complexity is the single most useful number for this page: “Regarding roof complexity, 72% and 63% of houses have complex roofs (i.e., simple cross-gable, complex cross-gable, and cross-hip) in New Hanover County and Miami-Dade County, respectively.”
Three qualifications, all of which matter and none of which cancel the finding. First, both counties are coastal and hurricane-prone; neither stands in for the United States. Second, the classifier could not assign a type at all for 17 percent of houses in New Hanover and 11 percent in Miami-Dade. Third — and this is the one most relevant here — the paper’s five categories are all gable-family or hip-family shapes. A house whose complication is a shed addition, a porch roof, or a flat section over a rear extension is not counted as complex by that taxonomy at all. The measured share is therefore a floor, not a ceiling, for the thing this page is about, and it is presented here as evidence rather than as a national figure.
The gable page draws on the same study for a different question — how dominant the gable shape is — and prints these same complexity figures in a table there, so the two pages are quoting one small study rather than two independent measurements. It is still the best available answer to a question that is usually asserted without one.
How to read your own roof from the ground, in six stepsSection link
Nothing here requires a ladder, a drone, or a contractor. It requires a walk around the building, a phone camera, and an overhead image.
The goal is not to diagnose anything. It is to produce a written inventory: a list of the shapes, and a list of the junctions between them. That list is what turns a vague conversation about “the roof” into a specific one about named places.
Step 1 — get an overhead image
Any mapping service will give you a satellite or aerial view of your address, and that view is a roof plan: exactly the drawing above. Machine classifiers assign roof types from precisely this imagery, so the shapes are genuinely legible in it. Print it, or screenshot it, and draw on it. If the imagery predates an addition, that discrepancy is itself information.
Step 2 — walk the perimeter and mark every eave and rake
Stand at each corner of the building and look up. An eave is a low edge with a gutter, or where a gutter would go. A rake is a sloping edge running up to a peak. Mark each one on your printout. When the outline is closed, you have the footprint of the roof.
Step 3 — count ridges
Each horizontal peak line is a ridge. Count them from two opposite corners of the property, because one ridge frequently hides behind another. Roughly speaking, each ridge belongs to one shape, and the number of ridges is your first estimate of how many shapes you are dealing with.
Step 4 — find every place a roof meets a wall
This is the step most people skip and the one that matters most. Look for any roof plane that ends against a wall instead of at open air. The three common cases:
- A sidewall — the wall runs up the slope alongside the roof. Typical at an attached garage, a two-storey section beside a single-storey one, and at both cheeks of every dormer. Flashed course by course.
- A headwall — the wall runs across the slope, so the whole width of the plane above arrives at the joint. Typical where an addition or a porch roof stops against the main house. Flashed with a continuous apron.
- A chimney, skylight, or curb — a wall on all four sides at once, which needs an apron below, steps up the sides, and something to split the water above.
At the bottom of every sidewall run, look specifically for a small metal diverter turning water into the gutter. If you cannot see one, write it down as a question rather than as a fault — it may be hidden behind the gutter, and it may genuinely not be there.
Step 5 — find the valleys
A valley reads from the ground as a diagonal line where two planes fall toward each other. Two reliable tells: debris and a darker weathering streak collect along it, and there is very often a downspout directly below where it lands. Note also what each valley runs into at the top — a ridge, a dormer, or nothing obvious.
Step 6 — note every change of slope
Photograph the house square-on from across the street. Slopes that look identical from an angle separate immediately in a flat elevation. Where two planes are visibly different angles, they may not be able to carry the same covering — which is a scope question, not an aesthetic one. If you want the numbers behind that, the pitch page has the arithmetic.
What this method genuinely cannot see
Be honest with yourself about the boundary, because the value of the inventory depends on it. From the ground you cannot tell whether step flashing was lapped under the wall’s drainage plane or laid over it; whether there is underlayment in the valley or bare deck; whether a kickout exists behind the gutter; whether the flashing at a junction is new or thirty years old; or what the deck under any of it is doing. Every one of those is a question your inventory produces and a contractor or inspector answers. The list is the deliverable. Nothing on it is a diagnosis.
Eleven transitions, what each looks like from the ground, and how each failsSection link
This is the reference half of the page. Find the rows that match your inventory and ignore the rest.
