A common trend we are seeing in housing developments is the reduction of setbacks. Though setbacks are often regulated by the local jurisdiction’s zoning requirements, they impact the application of the building requirements found in the International Residential Code (IRC), the most commonly adopted code by jurisdictions to regulate the construction of one- and two-family dwellings and townhomes.
We often see the side yard setback being reduced to five feet in new developments. When this occurs, some contractors, to ensure correct placement, have the location of the footings or foundations verified by a surveyor. Some jurisdictions have written policies in place that require such verification when placement occurs within a minimum distance of the required setback.
There are a couple of issues that should be addressed on the plans for buildings, which are even more critical when built to five-foot setbacks. First, the setback dimension needs to account for the finish materials on the exterior walls and their projection beyond the foundation. Second, the projections on the exterior walls that are affected need to be compliant.
To establish requirements for such exterior walls and their projections, we need to review Table R302.1(1) for dwellings without sprinklers and Table R302.1(2) for dwellings with fire sprinklers. We will focus on the requirements in Table R302.1(1) for this discussion. If the setback dimension, measured at a right angle from the lot line to the face of the wall as stated in the definition of fire separation distance in Section 202, is less than five feet, then the wall must have a one-hour fire rating with exposure from both sides. If a projection of the wall, such as a soffit, is located less than five feet from the lot line, it must be protected as stated in Table R302.1(1). However, if the top of the wall is fire-blocked from the top of the wall to the bottom of the roof sheathing at an eave soffit, or if the gable end at the rake soffit does not contain a gable vent, then it complies with the footnotes of Table R302.1(1) and the underside of the soffit need not be protected. Please note that projections are prohibited from being closer than two feet to the lot line.
Hopefully, you find this information useful, or at least it provides some clarity on the subject.
References: This article is based on the 2021 edition of the International Residential Code as published by the International Code Council.
