Great Stuff Gaps & Cracks Insulating Foam Sealant (12 oz) Review (2026)
By Nate Sawyer, Editor · Updated July 2026
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- Air sealing
- Filling large gaps
- Pest blocking
A high-expansion polyurethane foam that quickly fills large, irregular voids up to 3 inches, ideal for rim joists, penetrations, and pest-blocking. The closed-cell foam adds R-value and blocks air and drafts cheaply. Cautions: it expands aggressively and can bow window or door jambs in tight frames, and cured foam is nearly impossible to remove.
Pros
- High expansion fills big voids fast, so one can covers a lot of rim-joist and penetration sealing
- Closed-cell foam adds real R-value and blocks air, drafts, and small pests
- Cheapest way to seal large irregular gaps compared with backer rod plus caulk
Cons
- Expands aggressively and can bow window/door jambs if used in tight frames
- Sticky and nearly impossible to remove from skin, clothing, or trim once it cures
- Straw can clog after one session, so leftover foam in the can is usually wasted
Specifications
| Type | Polyurethane expanding foam (closed-cell) |
|---|---|
| Expansion | High expansion, fills gaps up to 3 in |
| Cure | Tack-free ~20 min, cut/trim in ~1 hr, full cure ~8 hr |
| Paintable | Yes, after full cure (sand first) |
| Use | Gaps and cracks up to 3 in, indoor/outdoor |