| Transition | How to spot it from the ground | What has to be right there | How it fails |
|---|---|---|---|
| Valley | A diagonal line where two planes fall toward each other, usually holding debris and showing a darker weathering streak. Often a downspout directly below it. | Underlayment carried the full length of the valley, and a valley method chosen for this covering and this slope. NRCA recommends a full-width polymer-modified bitumen sheet under it. | Debris packs the line and holds water against it. In cold climates it holds ice: Building America notes valleys are difficult to ventilate and so more prone to heat accumulation and snow melt. |
| Hip | A diagonal line where two planes meet and shed away from each other — the outline has no gable triangle at that end. | Cut waste, hip and ridge cap, and closure. The covering is cut on both sides and capped over the line, but both planes shed away from it, so no water is carried across that joint. | Rarely a leak point. It is a labour and waste point, and face-nailed cap lifts in wind. |
| Sidewall (wall running with the slope) | A roof plane dying into a taller wall — an attached garage, a two-storey section beside a lower one. Look for cladding that stops in a stair-step just above the shingles. | Step flashing, one piece per course, integrated with the wall’s drainage plane. Building America: extend it “at least 4 inches up the wall from the roof deck and at least four inches out along the roof deck.” | A single continuous strip instead of steps; flashing lapped over the housewrap instead of under it; old flashing reused at a re-roof. |
| Kickout (bottom of a sidewall) | Stand where a roof edge meets a wall above a gutter and look at that corner. Either there is a small diverter or there is not. | Building America: “install kick-out flashing at the end of a roof-wall intersection to divert water away from the wall and into gutters.” | Omitted, and the damage is inside the wall. Building America: claddings “like fiber cement, vinyl siding, and brick veneer can mask the evidence for years.” |
| Headwall (wall running across the slope) | A roof plane that stops against a wall face-on, so the full width of the plane above arrives at one line. Typical at additions and porches. | Continuous apron flashing up the wall and out onto the roof, lapped by the wall’s drainage plane, and counterflashed where the wall is masonry. | Surface-sealed with mastic instead of let in or lapped; too short; and the wall above delivering its own water into the same joint. |
| Dormer | A window projecting out of a roof slope. Count it as at least five separate details, not one. | A cheek flashed as a sidewall on each side with a kickout at the bottom of each, a head condition at the top, and — on a gable dormer — two valleys where its roof dies into the main plane. | Building America on the structural side: dormers “can add significant additional uplift and torsional loads,” and “often there aren’t engineering specifications for the connection in this area.” |
| Addition or porch tied in below a main plane | A newer, lower wing whose roof is usually shallower than the main roof, sometimes with a different covering or a visibly different age of covering. | The addition’s high edge flashed as a headwall, its own drainage, and a covering appropriate to its own slope. Building America’s existing-homes guide covers exactly these “transitions … such as lower roofs, porch roofs, decks, balconies, railings, and dormers.” | The main roof discharging directly onto a small shallow plane with no gutter between them; and shingles carried across a slope below their range. |
| Change of slope within one run | A horizontal line across a plane where the roof visibly changes angle. Easiest to see in a square-on photograph from across the street. | A flashed break, and a check that each slope is within the covering’s range. Building America: shingles “should only be installed on roof slopes of 2 in 12 or greater”, with double underlayment from 2:12 to 4:12. | One underlayment specification written for both slopes, so the shallower run gets the steeper run’s assembly. |
| Ridge dying into a plane or a wall | A ridge that simply stops partway up another roof, or stops dead against a wall, instead of running to an end. | The upslope termination of two valleys at a single point, or a saddle where a ridge meets a wall. NRCA names the upslope end — “ridge, dormer crest and unequal rafter lengths” — as a key point in all valley details. | One piece of material asked to close three planes at a point; and the pocket immediately above it collecting debris and holding it against the joint. |
| Chimney | Masonry passing through a roof plane. Look at the upslope face specifically: is there a small triangular roof behind it, or does the roof run straight into the brick? | Apron below, steps up both sides, counterflashing “embedded into the mortar joints … overlapping the base flashing and the step flashing”, and a cricket above: Building America says one “should be installed to redirect rainwater that is draining down the roof slope around the chimney.” | Counterflashing surface-sealed to the brick face rather than let in. No cricket, so the upslope face collects water, snow and debris against a flashing joint. |
| Pocket with no fall (a dead valley) | A corner between two shapes that stays dark for a day after the rest of the roof has dried, and where leaves never clear. | Usually a low-slope assembly detailed as one, or a cricket built to give the water a direction. Not a shedding covering laid flatter. | Standing water on a lapped, water-shedding system; repeated sealant repairs to the same square metre. |
Read this table one item at a time
Valley
- How to spot it from the ground
- A diagonal line where two planes fall toward each other, usually holding debris and showing a darker weathering streak. Often a downspout directly below it.
- What has to be right there
- Underlayment carried the full length of the valley, and a valley method chosen for this covering and this slope. NRCA recommends a full-width polymer-modified bitumen sheet under it.
- How it fails
- Debris packs the line and holds water against it. In cold climates it holds ice: Building America notes valleys are difficult to ventilate and so more prone to heat accumulation and snow melt.
Hip
- How to spot it from the ground
- A diagonal line where two planes meet and shed away from each other — the outline has no gable triangle at that end.
- What has to be right there
- Cut waste, hip and ridge cap, and closure. The covering is cut on both sides and capped over the line, but both planes shed away from it, so no water is carried across that joint.
- How it fails
- Rarely a leak point. It is a labour and waste point, and face-nailed cap lifts in wind.
Sidewall (wall running with the slope)
- How to spot it from the ground
- A roof plane dying into a taller wall — an attached garage, a two-storey section beside a lower one. Look for cladding that stops in a stair-step just above the shingles.
- What has to be right there
- Step flashing, one piece per course, integrated with the wall’s drainage plane. Building America: extend it “at least 4 inches up the wall from the roof deck and at least four inches out along the roof deck.”
- How it fails
- A single continuous strip instead of steps; flashing lapped over the housewrap instead of under it; old flashing reused at a re-roof.
