Residential Building Inspector B1Footings and FoundationsMedium
A residential building inspection reveals that the foundation drain for a newly constructed home is installed with a solid pipe, and the aggregate cover over the drain is less than 6 inches (152 mm). The surrounding soil is fine-grained. According to the 2021 IRC, what is the primary deficiency with this installation?
- AA filter membrane should be installed over the aggregate.
- BThe solid pipe should be replaced with a perforated pipe.
- CThe aggregate cover over the drain should be at least 6 inches.
- DThe foundation drain should be connected to a storm sewer.
Show answer & explanationAnswer & explanation
Correct answer: B. The solid pipe should be replaced with a perforated pipe.
IRC Section R405.1 requires foundation drains to be placed around the perimeter of a foundation and consist of a perforated pipe. A solid pipe would not effectively collect subsurface water. While other options might be good practices, the use of a solid pipe is a fundamental deficiency for a foundation drain.
Why the other options are wrong
- A. A filter membrane (geotextile fabric) is required over the aggregate when fine-grained soils are present, which is a deficiency, but not the primary one given a solid pipe cannot drain.
- C. IRC R405.1 states the drain shall be covered with not less than 6 inches of gravel or crushed stone, making the deficient cover a valid point, but the pipe type is a more fundamental error for a 'drain'.
- D. Connecting to a storm sewer or approved discharge point is required, but the method of drainage collection (perforated pipe) is a more primary issue than the discharge point in this context.
Foundation Drain Pipe Type
The type of pipe required for foundation drains to effectively collect and convey subsurface water.
- Must be perforated to allow water entry.
- Installed around the perimeter at or below the footing.
- Specified in IRC Section R405.1.
Memory trick: Drainage Needs Holes: Perforated is Key.