If the gap between the window frame and wall is deep, you cannot fill it entirely with caulk (it will shrink and crack).
If the glass itself has a crack at the edge compromising the seal:
| Sealant Type | Best for | Pros | Cons | |--------------|----------|------|------| | 100% Silicone | Glass-to-frame, exterior | Extremely flexible, waterproof, UV-resistant | Not paintable, difficult to remove | | Polyurethane | Frame-to-wall (masonry/wood) | Very durable, adheres to many surfaces | Requires solvent cleanup, shorter shelf life | | Acrylic Latex | Interior only | Paintable, low odor, water cleanup | Less flexible, not weatherproof | | Butyl Rubber | Older metal frames | Good adhesion to metal | Messy, shrinks over time |
Recommendation: For exterior fixed windows, use high-grade silicone (e.g., GE Supreme Silicone or Dow 795) for glass-to-frame, and polyurethane (e.g., SikaFlex) for frame-to-wall masonry gaps.
Depending on your diagnosis, you will use one of three methods. We will start with the most common DIY fix for a fixed picture window: Reglazing and Caulking.
For glass-to-frame resealing: Load your caulking gun. Cut the nozzle at a 45-degree angle to a diameter slightly larger than the gap. Puncture the inner foil.
For frame-to-wall resealing: Use OSI Quad or high-grade polyurethane for exterior. These remain flexible for 50+ years.
Most DIY reseals fail in under a year. Here is why:
| Mistake | Result | Fixed Solution | | --- | --- | --- | | Used latex caulk outside | Cracked in 6 months | Use polyurethane or silicone | | Did not remove old sealant | New caulk peeled off | Scrape to 100% bare surface | | Sealed over wet wood | Blistering and mold | Dry with heat gun + apply primer | | Filled a deep gap entirely | Shrinkage cracks | Use backer rod (1/3 depth rule) | | Smoothed silicone with dry finger | Poor adhesion | Use mineral spirits or soapy water |
If you follow the steps above, your fixed window reseal will last 10–20 years for silicone and 30+ years for polyurethane.
If the gap between the window frame and wall is deep, you cannot fill it entirely with caulk (it will shrink and crack).
If the glass itself has a crack at the edge compromising the seal:
| Sealant Type | Best for | Pros | Cons | |--------------|----------|------|------| | 100% Silicone | Glass-to-frame, exterior | Extremely flexible, waterproof, UV-resistant | Not paintable, difficult to remove | | Polyurethane | Frame-to-wall (masonry/wood) | Very durable, adheres to many surfaces | Requires solvent cleanup, shorter shelf life | | Acrylic Latex | Interior only | Paintable, low odor, water cleanup | Less flexible, not weatherproof | | Butyl Rubber | Older metal frames | Good adhesion to metal | Messy, shrinks over time | how to reseal a window fixed
Recommendation: For exterior fixed windows, use high-grade silicone (e.g., GE Supreme Silicone or Dow 795) for glass-to-frame, and polyurethane (e.g., SikaFlex) for frame-to-wall masonry gaps.
Depending on your diagnosis, you will use one of three methods. We will start with the most common DIY fix for a fixed picture window: Reglazing and Caulking. If the gap between the window frame and
For glass-to-frame resealing: Load your caulking gun. Cut the nozzle at a 45-degree angle to a diameter slightly larger than the gap. Puncture the inner foil.
For frame-to-wall resealing: Use OSI Quad or high-grade polyurethane for exterior. These remain flexible for 50+ years. For frame-to-wall resealing: Use OSI Quad or high-grade
Most DIY reseals fail in under a year. Here is why:
| Mistake | Result | Fixed Solution | | --- | --- | --- | | Used latex caulk outside | Cracked in 6 months | Use polyurethane or silicone | | Did not remove old sealant | New caulk peeled off | Scrape to 100% bare surface | | Sealed over wet wood | Blistering and mold | Dry with heat gun + apply primer | | Filled a deep gap entirely | Shrinkage cracks | Use backer rod (1/3 depth rule) | | Smoothed silicone with dry finger | Poor adhesion | Use mineral spirits or soapy water |
If you follow the steps above, your fixed window reseal will last 10–20 years for silicone and 30+ years for polyurethane.