A hip roof buys wind performance with framing labour and ridge length.
Steep-slope · single-family and small multifamily
It slopes on all four sides, so there is no gable end wall to blow in. The price is paid in cut lines, cap shingles, and an attic that is much harder to exhaust.
Is a hip roof better than a gable roof?
A hip roof slopes on all four sides, so it has no gable end wall — no tall vertical face at either end. Wind-tunnel work summarised by the Department of Energy puts peak wind-induced pressures as much as 50 percent below a comparable gable roof. It costs more because it is cut, not because it is bigger: over the same footprint at the same pitch, the roof area is identical.
The short versionSection link
Every figure below is derived from one worked geometry: a 40 ft × 28 ft rectangular footprint framed at 6:12 on every plane, with no dormers and no wings. Change the footprint and the numbers change; the direction they move in does not.
- Roof surface area
- Identical to a gable1,252 sq ft either way, because both roofs are the same footprint multiplied by the same pitch factor of 1.118. A hip roof is not a bigger roof.
- Ridge length
- 12 ft, against 40 ftA hip ridge is the long dimension minus the short one. On a square footprint it reaches zero. This single number drives the ventilation problem.
- Line needing hip and ridge cap
- 96 lin ft, against 40 lin ft12 ft of ridge plus four 21 ft hips. 2.4 times the cap, and 84 lin ft of angled cut through the shingle field that a gable roof does not have.
- Peak wind-induced pressure
- As much as 50% lowerWind-tunnel finding reported by DOE's Building America Solution Center, citing Meecham (1992) and Shao et al. (2018). A pressure reduction, not immunity.
- Enclosed attic volume
- About 23% less3,005 cu ft against 3,920 cu ft on this footprint. Full standing height exists only over the 12 ft ridge.
| Quantity | Gable | Hip | What it drives |
|---|---|---|---|
| Roof surface area | 1,252 sq ft | 1,252 sq ft | Field material and tear-off. Identical — this is the number people assume differs, and it does not. |
| Ridge | 40 lin ft | 12 lin ft | Continuous run available for a ridge vent, and for ridge cap. |
| Hips | 0 | 84 lin ft (4 × 21 ft) | Hip rafters, jack rafters, angled cut line, hip cap, and hip-vent capacity. |
| Line requiring hip and ridge cap | 40 lin ft | 96 lin ft | Accessory material and the labour to lay it. 2.4×. |
| Rake edge | 62.6 lin ft (4 × 15.65 ft) | 0 | Rake trim and drip edge on the gable; the hip roof spends nothing here. |
| Eave and gutter line | 80 lin ft | 136 lin ft | Gutter, drip edge, and — the one place hip geometry helps ventilation — soffit available for intake. 1.7×. |
| Angled cut line through the field | 0 | 84 lin ft | Every course on every plane dies into a hip at a compound angle. This is where hip cut waste comes from. |
| Vertical gable end wall | 2 × 98 sq ft, 7 ft tall at the peak | None | The face that catches wind, and the element FEMA's wind retrofit guide names as a retrofit in its own right — the 2010 first edition set the bracing threshold at 4 ft tall. |
| Enclosed attic volume | 3,920 cu ft | 3,005 cu ft | Storage, future conversion, and the volume the ventilation has to serve. |
| Framing members | Common rafters or trusses throughout | 4 hip rafters plus jack rafters on every plane | Cutting time, layout time, and the skill level the crew needs. |
Read this table one item at a time
Roof surface area
- Gable
- 1,252 sq ft
- Hip
- 1,252 sq ft
- What it drives
- Field material and tear-off. Identical — this is the number people assume differs, and it does not.
Ridge
- Gable
- 40 lin ft
- Hip
- 12 lin ft
- What it drives
- Continuous run available for a ridge vent, and for ridge cap.
Hips
- Gable
- 0
- Hip
- 84 lin ft (4 × 21 ft)
- What it drives
- Hip rafters, jack rafters, angled cut line, hip cap, and hip-vent capacity.
Line requiring hip and ridge cap
- Gable
- 40 lin ft
- Hip
- 96 lin ft
- What it drives
- Accessory material and the labour to lay it. 2.4×.
Rake edge
- Gable
- 62.6 lin ft (4 × 15.65 ft)
- Hip
- 0
- What it drives
- Rake trim and drip edge on the gable; the hip roof spends nothing here.
Eave and gutter line
- Gable
- 80 lin ft
- Hip
- 136 lin ft
- What it drives
- Gutter, drip edge, and — the one place hip geometry helps ventilation — soffit available for intake. 1.7×.
Angled cut line through the field
- Gable
- 0
- Hip
- 84 lin ft
- What it drives
- Every course on every plane dies into a hip at a compound angle. This is where hip cut waste comes from.
Vertical gable end wall
- Gable
- 2 × 98 sq ft, 7 ft tall at the peak
- Hip
- None
- What it drives
- The face that catches wind, and the element FEMA's wind retrofit guide names as a retrofit in its own right — the 2010 first edition set the bracing threshold at 4 ft tall.
Enclosed attic volume
- Gable
- 3,920 cu ft
- Hip
- 3,005 cu ft
- What it drives
- Storage, future conversion, and the volume the ventilation has to serve.
Framing members
- Gable
- Common rafters or trusses throughout
- Hip
- 4 hip rafters plus jack rafters on every plane
- What it drives
- Cutting time, layout time, and the skill level the crew needs.
Arithmetic, not a price. Pitch factor is √(1 + (6/12)²) = 1.118. Hip rafter length is √(14² + 14² + 7²) = √441 = 21 ft exactly on this geometry. Attic volumes are ½ × 28 × 7 × 40 for the gable and ⅓ × 28² × 7 + 12 × (28 × 7 ÷ 2) for the hip. Nothing here converts to dollars, and the cost section explains why this page does not attempt it.
Where a hip roof earns its premium, and where it does notSection link
Best when
- Wind is the governing hazard where the building is, and the budget also covers deck attachment, roof-to-wall connectors, and opening protection — the items that fail before shape matters.
- The house is in a market where a wind-mitigation credit is a defined, verifiable thing rather than a hope. Florida is the clearest example: the state's inspection form has a written definition of a hip roof.
- The building is on an exposed site with no attic conversion planned and no large solar array planned.
- You want gutter on all four sides and no rake edge to maintain.
- The design already has a rectangular footprint long enough that the ridge does not vanish. A hip over a square plan has no ridge at all.