Kickout (bottom of a sidewall)
- How to spot it from the ground
- Stand where a roof edge meets a wall above a gutter and look at that corner. Either there is a small diverter or there is not.
- What has to be right there
- Building America: “install kick-out flashing at the end of a roof-wall intersection to divert water away from the wall and into gutters.”
- How it fails
- Omitted, and the damage is inside the wall. Building America: claddings “like fiber cement, vinyl siding, and brick veneer can mask the evidence for years.”
Headwall (wall running across the slope)
- How to spot it from the ground
- A roof plane that stops against a wall face-on, so the full width of the plane above arrives at one line. Typical at additions and porches.
- What has to be right there
- Continuous apron flashing up the wall and out onto the roof, lapped by the wall’s drainage plane, and counterflashed where the wall is masonry.
- How it fails
- Surface-sealed with mastic instead of let in or lapped; too short; and the wall above delivering its own water into the same joint.
Dormer
- How to spot it from the ground
- A window projecting out of a roof slope. Count it as at least five separate details, not one.
- What has to be right there
- A cheek flashed as a sidewall on each side with a kickout at the bottom of each, a head condition at the top, and — on a gable dormer — two valleys where its roof dies into the main plane.
- How it fails
- Building America on the structural side: dormers “can add significant additional uplift and torsional loads,” and “often there aren’t engineering specifications for the connection in this area.”
Addition or porch tied in below a main plane
- How to spot it from the ground
- A newer, lower wing whose roof is usually shallower than the main roof, sometimes with a different covering or a visibly different age of covering.
- What has to be right there
- The addition’s high edge flashed as a headwall, its own drainage, and a covering appropriate to its own slope. Building America’s existing-homes guide covers exactly these “transitions … such as lower roofs, porch roofs, decks, balconies, railings, and dormers.”
- How it fails
- The main roof discharging directly onto a small shallow plane with no gutter between them; and shingles carried across a slope below their range.
Change of slope within one run
- How to spot it from the ground
- A horizontal line across a plane where the roof visibly changes angle. Easiest to see in a square-on photograph from across the street.
- What has to be right there
- A flashed break, and a check that each slope is within the covering’s range. Building America: shingles “should only be installed on roof slopes of 2 in 12 or greater”, with double underlayment from 2:12 to 4:12.
- How it fails
- One underlayment specification written for both slopes, so the shallower run gets the steeper run’s assembly.
Ridge dying into a plane or a wall
- How to spot it from the ground
- A ridge that simply stops partway up another roof, or stops dead against a wall, instead of running to an end.
- What has to be right there
- The upslope termination of two valleys at a single point, or a saddle where a ridge meets a wall. NRCA names the upslope end — “ridge, dormer crest and unequal rafter lengths” — as a key point in all valley details.
- How it fails
- One piece of material asked to close three planes at a point; and the pocket immediately above it collecting debris and holding it against the joint.
Chimney
- How to spot it from the ground
- Masonry passing through a roof plane. Look at the upslope face specifically: is there a small triangular roof behind it, or does the roof run straight into the brick?
- What has to be right there
- Apron below, steps up both sides, counterflashing “embedded into the mortar joints … overlapping the base flashing and the step flashing”, and a cricket above: Building America says one “should be installed to redirect rainwater that is draining down the roof slope around the chimney.”
- How it fails
- Counterflashing surface-sealed to the brick face rather than let in. No cricket, so the upslope face collects water, snow and debris against a flashing joint.
Pocket with no fall (a dead valley)
- How to spot it from the ground
- A corner between two shapes that stays dark for a day after the rest of the roof has dried, and where leaves never clear.
- What has to be right there
- Usually a low-slope assembly detailed as one, or a cricket built to give the water a direction. Not a shedding covering laid flatter.
- How it fails
- Standing water on a lapped, water-shedding system; repeated sealant repairs to the same square metre.
Every row describes a condition, not your building. A transition can be detailed correctly and be invisible from the ground, or detailed badly and be equally invisible. Nothing in this table is a code requirement anywhere: the guidance quoted cites model provisions of the 2015 and 2018 IRC, and what binds you is the edition your jurisdiction adopted, as amended, as interpreted by its authority having jurisdiction.
What the inventory looks like when it is filled inSection link
The house in the diagram is unremarkable — a gable, a wing, a garage, a rear addition, one dormer, one chimney. Here is the count it produces.
Working through the plan above line by line gives a specific tally rather than an impression:
- 4 shapes — a side gable, a cross gable wing, a hip, and a shed.
- 9 roof planes — two on the main roof, two on the wing, three on the hipped garage, one on the addition, one on the dormer.
- 3 ridges, 2 hips, 2 valleys.
- 7 separate roof-to-wall runs — two step-flashed runs alongside the garage (the ridge splits the wall into two), an apron at the rear addition, two dormer cheeks, one dormer headwall, and the chimney.
- 4 kickouts — one at each end of the two garage sidewall runs, one at the bottom of each dormer cheek.
- 1 cricket, on the upslope side of the chimney.
- 2 points where a ridge dies into something that is not another roof plane — the wing ridge into the main slope, the garage ridge into the main wall.
