Minimum Roof Pitch Required by Code • 33 Roof Types
Roof Online Staff, Updated June 2, 2021
Scroll down to see the chart.
Table of Contents
- Related Pages
- General Minimum Roof Pitch Standards
- Recommended Minimum Roof Slope
- Minimum Roof Slope and the Building Code
- About This Minimum Roof Slope Chart
- Table of Minimum Acceptable Roof Pitches
Related Pages
- Building Codes and Roofs
- Complete List of Roofing Types
- How Long Every Type of Roof Lasts
- Roof Pitch Multiplier Table
- Roof Pitch: 3 Ways of Expressing Roof Slope
- Roof Slope: Degrees to Pitch (Rise-in-Run) Table
General Minimum Roof Pitch Standards
The minimum roof slope allowed by code for any type of roof is ⅛-in-12 (0.60 degrees), applicable only to coal tar pitch roof systems.
All other flat roof materials require a minimum slope of ¼-in-12, which is why flat roofs are properly known as “low-slope” roofs.
Asphalt roof shingles have a minimum slope requirement of 2-in-12 with a double application of underlayment, and 4-in-12 otherwise. Most other pitched roofing materials, such as clay tile or metal panels, require minimum slopes from 2½-in-12 to 4-in-12.
Read on to learn more about roof slope requirements, or scroll to the end to see the chart with all the different roofing types.
Recommended Minimum Roof Slope
Even though building codes state the minimum slope allowed for a material in general, specific roofing products may have different recommended minimum slopes. You should always check the manufacturer’s product data sheets for the actual product you intend to use, and always follow the manufacturer’s installation instructions.
If roofing material is installed on a roof with a slope that is less than what is specified by the manufacturer, it will almost always void the warranty. You don’t want that!
The manufacturer’s slope recommendation should be considered a requirement for warranty purposes.
The manufacturer’s minimum slope recommendation is particularly important to pay attention to when using metal roofing products, such as standing seam metal roof systems. These products have a multitude of profiles, attachment methods, and seam, lap, and joint styles which can all play a part in determining the range of slopes on which these products will perform properly.
The manufacturer’s minimum recommended slope or pitch for a specific product will often be steeper than the minimum that is required by code for that general category of roofing material.
Steeper Roofs Perform Better
As a very general rule, a steeper roof will perform better and last longer than a roof with a lower slope.
A steeper roof will shed water and snow faster and more completely, and is less likely to have debris such as tree leaves accumulate on the roof. They also tend to have less exposure to the sun’s damaging UV rays over the course of a day than a less steep roof.
Minimum Roof Slope and the Building Code
For each type of roofing material, you can see the actual language used in the model 2018 International Building Code at the UpCodes website.
Click to see Section 1507 (Requirements for Roof Coverings).
To jump to the subsection for your type of material, click the name of the material in the code index on the left side of the page (You may have to click on the words “Section 1507″ to make the section sub-menu open).
For the actual language in the model 2018 International Residential Code, click to see Section R905 (Requirements for Roof Coverings).
About This Minimum Roof Slope Chart
The following table shows the minimum required (allowable) roof slope for each type of roofing material mentioned in the code.
The values given here (except for thatch) are taken from the model International Building Code, which forms the basis for almost every building code in the United States.
Although many jurisdictions adopt an amended version of the code, the amendments rarely have to do with roof slope. Still, there’s no guarantee that they won’t, so you should always check with your local code authority in case there are local amendments to the code that affect required minimum roof slopes.
Table of Minimum Acceptable Roof Pitches
If you need help figuring out the slope or pitch of your roof, we recommend this slope finder on Amazon. It’s very inexpensive and very accurate.
| Minimum Slope for Roofing Materials as required by the International Building Code or the International Residential Code |
||
|---|---|---|
| Roofing Material or System | Minimum Required Slope: Standard Pitch (X-in-12) |
Minimum Required Slope: Degree Equivalent |
| Asphalt Shingles | 4-in-12 | 18.43° |
| Asphalt Shingles With Special Underlayment Requirements |
2-in-12 | 9.46° |
| Built-Up Roof, Asphalt | ¼-in-12 (0.25-in-12) |
1.19° |
| Built-Up Roof, Coal Tar Pitch | ⅛-in-12 (0.125-in-12) |
0.60° |
| Clay Tile, Barrel, Mission or Two-Piece | 4-in-12 | 18.43° |
| Clay Tile, Barrel, Mission or Two-Piece With Special Underlayment Requirements |
2½-in-12 (2.5-in-12) |
11.77° |
| Clay Tile, Barrel, Spanish or S-Shaped | 4-in-12 | 18.43° |
| Clay Tile, Barrel, Spanish or S-Shaped With Special Underlayment Requirements |
2½-in-12 (2.5-in-12) |
11.77° |
| Clay Tile, Flat | 4-in-12 | 18.43° |
| Clay Tile, Flat With Special Underlayment Requirements |
2½-in-12 (2.5-in-12) |
11.77° |
| Concrete Tile, Barrel, Mission or Two-Piece | 4-in-12 | 18.43° |
| Concrete Tile, Barrel, Mission or Two-Piece With Special Underlayment Requirements |
2½-in-12 (2.5-in-12) |
11.77° |
| Concrete Tile, Barrel, Spanish or S-Shaped | 4-in-12 | 18.43° |
| Concrete Tile, Barrel, Spanish or S-Shaped With Special Underlayment Requirements |
2½-in-12 (2.5-in-12) |
11.77° |
| Concrete Tile, Flat | 4-in-12 | 18.43° |
| Concrete Tile, Flat With Special Underlayment Requirements |
2½-in-12 (2.5-in-12) |
11.77° |
| EPDM Membrane | ¼-in-12 (0.25-in-12) |
1.19° |
| Fiber Cement Shingles | 4-in-12 | 18.43° |
| Metal: Metal Roof Panels Non-soldered, No Lap Sealant |
3-in-12 | 14.04° |
| Metal: Metal Roof Panels With Lap Sealant |
½-in-12 (0.5-in-12) |
2.39° |
| Metal: Metal Roof Tiles (Metal Roof Shingles, Interlocking) |
3-in-12 | 14.04° |
| Metal: Standing Seam | ¼-in-12 (0.25-in-12) |
1.19° |
| Metal: Stone-Coated Steel (Metal Roof Shingles, Interlocking) |
3-in-12 | 14.04° |
| Modified Bitumen | ¼-in-12 (0.25-in-12) |
1.19° |
| PVC Membrane | ¼-in-12 (0.25-in-12) |
1.19° |
| Roll Roofing, Asphalt | 1-in-12 | 4.76° |
| Slate Roofing | 4-in-12 | 18.43° |
| Spray Polyurethane Foam | ¼-in-12 (0.25-in-12) |
1.19° |
| Synthetic Shingles/Slates/Tiles (“Composite”, Plastic) |
4-in-12 | 18.43° |
| Synthetic Shingles/Slates/Tiles (“Composite”, Plastic) With Special Underlayment Requirements |
3-in-12 | 14.04° |
| Thatch (see note below) |
12-in-12 | 45° |
| TPO Membrane | ¼-in-12 (0.25-in-12) |
1.19° |
| Wood (Cedar) Shakes | 4-in-12 | 18.43° |
| Wood (Cedar) Shingles | 3-in-12 | 14.04° |
Note: Thatched roofs are not mentioned in the International Building Code. The minimum slope given for thatch in the table is based on best practice standards prevalent in the thatching community.
