Minimum Required Roof Pitch for All Roofing Materials
Roof Online Staff
Updated June 2, 2021
Scroll down to see the chart.
General Minimum Roof Pitch Standards
The minimum roof slope allowed by code for any type of roof is ⅛-in-12, 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.
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.
Recommended Minimum Roof Slope
Specific roofing products may have different recommended minimum slopes; 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 void the warranty.
This is particularly important to pay attention to when using metal roofing products, such as standing seam metal, which have a multitude of profiles, attachment methods, and seam/lap/joint styles which can affect the recommended slope.
The manufacturer’s minimum recommended slope or pitch will sometimes be steeper than the minimum that is required by code for a particular roofing material.
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).
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.
Steeper roofs shed water and snow faster and are less likely to have debris accumulate on the roof. They also tend to have less exposure to the sun’s UV rays than roofs that are less steep.
Minimum Roof Pitch Table
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.
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.