Think twice if
- The attic is storage you use, or is a candidate for conversion later. You lose roughly a quarter of the volume and nearly all of the full-height floor area.
- A large rooftop solar array is planned. Hip planes are trapezoids and triangles, and contiguous rectangular array space is exactly what they lack.
- The exhaust ventilation design is being left to the roofer to sort out on the day. A 12 ft ridge does not carry a 1,120 sq ft attic, and the fix has to be specified before the roof is closed.
- The pitch is below the minimum the hip-vent product requires. One manufacturer publishes a 5:12 minimum overall pitch for hip applications of its ridge vents — below that, hip venting is off the table for that product.
- The money is finite and the roof deck is stapled. Re-nailing the deck and sealing it are cheaper than reframing a roof, and they are the first things in FEMA's Basic Mitigation Package — the package its current wind retrofit guide says everything else builds on.
What changes the answer
- Footprint proportions. Ridge length is long dimension minus short dimension, so a 60 × 28 house keeps 32 ft of ridge and a 30 × 30 house keeps none.
- Whether the comparison is against a braced gable or an unbraced one. FEMA's guidance is not 'gables fail' — it is that gable ends need connections and bracing that a hip roof does not have to buy.
- Governing hazard. In a hail belt or a heavy-snow region, roof shape is not the variable doing the work, and the hip premium buys little.
- Whether the attic is vented at all. A correctly designed unvented assembly makes the ridge-length problem disappear — and introduces a different set of design questions.
- Whether anyone will actually verify the ventilation. The arithmetic below is only useful if the total net free area is written into the proposal.
The ridge is the number that explains everything elseSection link
Hip geometry does three things at once: it deletes the gable end wall, it converts two roof planes into four, and it shortens the ridge to the difference between the building's two dimensions. Wind performance comes from the first. Cost comes from the second. The ventilation problem comes from the third.
A hip roof slopes on every side. Where a gable roof ends in a triangular vertical wall, a hip roof ends in another sloping plane, and the line where two adjacent planes meet on an outside corner is a hip. That is the whole definition. Everything below follows from it.
What the wind evidence actually says
The Department of Energy’s Building America Solution Center compares the two shapes directly and reports that wind-tunnel testing by Meecham (1992) and Shao et al. (2018) found “peak wind-induced pressures can be as much as 50% lower in a hip roof versus a gable roof.” It lists “performs better in high winds and extreme weather” as a hip advantage and “prone to damage from uplift and racking in high winds” as a gable disadvantage.
Read that carefully. It is a statement about pressure, on a tested shape, in a wind tunnel. It is not a rating, it is not a wind speed, and it is not a code determination. Wind design for a real building depends on basic wind speed, exposure category, mean roof height, enclosure classification, risk category, the pressure zone a given piece of roof falls in, the attachment schedule, and the tested assembly — and a shape is one input to that, not a substitute for it. A 50 percent reduction in peak pressure on a roof whose sheathing is stapled and whose rafters are toe-nailed still ends with the roof in the neighbour’s yard.
The second half of the evidence is about what a hip roof does not have. FEMA’s Wind Retrofit Guide for Residential Buildings (P-804) has treated the gable end as a thing needing retrofit since its first edition. That edition, December 2010, states in Section 4.1.4 that “gable end walls are particularly vulnerable to damage in high-wind events due to their structural configuration,” and that “loads created by high winds can quickly overwhelm the capacity of gable end walls that do not have adequate structural connections.” It devotes a section to strengthening overhangs at gable end walls and a further section, 4.2.2, to bracing gable end walls four feet tall or more. On the geometry drawn above, the gable end wall is seven feet tall at the peak — comfortably into that category.
That first edition has been superseded. FEMA published a second edition of P-804 in 2023, and FEMA’s own advisory on it says the update replaces the 2010 guide. The wording above belongs to the 2010 edition and is quoted as such; what carries forward is the substance, because “strengthening gable end walls” is still a named retrofit in the second edition — sitting in its Intermediate Mitigation Package, after the Basic package that deals with the roof deck. Section and figure numbers from the 2010 edition should not be quoted as though they were the current document’s.
A hip roof has none of that work to do, because it has no gable end. But note what FEMA is really saying: gable ends are vulnerable when they lack adequate connections and bracing. That is a retrofit instruction, not a verdict on the shape. A properly braced gable end is a solved problem. An unbraced one is the thing the hip roof is being compared against.
And the hip roof does not escape pressure zones. The 2010 edition’s figure showing enhanced sheathing-fastening zones is captioned “4-foot end zones on gable and hiproofs” — the enhanced fastening applies to both. Corners and edges carry the highest uplift on both shapes. Hip geometry lowers the peaks; it does not move them somewhere else.
Why it costs more, given that it is not bigger
This is the part most comparisons get wrong. Over the same footprint at the same pitch, a hip roof and a gable roof have the same surface area. Both are the plan area multiplied by the same pitch factor. On the worked geometry that is 1,120 × 1.118 = 1,252 sq ft, or 12.5 roofing squares, either way. If a quote prices a hip roof as though there were more roof, ask to see the takeoff.
The premium is real, and it lives in four places:
- Framing. Four hip rafters, each cut with a compound bevel at both ends, plus a jack rafter of a different length landing on every one of them. BASC describes hip roofs as “comparatively more complicated to design and build” and “more expensive than gable roofs.” A truss package solves the layout but does not make the roof cheaper.
- Cap. 96 lineal feet of hip and ridge cap against 40. Cap is a separate product, laid one piece at a time, with its own nailing pattern.
- Cut waste. 84 lineal feet of angled cut line that a gable roof does not have. Every course on every plane dies into a hip at an angle, and most of the offcut is not reusable. How much waste factor that justifies is an estimator’s judgement on the actual roof, and this page will not invent a percentage for it — but the cut line is a measurable quantity, and it belongs in the conversation.
- Labour, not material. Three of those four are time. That is why the hip premium moves with the local labour market rather than with material prices, and why a national percentage would be meaningless.
The gable roof spends money the hip roof does not, too: 62.6 lineal feet of rake edge with its trim and drip edge, and two gable end walls that need cladding, flashing, and — in a high-wind region — bracing. The gap is not as wide as the framing complexity alone suggests.
The attic you do not get
Enclosed volume drops from 3,920 to 3,005 cubic feet on this footprint, about 23 percent. The more useful number is where the headroom goes: on a gable, full standing height runs the whole 40 ft length under the ridge. On a hip, it exists only over the 12 ft of ridge, because the two ends are now sloping planes closing down to the eave. BASC lists “less attic storage space due to slopes on all sides” as a hip disadvantage and “lots of attic storage” and “easier to make into additional living space” as gable advantages.
It also lists “reduced space for solar PV panels” as a hip disadvantage. The mechanism is the same one: the two end planes are triangles and the two long planes are trapezoids, so the largest rectangle you can fit on any of them is smaller than the plane itself.
Why a 12-foot ridge cannot exhaust an 1,120 square foot atticSection link
Same house, same attic, same code. The only thing that changed is how much ridge there is to put a vent on. This is the calculation that should happen before a hip roof is specified, and usually does not.
Start with the requirement. The model residential code provision sets a base net free area of 1/150 of the vented space, with an exception permitting 1/300 where both of its conditions are met: not less than 40 percent and not more than 50 percent of the required area sits in the upper portion, no more than 3 feet below the ridge, and — in Climate Zones 6, 7 and 8 — a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling. DOE’s Building America Solution Center gives the arithmetic: attic area divided by the ratio, then multiplied by 144 to get square inches.
required NFA (sq in) = attic area (sq ft) ÷ ratio × 144
The attic under the worked geometry is 40 × 28 = 1,120 sq ft. So:
- At 1/150: 1,120 ÷ 150 = 7.47 sq ft = 1,075 sq in total.
- At 1/300: 1,120 ÷ 300 = 3.73 sq ft = 538 sq in total, of which 40–50 percent — 215 to 269 sq in — must sit in the upper portion.
Now the supply. Net free area per lineal foot is a manufacturer-published, product-specific figure; one manufacturer publishes 20, 13.5, and 12 square inches per lineal foot across three of its ridge vent lines. Take 13.5 as a mid-range illustration — substitute the actual product’s figure when you do this for a real roof, because the answer scales directly with it.
| Line item | Gable roof | Hip roof | Where the number comes from |
|---|---|---|---|
| Attic area to be vented | 1,120 sq ft | 1,120 sq ft | 40 ft × 28 ft footprint. Identical. |
| Ridge available for a continuous vent | 40 lin ft | 12 lin ft | Hip ridge = long dimension − short dimension. |
| Hip line available for a hip vent | None | 84 lin ft — but only 36 lin ft of it (9 ft per hip) lies within 3 vertical feet of the ridge | Each hip is 21 ft; height falls linearly from 7 ft to 0, so the band above 4 ft is the top 3/7. |
| Exhaust NFA from the ridge at 13.5 sq in per lin ft | 540 sq in | 162 sq in | Lineal feet × the product's published figure. |
| Total required NFA at 1/150 | 1,075 sq in | 1,075 sq in | 1,120 ÷ 150 × 144. |
| Exhaust share of a balanced 50/50 split | 538 sq in needed — the ridge supplies 540, or 100% | 538 sq in needed — the ridge supplies 162, or 30% | Intake must be at least equal to exhaust, per the vent manufacturer and IIBEC. |
| Shortfall to be made up elsewhere | None | 376 sq in — about 28 more lineal feet of vented line that does not exist on the ridge | 538 − 162, divided by 13.5. |
| Upper-portion NFA if the 1/300 route is used | 215–269 sq in needed; 16–20 ft of the 40 ft ridge supplies it | 215–269 sq in needed; the whole 12 ft ridge supplies only 162 | 40–50% of 538 sq in, divided by 13.5. |
| Soffit line available for intake | 80 lin ft | 136 lin ft | Eave perimeter. The one ventilation metric the hip roof wins, by 70%. |
Read this table one item at a time
Attic area to be vented
- Gable roof
- 1,120 sq ft
- Hip roof
- 1,120 sq ft
- Where the number comes from
- 40 ft × 28 ft footprint. Identical.
Ridge available for a continuous vent
- Gable roof
- 40 lin ft
- Hip roof
- 12 lin ft
- Where the number comes from
- Hip ridge = long dimension − short dimension.
Hip line available for a hip vent
- Gable roof
- None
- Hip roof
- 84 lin ft — but only 36 lin ft of it (9 ft per hip) lies within 3 vertical feet of the ridge
- Where the number comes from
- Each hip is 21 ft; height falls linearly from 7 ft to 0, so the band above 4 ft is the top 3/7.
Exhaust NFA from the ridge at 13.5 sq in per lin ft
- Gable roof
- 540 sq in
- Hip roof
- 162 sq in
- Where the number comes from
- Lineal feet × the product's published figure.
Total required NFA at 1/150
- Gable roof
- 1,075 sq in
- Hip roof
- 1,075 sq in
- Where the number comes from
- 1,120 ÷ 150 × 144.
Exhaust share of a balanced 50/50 split
- Gable roof
- 538 sq in needed — the ridge supplies 540, or 100%
- Hip roof
- 538 sq in needed — the ridge supplies 162, or 30%
- Where the number comes from
- Intake must be at least equal to exhaust, per the vent manufacturer and IIBEC.
Shortfall to be made up elsewhere
- Gable roof
- None
- Hip roof
- 376 sq in — about 28 more lineal feet of vented line that does not exist on the ridge
- Where the number comes from
- 538 − 162, divided by 13.5.
Upper-portion NFA if the 1/300 route is used
- Gable roof
- 215–269 sq in needed; 16–20 ft of the 40 ft ridge supplies it
- Hip roof
- 215–269 sq in needed; the whole 12 ft ridge supplies only 162
- Where the number comes from
- 40–50% of 538 sq in, divided by 13.5.
Soffit line available for intake
- Gable roof
- 80 lin ft
- Hip roof
- 136 lin ft
- Where the number comes from
- Eave perimeter. The one ventilation metric the hip roof wins, by 70%.
Arithmetic, not a code determination. 13.5 sq in per lineal foot is one manufacturer's published figure for one product, used as an illustration; net free area is product-specific and the whole table scales with it. The 1/150 and 1/300 ratios are model code language read in an adopted state code and confirmed by NRCA, IIBEC and DOE BASC — the edition, amendments, and effective date that apply to your building come from your building department, not from here. A correctly designed unvented attic assembly needs none of this and is an equally legitimate approach.
What the table actually tells you
The gable roof’s ridge does the whole job by itself and then some. The hip roof’s ridge does about a third of it. That gap is not a detail to be resolved on site; it is a design decision that has to be made before the roof is closed, because retrofitting exhaust into a finished hip roof means pulling cap and cutting sheathing beside a structural rafter.