Now the comparison that makes the point. Take the same quantity of roof area and put it on a plain rectangular house with a side gable. The tally reads: 2 planes, 1 ridge, 0 hips, 0 valleys, 0 roof-to-wall runs, 0 kickouts, 0 crickets, 0 ridge terminations. Not fewer — none. Every item on the first list is a place where the covering stops and someone has to make a joint; the second roof has no such place anywhere outside its penetrations.
That is why two roofs of similar area are not comparable on a price per square, and why “we will flash everything as needed” is not a scope of work. On this house the flashing scope alone is twelve named details — seven roof-to-wall runs, four kickouts and a cricket — before the two valleys are counted, and four of those twelve are the size of a hand. The arithmetic of what all of it does to a price — lineal feet of edge per square, and why two same-size roofs quote differently — is worked through on the complex geometry page, which is where it belongs. This page’s job ends with the list.
The addition tie-in, and the covering rule it can quietly breakSection link
This page’s judgement, offered as judgement and not as a statistic: if you only write down one transition, write down the place where something newer was joined to something older.
An addition is usually built to a head-height constraint rather than a roofing one. The result is often a plane shallower than the main roof, meeting the house at a headwall, directly beneath the point where the main roof discharges. The shed roof page works through how that head-height constraint sets the slope; the concern here is the junction it lands on. Three things can go wrong there, and they compound.
The slope. Building America states plainly that asphalt shingles “should only be installed on roof slopes of 2 in 12 or greater,” and that “for roof slopes from 2 in 12 up to 4 in 12, a double underlayment application is required.” An addition roof can easily land under 2:12 without anybody measuring, and the same shingles get carried across it because the covering matching is the visible priority. The correct answer at that point is a different system — a residential low-slope membrane detailed as one — not the same shingles laid flatter. What your jurisdiction requires is set by the edition it adopted; what the manufacturer permits is set by its published application instructions, which can be more restrictive than the guidance figure above.
The water arriving from above. The upper roof discharges over its eave onto a much smaller plane. If there is a gutter and a working downspout on the upper eave, that flow is intercepted. If there is not — something to check rather than assume — the addition’s covering, its headwall flashing, and eventually the wall behind it are taking the whole upper slope’s runoff at a concentrated point.
The joint itself. The addition’s high edge against the house wall is a headwall, and it has to be lapped into the wall’s water management, not sealed onto its face. Building America’s retrofit guide is written around exactly this family of conditions, covering “transitions to those assemblies such as lower roofs, porch roofs, decks, balconies, railings, and dormers” — and its framing principle is the one to hold on to: “shed water by layering materials in such a way that water is directed down, out, and away from the building.”
None of this makes an addition a bad idea. It makes the tie-in a named item. If you write one line on your inventory, write that one: the slope of the addition, whether there is a gutter above it, and what the flashing at its high edge is.
What to do with the inventory once you have itSection link
The point of counting is not to become an estimator. It is to make the junctions visible in a document, so that two proposals can be compared on something other than a headline number.
Take your marked-up overhead image to the site visit. Ask each contractor to walk it with you and annotate it. Three things happen, all of them useful.
- You find out who has counted. A contractor who names each junction and says what they intend to do at it has priced the roof you actually have. One who does not engage with the drawing has priced a rectangle.
- The proposals become comparable. Two prices for “the roof” are not comparable when one includes new step flashing at a sidewall and the kickouts under it and the other does not mention flashing at all. Normalising scope before comparing price is the whole method on the quote comparison page.
- You get an honest allowance. Junctions are where deck damage is found, because they are where water has been getting in. A proposal that carries a stated unit rate for deck repair is being straight with you about that; one that carries no rate at all will produce a number after the covering is off, when you have no leverage.
One caution to keep the page honest. A long list of junctions is not evidence that anything is wrong, and it is not a reason to accept an inflated price. Complexity is a real cost driver and it is also a convenient story for a padded bid. The defence against both is the same document: named details, priced individually, that a second contractor can be asked to price against.
What changes this on a real buildingSection link
Six things that change what a combination roof means on a specific building.
- Slope and drainage
Every plane sends its water somewhere, and on a combination roof that somewhere is frequently another plane or a wall rather than a gutter. The rear addition in the diagram receives the whole upper slope of the main house immediately above its headwall. A valley receives two planes at once. Work out, for each junction, how much roof is upstream of it — that is the number that decides whether the detail is trivial or the most loaded point on the building.
- Moisture and ventilation
Building America is direct: “valleys and penetrations through the roof decking are among the most vulnerable areas for water intrusion,” and recommends a self-sealing bituminous membrane or equivalent along all valleys, properly integrated into the adjoining roofing materials. It also notes a cold-climate effect that catches people out — because roof valleys are difficult to ventilate, they are more prone to heat accumulation and therefore to snow melt, which can contribute to ice dam formation and subsequent leakage.
Where an ice barrier is required, and how far up the slope it must run, depend on the code edition your jurisdiction adopted, its amendments, and its climate designation. There is no universal rule and this page publishes none.- Wind
Junctions are also load paths. Building America’s bracing guide states that dormers “can add significant additional uplift and torsional loads to the main roof and the rest of the house,” and warns that “often there aren’t engineering specifications for the connection in this area or attention to ensure it is as strong and robust as all other roof connections.” A wing or a dormer added later is exactly the case that guidance is describing.
