Flat Roof Slope Requirements

Quick roofing guide to the international building code.

Flat roof slope requirements.

In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. First off lets get some terminology out of the way. There are two types of flat roof. To put it in perspective the angle of this slope would be around 30 degrees.

They provide excellent weather resistance great value and now more than ever a tremendous range of beautiful designs and color blends. The steeper the roof slope the less potential for water to backup however the roofing materials established in chapter 9 must meet to minimum slope requirements. Roof slope equivalents as rise. The profile is the shape taken by the sheets when you bend them to form panels.

Roof pitch multiplier table. Proper roof slope can be an important consideration when designing high performance roof systems. Following is a review of code requirements and nrca s roof slope guidelines as well as some additional factors designers should consider. The minimum slope of a roof depends on the roof s profile.

Express the slope of a metal roof by a ratio which indicates the pitch of the roof. However you can only use this pitch with built up roofing or specialized synthetic roofing. The slope of a roof or pitch is determined by how many inches the roof rises over 1 foot or 12 inches. Minimum and maximum roof slope limits vary based on specific roof system and project types.

Complete list of roofing types. You need to consider the slope requirements of each panel to determine this minimum slope. Run in degrees and as percentage the minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. Since they vary in quality as well as method of installation the choice preferred for a flat roof will ultimately have an effect on the final slope of the flat roof.

Cold roofs and warm roofs. Asphalt shingles continue to be the most widely installed roof covering option in north america. Degrees to pitch rise in run table. All of these codes are produced by the international code council icc.

Iecc is of particular importance to low slope roof design due to its r value requirements which affect the amount of insulation that has to be included in roof assemblies. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. This means that the rise of the slope goes up or down 8 inches for every 12 inches. In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay.

The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run. Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling.