Air-seal tub and shower enclosures BEFORE drywall — prevents major air-leakage path
BASC Guide — guides/air-sealing-shower-and-tub-enclosuresDescription
Tub and shower enclosures often back up to exterior walls or attic spaces; the framing voids behind them are typically left unsealed (because the drywall doesn't extend behind them). Best practice: install rigid air barrier (½-in foil-faced foam, foam board, or rigid backerboard) on the framed wall BEHIND the tub/shower before the fixture is installed, sealed at all joints with foam/caulk. This converts a major air-leakage path into a continuous barrier.
Why this exists
Untaped/unsealed walls behind tubs are one of the highest air-leakage rates on a typical blower-door test (often 100+ cfm at 50 Pa from this single defect). Architects + builders forget this detail because the fix happens at a critical scheduling moment — between framing and fixture install. Call out the detail explicitly on the wall section.
Categories
Source
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Slab-on-grade vapor barrier + capillary break required · HUD RSDG §4.6
- Roof overhangs protect walls — 12-24 inches in humid climates; one foot per story below · HUD RSDG §5.6.5
- Bathroom walls must contain reinforcement to allow later installation of grab bars · HUD FHA Design Manual Requirement 6 (Chapter Six)
- Usable kitchens and bathrooms: 30x48 inch clear floor space at fixtures + 60 inch turn circle · HUD FHA Design Manual Requirement 7 (Chapter Seven)
- Toilet side grab-bar reinforcement: 36 inches from back wall, 33-36 inches above floor · HUD FHA Design Manual Chapter Six §6.4
Last reviewed 2026-05-15.