Wind performance is site- and building-specific. Basic wind speed, exposure category, building height and geometry, pressure zone, enclosure classification, attachment schedule and the tested assembly all enter the answer, and none of them is settled by a roof shape or by a marketing mph figure. That determination is made by a registered design professional against the standard the jurisdiction has adopted.- Structural weight
Where a wing meets a main roof, the framing at the valley is not ordinary framing. Building America describes the problem with the short rafters that fill in a roof transition: “the compound miter angles of these rafters in the roof transition area necessitate a different kind of connector than straight rafters; thus, traditional rafter hangers cannot be used,” and because those rafters have no bearing or seat support, “the lower nail fastener must provide that bearing. As a result, it is not uncommon to see split wood at this connection.”
Nothing here is a structural determination for any building. Member sizes, spans, connections, loads and bracing adequacy are decided by a licensed design professional looking at the building in front of them, working to the code the local authority has adopted.- Code and jurisdiction
Every dimension quoted on this page comes from federal technical guidance or trade guidance, not from law. There is no nationwide building code for site-built construction in the United States. The Building America guides cited here reference the 2015 and 2018 editions of the model International Residential Code — including R903.2.1, R905.2.8.3 and the reroofing section R908.6 — and those are model provisions of editions that many jurisdictions have since superseded. They were never the law anywhere by themselves.
Confirm the edition your state or local government has adopted, the amendments it made, the effective date, and what is actually required on a permit with your authority having jurisdiction. A model code section number quoted on a website is not a determination for your address.- Maintenance
Combination roofs collect. A valley whose upslope end is a ridge termination is a natural debris trap; so is the pocket where a wing meets a wall. Debris holds water against a joint and, in cold climates, holds ice there. The maintenance obligation on a four-shape roof is not four times a two-plane roof’s, but it is different in kind: it is inspection of specific points rather than a look at a surface. All of it can be done from the ground with binoculars and a photograph taken after rain.
The junctions are usually outside the covering warranty and inside the workmanship oneSection link
This matters more on a combination roof than on any other shape, because the parts most likely to fail are the parts a shingle warranty was never about.
- A covering warranty covers the covering
Shingles, panels and membrane are the manufacturer’s product. Step flashing, apron flashing, counterflashing, kickouts and crickets are usually sheet metal fabricated or bought by the installer. A failure at a junction is therefore normally a workmanship question, and it is answered by the installer’s warranty and by the contract — not by the shingle wrapper.
- System warranties attach conditions at exactly these points
Where a manufacturer offers an enhanced or system warranty, it generally requires that manufacturer’s accessories and its published application instructions, and the accessories in question are disproportionately the transition components. Read which junction details are named, and whether the proposal in front of you actually includes them.
- Reused flashing is a live question at a re-roof
Building America’s guide for existing homes cites the model code’s reroofing section on flashings (2018 IRC R908.6) in the course of describing roof-wall work. Whether existing metal may be left in place where you live is set by the edition your jurisdiction adopted and by what the authority having jurisdiction accepts on the permit — but as a commercial question, “new flashing at every junction” and “reuse what is serviceable” are two different prices and should not be hidden inside one number.
Repairability
A field repair on a simple plane is a small job. A repair at a junction is a different problem: it usually means removing courses in two directions, lifting a section of siding or cutting a new reglet into masonry, and re-lapping the wall’s water management with the roof’s in the right order. That is why a junction repair costs more than its size suggests and why patching it with sealant is so common and so temporary.
The practical consequence for a combination roof is that the cheapest moment to correct any junction is when the covering is already off. If a re-roof is within a few years, junction work deferred to that date is usually money better spent than the same work done twice.
A warranty is a contract between a reader and whoever wrote it. What it covers, what voids it, whether it transfers, and how it is enforced are set by that document and by the law where the reader lives. Read the actual warranty for the product and the installer in front of you — not a summary of one, including this one.
Questions to ask an installerSection link
Every one of these is answerable from the ground, and every one of them is about a junction rather than about the field.
Walk me around the house and point at every place a roof plane meets a wall. What are you doing at each one?
This is the single most useful question on the page. A contractor who walks it with you and names step flashing here, an apron there, a kickout at that corner, is showing you the inventory in their head. One who says “we flash everything” has not counted.
Which valley method are you using, and why that one for this covering and this slope?
NRCA describes three basic valley types for asphalt shingle roof systems — woven, open and closed-cut — and says selection “is determined by material type, roof plane slope, climate and aesthetic expectations.” A specific answer that mentions two of those four inputs is a good sign. “Whatever we normally do” is not.
Where will the kickouts be, and will I be able to see them when you are finished?
Kickouts are small, cheap, frequently omitted, and the damage from omitting one happens inside a wall. Being told where they will be gives you something you can check from the driveway afterwards.
Is the flashing new at every junction, or are you reusing what is there? Which ones, and why?
Both answers can be legitimate. Only one of them is a lower price, and you should know which you are buying before you compare it with someone else’s number.
What is the slope on the rear addition, and is the covering you are quoting rated for it?
Building America states that asphalt shingles “should only be installed on roof slopes of 2 in 12 or greater,” with a double underlayment application required from 2:12 up to 4:12. A shallow addition is where a single-covering quote quietly stops being appropriate.
