StopGap™ Acoustical Sealant — 29 oz
The cheapest part of a soundproofing build, and the one that decides whether the rest of it worked.
A water-based, permanently flexible acoustical sealant for the perimeter of wall systems and around electrical cutouts. One 29 oz tube covers roughly 32 linear feet at a 3/8" bead. Sold singly or by the case of 12.
What this fixes
Sound leaks through gaps. You can build a wall with mass barrier, resilient clips, and double drywall, and then lose most of the benefit through an unsealed perimeter joint or an outlet cutout — because air paths carry sound almost perfectly.
Sealing those gaps is what turns a pile of soundproofing materials into an actual assembly. Applied per ASTM C-919 — two beads at the top, bottom, and all perimeter edges — StopGap contributes to achieving an STC of 53.
Where it goes
| Location | Why |
|---|---|
| Wall perimeter — top, bottom, both edges | The main event. Two continuous beads where drywall meets floor, ceiling, and adjacent walls. |
| Around electrical box cutouts | Outlets and switches are direct holes through your wall assembly. Sealing them is how you hold your specified STC/MTC values. |
| Seams and penetrations | Anywhere a pipe, wire, or duct passes through the assembly. |
Why acoustical sealant, not regular caulk
Standard caulk cures hard and eventually cracks as the building moves — and a cracked seal is an open air path again. StopGap dries to a tough surface film but stays pliable underneath, and stays flexible up to five times longer than alternative brands.
It's also paintable, dries white, non-staining, has no residual run-off, and meets ASTM E-84 for flame retardancy.
Before you order
You will need a larger caulking gun than the one in your garage. StopGap comes in a 29 oz tube, which does not fit a standard 10 oz gun. Pick up a 29 oz–capacity gun at any hardware store before install day.
Estimate quantity from linear feet, not wall area — measure the full perimeter of every wall you're sealing, then double it, since the spec calls for two beads.
Specifications
| Tube size | 29 oz |
| Coverage | Approx. 32 linear ft per tube at a 3/8" bead |
| Type | Water-based, highly elastic acoustical sealant |
| STC contribution | 53 when applied per ASTM C-919 |
| Finish | Paintable, dries white, non-staining |
| Flame retardancy | Meets ASTM E-84 |
| Sold as | Single tube or case of 12 |
Shipping
Calculated at checkout based on your address. This product does not qualify for free shipping.
⚠️ California residents: Prop 65 Warning
Building a room-within-a-room? Email contact@homecinemasupply.com — we'll help you spec the whole assembly, not just the sealant.
