Gambrel
A change in pitch on each side creates a distinct transition to inspect and specify.
Roof types
A roof is a system, not a surface.
Learn the shape, slope, covering, layers, edges, drainage, and building conditions that make one roof work differently from another.
30-second answer
How do I choose the right roof type?
Start with the building and the roof’s slope—not a material brochure. A good choice must fit drainage, structure, climate, access, maintenance, ownership horizon, and budget as one system.
Geometry first
Slope decides how much roof you are buying.
Two buildings with the same footprint do not buy the same roof. Before any material comparison, pitch sets the surface area that every quantity, every allowance, and every price is calculated from.
| Pitch | Surface multiplier | Roof surface | Roofing squares |
|---|---|---|---|
| 2:12 | ×1.0138 | 1,825 sq ft | 18.2 |
| 3:12 | ×1.0308 | 1,855 sq ft | 18.6 |
| 4:12 | ×1.0541 | 1,897 sq ft | 19.0 |
| 5:12 | ×1.0833 | 1,950 sq ft | 19.5 |
| 6:12 | ×1.118 | 2,012 sq ft | 20.1 |
| 7:12 | ×1.1577 | 2,084 sq ft | 20.8 |
| 8:12 | ×1.2019 | 2,163 sq ft | 21.6 |
| 9:12 | ×1.25 | 2,250 sq ft | 22.5 |
| 10:12 | ×1.3017 | 2,343 sq ft | 23.4 |
| 11:12 | ×1.3566 | 2,442 sq ft | 24.4 |
| 12:12 | ×1.4142 | 2,546 sq ft | 25.5 |
That is geometry, not a takeoff. Measure the plan area to the edge of the eaves—overhangs are part of the footprint you start from, which is what the estimator asks for. What the multiplier cannot do is account for dormers, a second pitch, parapets, porches, or separate structures; a real quantity is measured plane by plane.
Identify the shape
Start with the roof you have.
A roof shape describes geometry. The guides explain its drainage paths, transitions, and the questions it raises for a roofing project.
Gable roofs
Two principal sloping planes meeting at a ridge: identify the shape and its project considerations.
Hip roofs
Slopes on every side, with hips, ridges, and accessory quantities to account for.
Shed roofs
A single principal roof plane and the wall and edge transitions it creates.
Flat and low-slope roofs
Why drainage and the complete waterproofing assembly lead this decision.
Other shapes and combinations
Identify the details that add complexity.
Follow the shape that matches your building, then use pitch and material guidance to evaluate the system.
Mansard
Read about steep lower slopes, upper roof sections, and their transitions.
Butterfly
Inward-facing slopes make the central drainage arrangement a key question.
Combination
Identify where different shapes and slopes meet on one building.
Complex geometry
Translate valleys, dormers, and transitions into measurement and scope questions.
Materials for the shape
Use slope, structure, exposure, and project priorities to build a material shortlist.
Next step
Turn a material shortlist into a buying plan.
The buying kit’s quote checklist is published as an ungated preview. Use it to make every installer define the same scope against the system you chose.
Preview the buying kit