Who removes and reinstates the siding at the sidewalls, and what happens if there is damage behind it?
Correct step flashing has to be integrated with the wall’s drainage plane, which usually means disturbing cladding. Whether that is in the roofing scope, in a separate trade’s scope, or in nobody’s scope is a real source of disputes and of change orders.
Is there a cricket behind the chimney, and is it in this price?
The model IRC sets a chimney-width threshold above which a cricket is required; that model figure is quoted, with the edition it comes from, on the complex geometry page. Model text is not the law anywhere by itself — what binds you is the edition your jurisdiction adopted, as amended, as its authority having jurisdiction reads it. Regardless of the requirement, the upslope face of a wide chimney collects water, snow and debris against a flashing joint if nothing splits the flow.
Require these in writing
- Every roof-to-wall run identified by location and approximate length, with the flashing type named for each.
- The valley method named for each valley, and the underlayment used in it.
- The number and locations of kickouts.
- New versus reused flashing, stated location by location rather than as a general policy.
- The slope of every plane and the covering assigned to each, where the roof has more than one slope.
- Cricket, saddle and counterflashing work as separate priced items rather than “as needed”.
- What happens to siding, gutters and downspouts that have to come off, and who reinstates them.
- The unit rate and allowance for deck repair found at a junction once the covering is off.
Misconceptions and failure modesSection link
Five beliefs that make a combination roof harder to buy, and five ways these roofs actually fail.
Common misconceptions
Common belief
My house has a hip roof.
What is actually true
It probably has a hip roof and something else. In the two counties the one study of this kind classified from satellite imagery, 72 percent and 63 percent of single-family houses were classified as having complex roofs rather than simple ones. Naming the dominant shape is useful shorthand and a poor basis for a scope of work — the parts that were left out of the shorthand are usually the parts with the junctions in them.
Common belief
A combination roof is a design style someone chose.
What is actually true
Sometimes. More often it is a record of the building’s history: a garage attached in one decade, a rear extension in another, a dormer cut in later still. That matters practically, because the junction between two eras of construction is where two different sets of assumptions, materials and standards of care meet.
Common belief
More shapes means more roof, so it costs more per square foot.
What is actually true
Complexity adds surprisingly little area. What it multiplies is edge — lineal feet of valley, hip, and wall junction — and edge is priced by the foot and by the detail, not by the square. That arithmetic is worked through properly on the complex geometry page, which is where the multiplier belongs.
Common belief
It all has the same shingles, so it is all the same roof.
What is actually true
A matching covering says nothing about what is underneath it. An addition may sit on a different deck, at a different slope, under a different underlayment, built to a different code vintage, with or without an ice barrier. The visible surface is the one part of the assembly a later crew could easily make consistent.
Common belief
An aerial photo tells me what I need to know about my roof.
What is actually true
It tells you the shapes and the lines, which is genuinely most of what this page is asking for. It tells you nothing about whether the step flashing is lapped under the housewrap or over it, whether there is underlayment in the valley, whether a kickout exists behind the gutter, or what the deck is doing. Those are the questions the inventory is for — it produces them, it does not answer them.
How it actually fails
- No kickout where a sidewall reaches the eave
- Everything that ran down the roof-to-wall junction arrives at the bottom of it and, with nothing to turn it, runs down the face of the wall and in behind the cladding. Building America describes the consequence: “if sidewall flashing is lacking or inadequate, water can leak into the wall and cause serious water damage,” and adds that “new wall claddings like fiber cement, vinyl siding, and brick veneer can mask the evidence for years.”What you can see: A stain, streak or growth on the wall directly below where a roof edge meets it. Paint failing in a vertical band under that corner. Trim at the bottom of that wall softening before the trim anywhere else does.
- An addition tied in below the covering’s minimum slope
- A rear or side addition is built shallower than the main roof because of head height, and the same shingles are carried across it. Building America is explicit that asphalt shingles “should only be installed on roof slopes of 2 in 12 or greater” and that from 2:12 to 4:12 a double underlayment application is required. A lapped, water-shedding system laid below its slope range is being asked to behave like a membrane.What you can see: A visibly flatter plane on a newer part of the house. Standing water or a persistent dirt tide line on it after rain. Repeated repairs to the same small area of an addition ceiling.
- Old flashing reused at a junction during a re-roof
- Removing and replacing flashing at a sidewall means disturbing cladding; leaving it means the new covering is lapped onto metal whose fastener holes, laps and corrosion belong to the previous roof. It is the cheapest corner to cut on a combination roof because the saving is invisible on the day.What you can see: Bright new shingles meeting dull, dented or previously bent metal at a wall. Sealant smeared along a wall junction on an otherwise new roof. A proposal that prices the covering in detail and says nothing about flashing.
- A dormer or wing connection nobody engineered
- Building America’s bracing guide states that dormers “can add significant additional uplift and torsional loads to the main roof and the rest of the house,” and that “often there aren’t engineering specifications for the connection in this area.” The same guide notes that the short rafters filling a roof transition have no bearing or seat support, so “it is not uncommon to see split wood at this connection.”What you can see: Nothing reliable from the ground, which is the point. Repeating cracks in the ceiling or wall finishes around a dormer after wind events are worth reporting to a professional; the connection itself is only assessable by someone who can see the framing.
