Site Grading


On IBC1804.4 Site Grading, I am confused when should we use 5% and when to use 2% slope.

Welcome to the ARE Community, @theresaninh69! Thanks for writing in.

According to this code section, the site grading must slope away from footings at 5% minimum slope for at least 10 feet. This prevents ponding of water against the footings. As an alternative, swales may be used and sloped at 2% minimum where located within 10 feet of the building foundation.

Per exception #1, a minimum 2% slope may be allowed in certain climatic/soil conditions.

Check out Building Codes Illustrated (page 378) for a great visual of this. While this resource is not specifically an NCARB-recommended resource, I found it very helpful to visualize various code requirements.

Hope this helps!

Kiara Galicinao, AIA, NCARB
Black Spectacles