There are three honest routes out of it, and they are not interchangeable:
- Vent the hips. 84 lineal feet of hip line is plenty of raw length — 36 lineal feet of it at 13.5 sq in per foot is 486 sq in on its own. IIBEC notes that hip ridge vents can be installed along the hip lines of a hip roof and that hip-specific products now exist, designed to address the weather-infiltration problem that made the practice inadvisable with ordinary ridge vent. The constraint to check first is pitch: one manufacturer requires a 5:12 minimum overall roof pitch for hip applications.
- Use a single different exhaust strategy sized to the whole load. IIBEC also lists powered options. What matters is that it is one strategy. Adding box vents to a roof that already has ridge or hip vents produces the short circuit described below, where the high vents feed each other instead of pulling air from the soffits.
- Design the attic unvented. IIBEC notes that since the 2009 IRC an attic can be designed vented or unvented, and that the decision is a design choice rather than a code mandate. An unvented assembly makes ridge length irrelevant — and introduces its own questions about insulation type, vapor control, and climate zone that belong on the ventilation guide and to a qualified designer.
What is not a route: installing a ridge vent on 12 feet of ridge, noting that a ridge vent has been installed, and moving on. That is the most common outcome, and it is the reason this arithmetic is on this page.
One nuance worth carrying into a conversation with an inspector. Under the 1/300 route the upper ventilators must sit no more than 3 feet below the ridge. On the worked geometry only the top 9 feet of each hip — 36 of the 84 lineal feet — satisfies that. Run hip vent further down the hip and the extra area still ventilates, but whether it counts toward the upper-portion share is a question for the authority having jurisdiction, not for this page.
When the advice on this page is the wrong adviceSection link
A page that recommends a shape for wind performance should be explicit about the conditions under which that recommendation wastes a reader's money.
When the money should go somewhere else entirely
If wind is the governing hazard and the budget is finite, roof shape is rarely the highest-return place to spend it. The Mitigation Packages in the current second edition of FEMA P-804 are built from deck attachment and sealing, eave underlayment details, wind-resistant coverings, attic-vent water intrusion resistance, opening and garage door protection, soffit and chimney strengthening, gable-end strengthening, and a continuous load path — not from changing the shape of the roof. A hip roof with 6d-nailed sheathing and toe-nailed rafters is not a wind-resistant roof; it is a wind-resistant shape sitting on a weak assembly. Re-nailing a deck and sealing it during a re-roof costs a fraction of reframing, and it addresses the layer that actually fails.
When the comparison is not fair
The 50 percent pressure figure compares shapes, and FEMA’s gable warning is explicitly about gable ends without adequate structural connections. A gable end that has been braced the way FEMA’s 2010 guide describes — retrofit studs strengthening the vertical framing, horizontal braces at the top and bottom transferring lateral load into the roof and ceiling diaphragms, strap connections between the two, and metal brackets tying the bottom to the wall below — is a different building from the one in that warning. If the choice is between an engineered, braced gable and a hip, the wind argument narrows considerably, and the other columns of the tradeoff start to matter more.
When the hazard is something else
Hail does not care about roof shape; impact resistance is a covering and assembly question. Heavy snow is a load question answered by structure. Wildfire is about assembly class, ember entry at vents and eaves, and materials. In those regions the hip premium buys appearance, drainage, and gutter, and very little else. Shape is a wind-and-water variable.
When the attic is the point
If the attic is real storage, or a plausible future bedroom, a hip roof is the wrong shape and the arithmetic is not close: about a quarter less volume and full standing height only over the short central ridge. A gable roof gives a usable rectangular volume the full length of the building. The same logic applies to solar — BASC names reduced PV space as a hip disadvantage, and the reason is that trapezoids and triangles do not hold rectangular arrays efficiently.
When the plan is square
Hip ridge length is the long dimension minus the short one. On a square footprint that is zero, and the roof becomes a pyramid with no ridge at all. Every ventilation constraint on this page gets worse, and the exhaust design has to be settled before anything else about the roof is.
What would change our own answer
Two things. Published, current, transparent data on the actual installed-cost differential between the two shapes in specific labour markets — which would let this page replace a quantity takeoff with a real range. And a documented comparison of braced-gable against hip performance under equivalent design conditions, which would let it say something more precise than “the wind argument narrows.” If you have either, the corrections process is how this page changes.
What the shape actually costs, and why no dollar figure appears hereSection link
This block is a quantity takeoff, not a price. The hip premium is almost entirely labour, and labour rates are local — publishing a national percentage would be inventing the number this page exists to explain.
- Roof surface to cover
- 1,252 sq ft (12.5 squares)Identical to the gable. Field material and tear-off do not move.
- Hip and ridge cap line
- 96 lin ft vs 40 lin ft2.4×. Accessory material plus piece-by-piece labour.
- Eave and gutter line
- 136 lin ft vs 80 lin ft1.7×. More gutter and drip edge — and more soffit available for intake air.
- Enclosed attic volume
- 3,005 cu ft vs 3,920 cu ftAbout 23% less, and full standing height only over the 12 ft ridge.
- Units
- Lineal feet, square feet, and cubic feet for one worked geometry. No currency.
- Scope included
- Ridge, hip, rake and eave lines; capped line; angled cut line through the shingle field; roof surface area; and enclosed attic volume, for a 40 ft × 28 ft rectangular footprint at 6:12 on every plane, gable against hip.
- Not included
- Every labour rate, material price, accessory price, disposal fee, permit fee, and regional multiplier. Also excludes dormers, wings, valleys, chimneys and skylights, none of which exist on the worked geometry.
- Geography
- Geometry, not a market. The arithmetic holds anywhere; the rates it would be multiplied against do not.
- Data as of
- 26 August 2026 — the date this arithmetic was worked and checked.
- Confidence
- High for the arithmetic: it is exact for the stated geometry and re-derivable from the three inputs shown. Zero for any conversion into dollars, which this page deliberately does not attempt.
- Method
- How this figure is built
Three of the four drivers above are time rather than material: cutting and setting hip and jack rafters, laying 96 lineal feet of cap one piece at a time, and cutting every course into 84 lineal feet of angled hip line. A quote for a hip roof is therefore mostly a quote for hours, and hours are priced by the market the crew works in.
That is the honest reason there is no percentage here. A single national “hip roofs cost 15 to 20 percent more” figure is repeated widely and, as far as this page’s sourcing could establish, rests on nobody’s published dataset. What can be published is the takeoff, because the takeoff is what a competent estimator is pricing. Take these quantities into the cost section, or normalise real proposals against each other with the quote comparison guide.