- A pocket with nowhere to drain where a wing meets a wall
- Where two shapes were joined without anyone working through the drainage, the geometry can leave a corner with little or no fall — water arrives and has no line to follow. A shedding covering depends on slope; a pocket asks it to hold water. The correct answer is usually a low-slope assembly detailed as one, or a cricket built to give the water a slope, rather than more sealant.What you can see: A dark patch that stays dark for a day or two after everyone else’s roof has dried. Debris and leaves that never clear from one corner. Moss or algae concentrated in one pocket rather than spread over a plane.
Sources and further readingSection link
Understanding Roofing / Published
Scope and limitations
- It cannot tell you what shapes your roof is made of.
- It gives you a method for finding out from the ground; the answer is a fact about your building.
- It cannot tell you whether any junction on your roof is correctly detailed.
- Almost everything that decides that is under the covering or behind the cladding, and it is not visible from the ground, from a photograph, or usually from the roof either.
- It publishes no cost figure.
- Roof shape moves a price through complexity, waste, flashing count, and production speed, but no transparent national dataset separates the shape from the covering, the building, and the market.
- It publishes no national statistic for how many houses are hybrids.
- No federal inventory records residential roof shape.
- The two counties cited below are coastal, hurricane-prone, classified by a machine-learning model from satellite imagery, and between 11 and 17 percent of their houses could not be classified at all.
- That same measurement counts only gable-family and hip-family shapes.
- A house whose complication is a shed addition, a porch roof, or a flat section is not described by its categories, so the figures cannot be read as a count of combination roofs in the sense this page uses.
- It states no code requirement.
- Every dimension quoted here comes from federal or trade guidance citing model provisions of the 2015 and 2018 IRC — editions many jurisdictions have superseded, and model text was never law anywhere by itself.
- It makes no structural determination.
- Dormer and wing connections, valley framing, and the loads at a transition are questions for a licensed design professional looking at the building.
- It is not an inspection and does not replace one.
- The inventory it produces is a list of questions to put to a contractor or an inspector.
Automatic Roof Type Classification Through Machine Learning for Regional Wind Risk Assessment (arXiv:2305.17315)
Shuochuan Meng, Mohammad Hesam Soleimani-Babakamali and Ertugrul Taciroglu, University of California, Los Angeles — preprint submitted to Advanced Engineering Informatics / Preprint dated 27 May 2023
That roof type is “the most frequently missing building feature from publicly available databases”; that roof types were predicted for 161,772 single-family houses in New Hanover County, North Carolina and Miami-Dade County, Florida; that the paper defines five roof types — listed in one sentence as “simple gable, simple cross-gable, complex gable, simple hip, and cross-hip”; that “regarding roof complexity, 72% and 63% of houses have complex roofs (i.e., simple cross-gable, complex cross-gable, and cross-hip) in New Hanover County and Miami-Dade County, respectively”; and that “roof types for 17% and 11% of houses in New Hanover County and Miami-Dade County were classified as unknown.”
Academic research used here for triangulation only, and it is not a national statistic: both study areas are coastal, hurricane-prone counties, roof types were assigned by a machine-learning classifier from satellite imagery, and 11 to 17 percent of houses could not be classified. Its category labels are not identical between the sentence defining the five types and the sentence reporting complexity — “complex gable” in one, “complex cross-gable” in the other — and both are reported here as printed. Its taxonomy contains only gable-family and hip-family shapes, so it does not count shed additions, porch roofs, or flat sections at all. It says nothing about any individual building.
Step and Kick-Out Flashing at Roof-Wall Intersections
U.S. Department of Energy, Building America Solution Center (PNNL)
The instruction to install step and kick-out flashing at all roof-wall intersections to protect walls from water intrusion; that step flashing should extend “at least 4 inches up the wall from the roof deck and at least four inches out along the roof deck”, be installed in shingle fashion, and be integrated with the wall drainage plane; the instruction to “install kick-out flashing at the end of a roof-wall intersection to divert water away from the wall and into gutters”; that in multi-level house designs the roof-wall intersection channels much of the roof’s water and that “if sidewall flashing is lacking or inadequate, water can leak into the wall and cause serious water damage”; and that “new wall claddings like fiber cement, vinyl siding, and brick veneer can mask the evidence for years.”
Best-practice guidance for builders, not adopted law. The dimensions it gives are cited to the 2015 IRC, and it also references the 2009, 2012 and 2018 IRC — model provisions of editions many jurisdictions have superseded. It establishes nothing about what is required at any address.
Flashing of Roof-Wall Intersections in Existing Homes
U.S. Department of Energy, Building America Solution Center (PNNL)
That the fundamental principle of water management is “to shed water by layering materials in such a way that water is directed down, out, and away from the building”; that the guide covers “transitions to those assemblies such as lower roofs, porch roofs, decks, balconies, railings, and dormers”, including wall-to-lower-roof transitions; and that it cites the 2018 IRC sections R903.2.1, R905.2.8.3 and R908.6 (reroofing flashings).
Retrofit guidance, not adopted law, and its code citations are to a model edition. This page does not reproduce the text of R908.6 — it records only that the guide cites it — because the ICC code site blocks automated retrieval and the section text was not read directly.
Roof Valleys and Penetrations Sealed
U.S. Department of Energy, Building America Solution Center (PNNL)
That “valleys and penetrations through the roof decking are among the most vulnerable areas for water intrusion”; that valleys should be carefully sealed along their entire length with a self-sealing bituminous membrane or equivalent, properly integrated into the adjoining roofing materials; and that because roof valleys are difficult to ventilate they are more prone to heat accumulation and therefore to snow melt, which can contribute to ice dam formation and subsequent water leakage.
Programme-oriented best-practice guidance. It does not compare open, closed-cut and woven valley methods, and it is not a determination of what any jurisdiction requires.
Bracing of Roofs for Hurricane, High Wind, and Seismic Resistance
U.S. Department of Energy, Building America Solution Center (PNNL)
That dormers “can add significant additional uplift and torsional loads to the main roof and the rest of the house”; that “often there aren’t engineering specifications for the connection in this area or attention to ensure it is as strong and robust as all other roof connections”; that “the compound miter angles of these rafters in the roof transition area necessitate a different kind of connector than straight rafters; thus, traditional rafter hangers cannot be used”; and that because those rafters lack bearing or seat support, “the lower nail fastener must provide that bearing. As a result, it is not uncommon to see split wood at this connection.”
Best-practice guidance for high-wind and seismic construction, not adopted law and not a structural design. It does not establish member sizes, connector schedules, or adequacy for any specific building.
Asphalt Shingle Roofs
U.S. Department of Energy, Building America Solution Center (PNNL)
That asphalt shingles “should only be installed on roof slopes of 2 in 12 or greater”, and that “for roof slopes from 2 in 12 up to 4 in 12, a double underlayment application is required”; and the instruction to properly flash all roof penetrations and roof-wall intersections.
Guidance citing the 2018 IRC and programme standards, not the law in any jurisdiction. Minimum slope for a specific product is set by that product’s published application instructions and by the adopted code, and both can be more restrictive than a general guidance figure.
Chimneys Connected to Roof Structure
U.S. Department of Energy, Building America Solution Center (PNNL)
That “where sloping roofs intersect the upper vertical surface of the brick layer enclosing the chimney flue, a cricket or saddle flashing should be installed to redirect rainwater that is draining down the roof slope around the chimney”; and that counterflashing is “embedded into the mortar joints of the brick layer and overlaps the base flashing and the step flashing, completing the waterproofing transition.”
The guide gives no chimney width at which a cricket becomes mandatory, and this page therefore states none. That threshold and its exceptions belong to the code edition adopted locally. Its code references are to the 2018 IRC and to California-specific documents.
In the valley
Tom Bollnow, Professional Roofing (National Roofing Contractors Association) / March 2013
That “the three basic valley types for asphalt shingle roof systems are woven, open and closed-cut”, with variations known as California valleys; that “selection of valley type is determined by material type, roof plane slope, climate and aesthetic expectations”; that “key points in all valley details are the upslope end where it terminates (ridge, dormer crest and unequal rafter lengths) and the down-slope end (eave, dormer to interface and intersection with side wall)”; and NRCA’s recommendations that valley metal be formed with a centre-line rib at least 1 inch high and 24 inches wide in lengths no longer than 10 feet, over a full-width sheet of polymer-modified bitumen underlayment.
Trade guidance published in 2013 and not adopted law. NRCA recommendations are the association’s own; they do not override a manufacturer’s published application instructions or an adopted code, and this page does not reproduce the article’s dimensional recommendations as requirements.
Metal Flashing (RICOWI Roof Guide)
Insurance Institute for Business & Home Safety
That “the primary function of roof flashing is to shed or direct water away from roof edges and penetrations to prevent infiltration into the building”; that metal flashing is used at parapet copings, roof perimeters, wall-to-roof transitions, valleys where slopes intersect, and penetrations such as chimneys and vents; and that “valley flashing is used to prevent water infiltration where two sloping planes of a roof intersect.”
Cited undated: the guide page carries no publication date of its own, and the June 2019 date visible near it belongs to a different guide in the same series. It is one of the RICOWI roof guides hosted by IBHS, a research organisation funded by the insurance industry. It is not a code, not a test standard, and not a determination about any building or product.
Fall Protection in Residential Construction
U.S. Occupational Safety and Health Administration
That “falls are the leading cause of death for workers engaged in residential construction”, and that “workers engaged in residential construction six (6) feet or more above lower levels must be protected by conventional fall protection.”
OSHA standards regulate employers and their workers. They do not apply to a homeowner on their own house — which is precisely why a homeowner has none of the training, equipment, or supervision the standard assumes, and why the safe method on this page is a ground-based one.
How do I know if I have asbestos in my home? (floor tile, ceiling tile, shingles, siding, etc.)
U.S. Environmental Protection Agency
That “the only way to be sure whether a material contains asbestos is to have it tested by a qualified laboratory”, and EPA’s advice to have suspect material tested if it is damaged or if a planned renovation would disturb it, with samples collected by a qualified, accredited inspector.
General homeowner guidance. It does not establish that any particular roofing material contains asbestos, and the age of a building is not determinative either way. Abatement and disposal requirements are set by federal, state and local rules.