A concrete foundation encloses usable below-grade space. The documented bearing ground is a well-drained sand-gravel mixture classified as Group I under 2021 IRC Table R405.1. Considering R405.1’s soil exception, is a foundation drainage system required by that section?
- AYes, with no soil exception
- BYes, unless the basement remains unfinished forever
- CNo, because a temporarily dry excavation alone is sufficient
- No; the stated soil condition satisfies the section’s drainage exception
Where to look it up
https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042182/2021_International_Residential_Code.pdf
Why D is correct
R405.1 generally requires drainage around concrete or masonry foundations retaining earth and enclosing below-grade habitable or usable space. Its exception covers the stated well-drained ground or Group I sand-gravel condition. Classification and actual ground conditions, rather than a few days of dry weather, support the finding here. This conclusion is limited to R405.1 and does not waive unrelated site drainage, waterproofing or locally adopted requirements. See printed p.4-42. Source: https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042182/2021_International_Residential_Code.pdf