One further caution about the money. BASC lists “potentially lower home insurance rates” as a hip advantage and attaches a savings range to it — but that range traces to a 2013 estimate by an insurance broker, and this page will not republish a thirteen-year-old broker figure as though it described anyone’s current premium. What can be stated is the regulatory mechanism, and it is in the considerations below.
A quantity takeoff is not a quote and this page publishes no price at all. The only number that binds anyone is the one in a signed scope of work for this building.
What changes this on a real buildingSection link
- Wind
Hip geometry lowers peak wind-induced pressure — as much as 50 percent lower in the wind-tunnel work DOE reports — and removes the gable end wall that the 2010 edition of FEMA’s wind retrofit guide called particularly vulnerable, and that the 2023 edition still treats as a retrofit worth naming. Both statements are about the shape. Neither is about your building.
What decides whether a real roof stays on is the chain beneath the shape: sheathing fastener type and spacing, a sealed deck, edge and underlayment details, soffits, opening protection, and a continuous load path. Those items, not roof shape, are what the Mitigation Packages in the current second edition of P-804 are built from — and the 2010 edition’s enhanced-fastening zones diagram covered “gable and hip roofs” alike.
Wind performance is site- and building-specific: basic wind speed, exposure, mean roof height, geometry, pressure zone, enclosure, risk category, attachment, and the tested assembly all govern. A shape is not a rating, an mph number in marketing is not a code determination, and neither this page nor a roof plan can make a wind-design determination for a building. That is a design professional's work, confirmed with the authority having jurisdiction.- Moisture and ventilation
This is the hip roof’s genuine weak point and it is almost always underestimated. IIBEC puts it flatly: “A frequent problem with hip roofs is that the ridge is either short or doesn’t really exist.” The attic below is the same size; the exhaust route at the top of it is not. The worked example further down does the arithmetic.
The compensating advantage is real and worth naming: 136 lineal feet of eave against 80 means substantially more soffit line available for intake. Hip roofs have an easier intake problem and a harder exhaust problem.
There is no universal ventilation ratio and no universal answer. Requirements depend on the adopted code edition, local amendments, climate zone, and the assembly itself, and a correctly designed unvented attic is an equally legitimate approach that needs no ridge at all. IIBEC notes that since the 2009 IRC an attic can be designed vented or unvented — it is a design decision, not a foregone conclusion.- Structural weight
Converting an existing gable roof to a hip is not a re-roof. It changes the framing, the load paths, the ceiling plane, and usually the wall top plates. Adding hip and jack rafters to an existing structure, or removing a gable end wall that is doing bracing work, are structural decisions.
This page explains the concept only. Any change to roof framing or to a gable end wall is designed by a licensed design professional for this specific building and permitted through the authority having jurisdiction. Nothing here is a structural determination.- Code and jurisdiction
Attic ventilation requirements come from the residential code your jurisdiction has adopted. The model provision sets a base net free ventilating area of 1/150 of the vented space, with an exception permitting 1/300 where two conditions are both met: not less than 40 percent and not more than 50 percent of the required area is provided by ventilators in the upper portion, no more than 3 feet below the ridge; and, in Climate Zones 6, 7 and 8 specifically, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling. The vapor-retarder condition attaches to those cold zones; the 40–50 percent condition attaches everywhere the exception is used. NRCA describes the same 1:150 base and 40–50 percent upper share as common to both the residential and building codes.
That is MODEL code language, reproduced here from the adopted Colorado residential code text and confirmed independently by NRCA (2018), IIBEC (2019), and DOE's Building America Solution Center. It has no jurisdiction of its own. Which edition your building department has adopted, what it amended, when it took effect, and how it is enforced on a re-roof permit are questions only that department can answer. Confirm before designing anything to these numbers.- Slope and drainage
A hip roof has no valleys unless wings or dormers are added, and it drains outward on all four sides — BASC lists “eaves and gutters all the way around for better drainage” as an advantage. The cost of that is 70 percent more gutter to buy, hang, and clean. Pitch also gates the hip venting solution: one vent manufacturer publishes a 5:12 minimum overall roof pitch for hip applications of its ridge vents.
- Maintenance
96 lineal feet of cap is 96 lineal feet of accessory to inspect and, eventually, to replace. Cap sits proud of the roof plane on an edge, which is where uplift is highest; it is fastened piece by piece; and it is the element most likely to need attention first. The inspection guide covers what a real inspection of it looks like.
- Insurance and mitigation credits
Some jurisdictions have built roof shape into insurance regulation explicitly. Florida is the clearest case. Section 627.0629(1) of the 2026 Florida Statutes requires that a rate filing for residential property insurance “must include actuarially reasonable discounts, credits, or other rate differentials, or appropriate reductions in deductibles, for properties on which fixtures or construction techniques demonstrated to reduce the amount of loss in a windstorm have been installed or implemented.”
The verification runs through the Uniform Mitigation Verification Inspection Form, OIR-B1-1802 (Rev. 04/26), adopted by Rule 69O-170.0155, Florida Administrative Code and effective 1 April 2026. Question 7 on that form is Roof Geometry, and the hip option is defined precisely: “Hip Roof: Hip roof with no other roof shapes greater than 10% of the total roof system perimeter.” The inspector records total length of non-hip features and total roof system perimeter. Porch and carport roofs attached only to the fascia or wall over unenclosed space are excluded from the calculation.
So a small gable dormer or a bay-window gable can push a roof over that 10 percent line and out of the classification. That is a real design consequence of a real rule, and it is worth knowing before a plan is drawn.
This describes a Florida regulatory mechanism as it stands on the adopted form, nothing more. It is not a promise of a discount, an amount, or eligibility, for any policy anywhere — including in Florida, where the credit that results is set by each insurer's filed rates. Nothing about this rule transfers to another state. Insurance outcomes are between a reader, their insurer, and the law where they live.
Cap, ventilation, and the two documents that interactSection link
A hip roof puts 2.4 times as much of the finished roof into an accessory product, and it puts the ventilation design under more pressure. Both are places where warranty language tends to have something to say.
- Hip and ridge cap is usually a separate product
Cap is manufactured, sold, and warranted separately from the field shingle. On a hip roof that separate product covers 96 lineal feet rather than 40, so more of the roof’s weather-facing surface sits under whatever terms the cap carries. Some system warranties require the manufacturer’s own cap rather than field shingles cut down; the glossary entry for hip and ridge cap notes that cutting field shingles into cap is common and is not always permitted by the product’s instructions. Read the actual instructions for the actual product being installed.
