Several makers sell a gutter sealant that names gutter seams and end caps, from silicone to butyl rubber. It seals small leaks; GE says gaping holes mean replacing the gutter, and sagging usually means damage that can’t be repaired.
Sealants that name gutters
| Product | Type | Rain or water | Paint | Joint limit |
|---|---|---|---|---|
| DAP Gutter & Flashing | Hybrid | 30 minutes | 30 minutes, latex | Up to 1/2 inch wide |
| DAP BUTYL-FLEX | Butyl rubber | Right away | 7 days | 1/8 by 1/8 to 3/8 by 3/8 inch |
| DAP DYNAFLEX Gutter & Narrow Seam | Hybrid | 30 minutes | 30 minutes | Up to 1/2 inch wide; runs up to 50 feet |
| GE Gutter Silicone 2 | 100% silicone | 30 minutes under GE’s conditions, otherwise 8 hours | Not paintable | Backer rod past 3/8 by 3/8 inch |
| Sashco Through the Roof! | Copolymer rubber | Not stated | 1 to 2 days, water-based | Up to 1 inch wide at 70°F or lower |
| Geocel 2320 | Tripolymer | Not stated | 24 hours | No larger than 1/4 by 1/4 inch |
DAP’s Gutter & Flashing page says 1 hour where its data sheet says 30 minutes; we use the data sheet. GE’s 30 minutes is for a bead up to 3/16 inch at 65°F and 50% humidity or more.
Sealing a seam
- Check the gutter maker’s instructions for where the sealant goes, as Loctite advises.
- Clear out debris and old sealant, and let the gutter dry; GE says dirt and moisture weaken the bond.
- On a lap joint, DAP says to run sealant along the inside edge of the joint and around the rivets or screws, and to fill end caps and slip joints before fastening.
- We’d give it the cure on the tube before the next rain, if you can.
GE’s Gutter Silicone 2 data sheet says not to use it on galvanized surfaces without the approval of the article’s maker, and it can’t be painted. DAP says its DYNAFLEX gutter runs should be 50 feet or less, because of expansion.
GE’s gutter guide is frank about the limits: sealant fixes small cracks, but gaping holes and large fissures mean replacing the gutter, and a gutter that sags or pulls away usually has damage that can’t be repaired.