Auralex StopGap Acoustical Sealant

The weakest point in any soundproofed wall is never the wall itself — it's the gaps. Electrical box cutouts, perimeter seams where walls meet floors and ceilings, pipe penetrations, and construction gaps all act as acoustic leaks that compromise the STC rating of an otherwise well-built wall system. A wall rated STC 50 with an unsealed gap at the baseboard can perform like STC 35 in practice. StopGap is designed specifically to seal these transmission paths.

Why Standard Caulk Doesn't Work

Standard construction caulk hardens over time and cracks as buildings settle and walls flex. Once it cracks the acoustic seal is broken — often without any visible sign of failure. StopGap is formulated to remain highly elastic for up to five times longer than standard caulk alternatives, maintaining a flexible, pliable seal that moves with the structure rather than cracking against it. The acoustic seal stays intact long after standard caulk would have failed.

Application

StopGap is water-based — easy to apply, minimal mess, no residual run-off. It is paintable and non-staining, allowing a clean finished appearance after installation. The sealant meets ASTM C-834 standards for flame retardancy.

Comes in a 29 oz cartridge — larger than standard caulk tubes, requiring a larger-than-standard caulking gun available at any hardware store. One cartridge covers approximately 89 linear feet at a 3/8" bead width.

Specifications:

Format: 29 oz caulking cartridge
Coverage: Approximately 89 linear feet at 3/8" bead
Composition: Water-based, highly elastic
Fire rating: ASTM C-834 flame retardant
Finish: Paintable, non-staining
Requires: Large-format caulking gun (not included)

Applications: Perimeter seams in wall systems, electrical box cutouts, pipe penetrations, construction gaps, and any acoustic isolation project where air gap sealing is required to achieve specified STC ratings.