- Wind-speed coverage is conditional
Where a covering carries a stated wind-speed figure in a limited warranty, that figure is normally conditioned on installation strictly per the manufacturer’s instructions — fastener type, count, and placement, and often the direction cap is laid relative to prevailing wind. On a hip roof there are four hips on which that direction has to be decided. The warranty guide covers how these documents are structured.
- Ventilation clauses
Manufacturers commonly have something to say about attic ventilation in their warranty terms. On a hip roof, where the ridge cannot carry the exhaust on its own, this is the clause most likely to be tested. Get the proposed total net free area, the intake figure, and the exhaust figure in writing before the roof is closed — not because this page can tell you what any warranty requires, but because that is the evidence anyone would later ask for.
Repairability
Field shingle repair on a hip roof is ordinary. Cap repair is ordinary too, until the cap has aged: a replacement run against weathered cap shows, and there is 96 lineal feet of it in plain sight from the ground on all four elevations.
The harder repair is a ventilation retrofit. Cutting exhaust slots along hips on a finished roof means removing cap, cutting sheathing beside a structural hip rafter, and re-capping — more expensive and more disruptive than getting the design right when the roof is open. This is the argument for settling exhaust before the tear-off, not after the first summer.
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
Five of these are arithmetic questions with checkable answers. An installer who cannot produce the numbers has not done the takeoff.
How many lineal feet of ridge does this roof actually have, and how many lineal feet of hip?
On a simple rectangular hip, ridge is the long dimension minus the short one and each hip is a fixed length from the pitch. A competent estimator has these numbers because the cap order depends on them. A shrug here means the cap quantity is a guess, and so is the exhaust ventilation.
What exhaust product are you using, what is its published net free area per lineal foot, and what total does that give on my ridge?
Net free area is product-specific and published by the manufacturer. Multiply it by the ridge length and you have the exhaust the ridge can supply. If the answer is well short of the requirement, the next question answers itself.
How are you making up the exhaust shortfall, and are you mixing exhaust types to do it?
IIBEC warns that installing static exhaust vents on a roof that also has a ridge vent “should be avoided, because the static exhaust vents create a ‘short circuit’ of the intended air flow.” The right answer is one exhaust type sized to do the whole job — hip vents along the hips, or another single strategy — not a ridge vent plus a scatter of box vents.
What is the intake net free area, and is it at least equal to the exhaust?
One vent manufacturer states it without qualification: there must be at least an equal amount of soffit ventilation to balance the airflow, and never less. A hip roof has 70 percent more soffit line than the equivalent gable, so there is rarely an excuse for getting this half wrong.
Which hip and ridge cap product, and does the field shingle’s warranty require that specific cap?
Cap is a separate product covering 96 lineal feet of this roof. Cutting field shingles down to make cap is common and is not always permitted. The answer should name a product, not a method.
What waste allowance did you use, and how did you arrive at it for this roof?
A hip roof has 84 lineal feet of angled cut line that a gable does not. A higher allowance than a simple gable is legitimate and expected. An allowance the estimator cannot explain is a number they copied.
If any existing gable or roof vents are being left in place, why?
Leaving a gable vent open alongside a new ridge or hip vent is the classic mixed-exhaust short circuit. There are cases for keeping one; “we always leave them” is not one of them.
Require these in writing
- Lineal feet of ridge, hip, rake and eave, stated separately
- Hip and ridge cap: product name and total lineal feet
- Exhaust: product name, published net free area per lineal foot, lineal feet installed, and resulting total in square inches
- Intake: product name, published net free area, and resulting total in square inches
- The ventilation ratio being designed to, and which code route it follows
- Waste allowance as a percentage, and the roof surface area it is applied to
- Which existing vents are being closed and which are being retained
- Fastener type, count per cap piece, and the direction cap is laid on each hip
Misconceptions and failure modesSection link
Common misconceptions
Common belief
A hip roof is a hurricane-proof roof.
What is actually true
No roof is. The evidence supports a reduction in peak wind-induced pressure of as much as 50 percent in wind-tunnel testing, and the removal of a gable end wall that FEMA’s 2010 wind retrofit guide described as particularly vulnerable. Those are meaningful advantages and they are not immunity. Roofs come off in high wind at the sheathing fasteners, the roof-to-wall connection, the edge metal, and through opening failures that pressurise the building from inside. FEMA’s retrofit guidance is aimed at exactly those items, on both roof shapes.
Common belief
A hip roof costs more because there is more roof.
What is actually true
There is not. Over the same footprint at the same pitch the surface area is identical — 1,252 sq ft on the worked geometry, both ways, because both are plan area times the same pitch factor. The premium is framing complexity, 2.4 times the cap, and 84 lineal feet of angled cut line. If a proposal shows more squares for the hip option on the same house, ask why.
Common belief
A hip roof gets you an insurance discount.
What is actually true
In Florida there is a defined regulatory pathway: state law requires rate filings to include actuarially reasonable discounts for construction techniques demonstrated to reduce windstorm loss, and the adopted inspection form has a written definition of a hip roof — no other roof shape greater than 10 percent of the total roof system perimeter. That definition is strict enough that a modest gable dormer can disqualify a roof. Outside that framework, whether any credit exists is a matter of an individual insurer’s filed rates and the law of that state. This page cannot tell you whether you will receive one, or how much.
Common belief
You cannot properly ventilate a hip roof.
What is actually true
You can, but not with a ridge vent alone and not by accident. IIBEC identifies hip-specific ridge products designed to run along the hip lines and address the weather-infiltration problem that made the practice inadvisable with ordinary ridge vent, and notes powered options as another route. The failure mode is not that hip roofs cannot be vented — it is that a 12-foot ridge vent gets installed, the box is ticked, and nobody does the arithmetic.
Common belief
More ventilation is always better, so just add vents.
What is actually true
No. Under the model code route that permits the 1/300 ratio, the upper-portion share is bounded on both sides — not less than 40 percent and not more than 50 percent. Adding a scatter of box vents to a roof that already has a ridge vent creates the short circuit IIBEC warns about, where the upper vents feed each other instead of drawing from the soffits. And a correctly designed unvented attic assembly is a legitimate alternative that needs none of this. The ventilation guide works through both approaches.
Common belief
Hip roofs have no valleys, so they leak less.
What is actually true
A simple rectangular hip has no valleys, which is a genuine advantage. Most real houses are not simple rectangles. The moment a wing, an L, or a dormer is added, valleys appear — and on a hip roof they meet hips at intersections that are among the fussier details in residential roofing. Complex roof geometry is where that cost lives.
