The soils information for this lot classifies the ground as a well-drained gravel and sand mixture in Group I, the excavation has stayed dry through two weeks of weather, and no perforated pipe or drainage stone has been placed around the footing of the basement wall. What should the inspector conclude?
- AA drain is required, because every foundation wall enclosing a basement must have a perimeter drain regardless of the soil.
The requirement is not absolute; it is written with a soil-based exception.
- BA drain is required unless the basement is going to remain unfinished for the life of the building.
The trigger is a below-grade space that is habitable or usable, not whether the basement gets finished.
- CNo drain is required, because the exemption covers any lot where the excavation happens to be dry on the day of inspection.
A dry hole in fair weather is not a soil classification and cannot support the exemption.
- No drain is required, because the code exempts foundations resting on well-drained ground or on Group I sand and gravel soils.
Why D is correct
The drainage requirement carries an exception for foundations installed on well-drained ground or on sand-gravel mixture soils classified as Group I. With that classification in the soils information for the lot, the omission of drain tile is compliant, and the inspector documents the basis rather than writing a correction.
What this question is testing
Whether the candidate can apply an exception correctly, which means checking that the specific condition named in the code is documented rather than assumed from a field observation.
On the job
This one comes up constantly in sandy coastal and glacial-outwash subdivisions where builders have gone decades without drain tile and are genuinely puzzled by the question. The professional answer is to ask for the document that classifies the soil. If the file has it, the exemption stands and everybody moves on; if nobody can produce it, the drain goes in, because the cost of the pipe and stone is trivial next to the cost of proving the point later.
Memory technique
Group I gravel drains itself; clay needs a pipe.
Exam tip
Exceptions on the exam are usually keyed to a named classification or condition; look for that exact wording in the stem.
Where to look it up
IRC Chapter 4, the foundation drainage section at R405.1, including the exception at the end of the paragraph.