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
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