How it actually fails
- Under-vented attic, ridge vent installed and called done
- A ridge vent is run along the entire available ridge, which on a hip roof may be a small fraction of what the attic needs, and no further exhaust is provided. The attic runs hot and, in cold weather, humid.What you can see: From the ground: a ridge vent noticeably shorter than the building. On paper: a proposal that names a ridge vent but states no net free area total. This is checkable before anyone climbs anything.
- Mixed-exhaust short circuit
- Box vents or gable vents are added to make up the shortfall on a roof that also has ridge or hip vents. IIBEC warns this “should be avoided, because the static exhaust vents create a ‘short circuit’ of the intended air flow” — the high vents draw from each other rather than pulling air from the soffits.What you can see: Two or more different exhaust types visible on the same roof plane or the same attic space, particularly a ridge vent plus open gable-end louvres.
- Hip and ridge cap blow-off
- Cap sits on the highest, most exposed line on the roof and is fastened piece by piece. A hip roof has 2.4 times as much of it as the equivalent gable, so there is simply more of the roof depending on an accessory installed to a specific nailing pattern.What you can see: Lifted, displaced, or missing cap pieces along a hip after a wind event, often before any field shingle has moved.
- Hip vent slot cut wrong
- Exhaust slots along a hip are cut in sheathing that runs up to a structural hip rafter. A slot cut too wide, or cut into the rafter, is both a structural problem and a water problem, and it is buried under cap where nobody sees it.What you can see: Not visible after installation, which is the point. It is prevented by specification and by a contractor who has done it before — ask to see one.
- Gable-to-hip conversion done as a roofing job
- A gable end is removed and hip framing added without structural design, on the assumption that a roof shape change is roofing work. Gable end walls and their bracing participate in the building’s lateral system.What you can see: On a document rather than a roof: a proposal for a shape change with no engineer named and no structural permit referenced.
Sources and further readingSection link
Understanding Roofing / Published
Scope and limitations
- It cannot tell you whether a hip roof is the right shape for your building.
- Governing hazard, footprint proportions, attic plans, solar plans, and local labour costs all move that answer, and none of them are visible from here.
- It makes no wind-design determination.
- Wind loads on a real building are calculated by a design professional from site and building specifics; a shape is one input among many.
- It makes no structural determination.
- Changing a roof's shape, or removing a gable end wall, is engineered work for this building and is permitted through your authority having jurisdiction.
- It publishes no price.
- The hip premium is mostly labour hours, and no defensible national percentage or dollar figure was found to support one; the quantity takeoff is offered instead.
- The code ratios described here are model provisions read in an adopted state code and confirmed by trade and government sources.
- They are not the law where you live until your jurisdiction adopts them, and adoptions are amended.
- It cannot tell you whether you will receive an insurance credit, or how large one would be.
- It describes one state's regulatory mechanism and the written definition that mechanism uses.
- The worked geometry is a plain rectangle.
- Real houses have wings, dormers, chimneys, and unequal pitches, all of which change the numbers — though not the direction they move in.
- The wording quoted from FEMA P-804 comes from the 2010 first edition, which the 2023 second edition replaces.
- The second edition's own text could not be retrieved for direct reading, so no section, figure, or dimension is cited from it here — only what FEMA's own published overview of it states.
Hip Roof vs Gable Roof
U.S. Department of Energy — Building America Solution Center (Pacific Northwest National Laboratory)
That wind-tunnel testing by Meecham (1992) and Shao et al. (2018) found peak wind-induced pressures can be as much as 50% lower in a hip roof versus a gable roof; that hip roofs perform better in high winds and extreme weather while gable roofs are prone to damage from uplift and racking; that hip roofs are comparatively more complicated to design and build and more expensive than gable roofs; that hip roofs offer less attic storage space due to slopes on all sides and reduced space for solar PV panels; that hip roofs have eaves and gutters all the way around for better drainage; and that gable roofs offer lots of attic storage and are easier to make into additional living space.
A comparison guide, not a design standard or a code. Its 50% figure is a summary of two wind-tunnel studies, which are shape studies and not statements about any particular building. Its insurance-savings range traces to a 2013 estimate by an insurance broker and is not republished on this page for that reason.
Wind Retrofit Guide for Residential Buildings (FEMA P-804), first edition
Federal Emergency Management Agency — read on the Whole Building Design Guide (National Institute of Building Sciences) mirror / First edition, December 2010
The verbatim first-edition wording quoted on this page: that gable end walls are particularly vulnerable to damage in high-wind events due to their structural configuration, and that loads created by high winds can quickly overwhelm the capacity of gable end walls that do not have adequate structural connections (Section 4.1.4); that gable ends four feet or more tall should be braced as part of the Intermediate Mitigation Package, using retrofit studs, horizontal braces top and bottom transferring lateral load to the roof and ceiling diaphragms, strap connections between them, and metal brackets to the wall below (Section 4.2.2); and that enhanced sheathing-fastening applies to four-foot end zones on gable and hip roofs alike (Figure 4-3).
SUPERSEDED. FEMA published a second edition of P-804 in 2023; every quotation, section number, and figure number attributed to this document on this page belongs to the 2010 first edition and is labelled as such, and none of them should be read as the numbering of the current guide. It was never adopted law and is not a wind-design method for a specific building; FEMA's own disclaimer states that opinions and recommendations in it do not necessarily reflect FEMA's views. fema.gov blocks automated retrieval, so the copy read for this page was the PDF served by the Whole Building Design Guide, whose cover carries the FEMA P-804 / December 2010 imprint.
FEMA Advisory: Overview of FEMA P-804 (2023), Wind Retrofit Guide for Residential Buildings in Hurricane-Prone Regions
Federal Emergency Management Agency, Building Science / July 2023
That FEMA released a second edition of P-804 in 2023 replacing the 2010 guide; that the second edition organises work into Basic, Intermediate and Advanced Mitigation Packages which should be implemented cumulatively beginning with the Basic package; that the Basic package covers sealing and strengthening the roof deck, inspecting and improving deck attachment, eave underlayment details, wind-resistant roof coverings, and the water intrusion resistance of attic vents; and that 'strengthening gable end walls' sits in the Intermediate package alongside windborne debris protection of windows, doors and garage doors, soffit strengthening, chimney attachment, and strengthening connections of attached structures, with a continuous load path in the Advanced package.
