Determine whether a foundation wall requires dampproofing or full waterproofing under IRC/IBC

Steps

1. Identify which code governs: IRC Section R406 for residential (≤3 stories), IBC Section 1805 for commercial/other buildings.
2. Default rule (IRC R406.1): dampproof exterior foundation walls enclosing habitable/usable below-grade space from finished grade to the top of footing (or 6 in below top of basement floor) with an approved bituminous coating or equivalent — this is rated for ordinary soil moisture, not hydrostatic pressure.
3. Trigger for full waterproofing (IRC R406.2 / IBC 1805.3): a high water table, poorly-drained soils, or documented hydrostatic pressure at or above the exterior wall depth requires a system rated to resist hydrostatic head instead of dampproofing — confirm against the geotechnical report, not just a visual soil assessment.
4. IBC additionally treats sustained water-table contact (commonly a multi-month annual condition) as a waterproofing trigger — confirm this with the geotechnical engineer of record.
5. Check local amendments: jurisdictions with known high water tables (coastal, Gulf Coast, Great Lakes) frequently amend R406 to mandate waterproofing outright regardless of a case-by-case hydrostatic determination.