Party Walls: Party Walls are Outside Walls

A follow-up to Party Walls: No Odour, No Noise, pictures are worth 1000 words.

1. Wrap the rims with header wrap. We know from experience that leakage around the rim joists will make or break an air test.
2. Caulk the header wrap onto the foundation wall with acoustical sealant. This completes the air-barrier in the basement.
3. Compartmentalize the party walls. Frame the inside walls separately from the party walls of adjoining garages or bump-outs.
4. Seal the ends with XPS or house wrap stopping cold air from entering between the party walls.
5. Air-seal one wall with poly and the adjacent wall with house wrap. We know that using drywall as an air barrier just doesn’t work that well.
6. Prep the party walls with poly or house wrap and drywall BEFORE installing stairs. Think of stairs and landings as back-framing.