Proper site drainage is a crucial element in preventing foundation failures. Water should be directed away from a supporting foundation and off the site. The code is specific in this regard.

So how about roof drainage? Specifically, does the IRC prescribe gutters as a controlled method of roof drainage when a home is built on a slab-on-grade foundation? A close look at the code will answer this important question.

The International Residential Code addresses roof drainage in Section R801.3. The code reads as follows:

"In areas where expansive or collapsible soils are known to exist, all dwellings shall have a controlled method of water disposal from roofs that will collect and discharge all roof drainage to the ground surface at least 5' away from foundation walls or to an approved drainage system."

The IRC is sometimes misunderstood because it is not read in context. To understand the meaning of a code one must define its terms. Many read the above code reference and assume that the author refers to all types of foundation systems. However, this is not the case. The code specifically notes that water collected at the roof and discharged to the ground surface is required to be discharged at least 5' away from foundation walls only.

A foundation wall is typically utilized on crawl space or basement type construction. This type of foundation system is extremely susceptible to damage due the additional loads that can be imposed as a result of expansive soil. Discharging roof water away from foundation walls serves to minimize the saturation of expansive soils.

Section R801.3 of the IRC does not pertain to buildings constructed on slab-on-grade foundations. Therefore a guttering system is not required. However, this does not relieve the builder of the intent of the code which to direct water away from the building and off the lot. While gutters are not a code requirement, they very well may benefit the builder in certain circumstances in achieving positive site drainage.

Qualified Inspection Services provides third party residential inspection services designed to keep builders code compliant. To find out how our services may benefit your company, please contact us today.