FEMA's six-page overview of the Guide, not the Guide itself: it contains no bracing dimensions, member sizes, or fastener schedules. It is guidance and grant-programme framing, not adopted law, and it makes no determination for any specific building. fema.gov blocks automated retrieval; the copy read for this page was the identical PDF served by the Homeland Security Digital Library (hsdl.org, docid 880866), and the FEMA URL above is the authoritative location. The second edition's own chapter and figure numbering was not readable for this page, which is why no section number from it is cited here.
Section 627.0629(1), Florida Statutes — Residential property insurance; rate filings
The Florida Legislature / 2026 Florida Statutes
That a rate filing for residential property insurance in Florida must include actuarially reasonable discounts, credits, or other rate differentials, or appropriate reductions in deductibles, for properties on which fixtures or construction techniques demonstrated to reduce the amount of loss in a windstorm have been installed or implemented.
Florida law only. It creates a filing requirement on insurers; it does not set an amount, guarantee eligibility, or apply anywhere outside Florida. Nothing in it promises any reader a discount.
Uniform Mitigation Verification Inspection Form, OIR-B1-1802 (Rev. 04/26), adopted by Rule 69O-170.0155, F.A.C.
Florida Office of Insurance Regulation / Revision 04/26
The verbatim wording of Question 7, Roof Geometry — that answer A is 'Hip Roof: Hip roof with no other roof shapes greater than 10% of the total roof system perimeter'; that the inspector records total length of non-hip features and total roof system perimeter; and that roofs of porches or carports attached only to the fascia or wall of the host structure over unenclosed space are not considered in determining roof perimeter or roof area for roof geometry classification.
A Florida form adopted by Florida rule. It classifies a roof; it does not set a credit. The revision code 04/26 is printed on every page of the form; the 1 April 2026 effective date is not printed on the form itself and was confirmed separately against the Florida Administrative Register entry for Rule 69O-170.0155 (flrules.org/gateway/ruleNo.asp?id=69O-170.0155), which records that effective date. This revision supersedes an earlier one that numbered the same question 5 rather than 7. Verify the current revision before relying on any wording here.
Attic Ventilation 101
IIBEC (International Institute of Building Enclosure Consultants) — Joan P. Crowe, AIA / 1 November 2019
That 'a frequent problem with hip roofs is that the ridge is either short or doesn't really exist'; that hip ridge vents can be installed along the ridge lines of a hip roof and that hip-specific ridge products are available, designed to address weather infiltration; that installing static exhaust vents on a roof that also has a ridge vent 'should be avoided, because the static exhaust vents create a short circuit of the intended air flow'; that approximately equal amounts of ventilation should be placed at the soffit or eave level and at or near the top of the attic, with intake always equal to or greater than exhaust; the 1:150 base ratio and the 1:300 exception with its Climate Zone 6-8 vapor retarder condition and its 40-50 percent upper-portion condition within 3 feet of the ridge; and that since the 2009 IRC an attic can be designed vented or unvented, making it a design choice rather than a code mandate.
Trade technical guidance written in 2019. Its code descriptions reflect the editions current then and are not a substitute for the code your jurisdiction has adopted. Note the authorship: the article appears in IIBEC's publication, but its author is identified there as a codes and regulatory compliance manager at a roofing manufacturer, so it is not a wholly disinterested account of ventilation products. The claims taken from it here are either descriptions of the code text — independently confirmed against NRCA and DOE BASC below — or statements about hip geometry that do not favour any product.
Clearing the air
Professional Roofing (National Roofing Contractors Association) — Mark S. Graham / July 2018
That both the residential and building codes require the net free ventilating area to be at least a 1:150 ratio of the space being vented; that the exception requires at least 40 percent and not more than 50 percent of the NFVA in the attic's upper portion; and that for large-volume attics, such as where the roof slope is greater than 8:12, designers should consider increasing the amount of ventilation.
An independent confirmation of the ratio language, written in 2018. NRCA is a contractor trade association, not a code authority, and the article is not a jurisdiction-specific determination.
Calculating Attic Passive Ventilation
U.S. Department of Energy — Building America Solution Center (Pacific Northwest National Laboratory)
The calculation method reproduced in this page's worked example — attic area divided by the ratio, converted to square inches at 144 in² per ft²; that net free ventilation area is the clear open area of a vent accounting for screening restrictions; that no more than 50 percent and no less than 40 percent of the required area should be located high on the roof; and that upper vents must be at least 3 feet above the soffit or eave vent openings and no more than 3 feet below the highest point of the roof.
A calculation guide. Its worked example uses a different house than this page's, and it makes no mention of hip roofs or of ridge length — the hip-versus-gable comparison in the table below is this page's own arithmetic applied to BASC's method.
Residential Code 2021 (Colorado DFPC adoption), Section R806.2 — Minimum vent area
UpCodes — a commercial code aggregator, not an adopting jurisdiction / 2021 edition as adopted by the Colorado Division of Fire Prevention and Control
The verbatim wording read for this page: 'The minimum net free ventilating area shall be 1/150 of the area of the vented space,' with the exception permitting 1/300 'provided both of the following conditions are met' — a Class I or II vapor retarder installed on the warm-in-winter side of the ceiling in Climate Zones 6, 7 and 8, and not less than 40 percent and not more than 50 percent of the required ventilating area provided by ventilators located in the upper portion of the attic or rafter space, not more than 3 feet below the ridge.
A commercial aggregator, cited only for wording that was actually read on the page, and nothing more. It is not adopted law anywhere except Colorado, it is a 2021 rather than a 2024 edition, and it is not evidence of what any other jurisdiction has adopted. It is included here because the ICC's own hosted text could not be retrieved for direct reading; the substance was independently confirmed by NRCA (2018), IIBEC (2019), and DOE BASC above. Confirm the adopted edition, its amendments, and its effective date with your authority having jurisdiction.
Ventilation FAQs and product net free vent areas
Cor-A-Vent, Inc. — manufacturer
Product-specific published net free vent areas used in this page's worked example: V-600 at 20 square inches per lineal foot, V-300 at 13.5 square inches per lineal foot, and Revolution at 12 square inches per lineal foot; that for hip applications the overall roof pitch must be at least 5:12 and caulking under the vent is recommended; and that a ridge vent must have at least an equal amount of soffit ventilation to balance the airflow, never less.
Manufacturer product data, specific to these products. Net free area varies by product and by manufacturer; the 13.5 sq in per lineal foot used in the worked example is one product's published figure chosen as a mid-range illustration, not a standard value and not a recommendation of this product. Use the published figure for the product actually being installed.