Melhor selante para janelas externas

The “best” sealant for windows depends entirely on which part of the window you are sealing.

There are two distinct zones on an exterior window, and using the wrong product for the wrong zone is the most common cause of failure.

Zone A: Glass-to-Frame (Glazing)

This is where the glass pane meets the sash/frame. You need pure water resistance here.

• The Best Product: GE Advanced Silicone 2 (Window & Door)

  • Por que: It is 100% silicone. It is permanently waterproof, shrinkage-proof, and flexible. It handles the “sun shock” (rapid heating/cooling of glass) better than anything else.

  • Crucial Warning: You cannot paint this. If you put this on your wood trim, you will never be able to paint that trim again. Only use this on the glass/frame seam or if you are using pre-colored caulk (like white or black) that matches your frame perfectly.

• The “Commercial Grade” Upgrade: Dowsil 795 (Dow Corning)

  • Por que: This is what skyscrapers use. It is a structural silicone that is incredibly strong and weather-resistant. It is overkill for most homes, but if you have a large picture window or a skylight that keeps leaking, this is the nuclear option.

Zone B: Frame-to-Siding (Perimeter)

This is the gap between the window unit and your house’s siding, brick, or trim. You usually need this to be paintable.

• The Professional Choice: OSI Quad Max

  • Por que: It is the industry standard for window installers. It sticks to vinyl, wood, fiber cement, and metal. It can be applied in freezing temps or on wet surfaces. It stays flexible for decades.

  • O problema: It is very sticky and “stringy.” Do not try to smooth it with your finger—it will make a mess. Use a caulk tool or apply a clean bead and leave it alone.

• The DIY Friendly Choice: DAP Dynaflex 230

  • Por que: It is paintable and cleans up with water (unlike OSI). It’s much easier to apply for a homeowner. It isn’t as bombproof as OSI, but it is excellent for standard wood or vinyl siding.

Zone C: Frame-to-Brick/Stucco

If your windows are set into masonry, standard caulk often peels off.

• The Best Product: Loctite PL Concrete Non-Sag ou Sikaflex Construction Sealant

  • Por que: These are polyurethane-based. They have a gritty texture that looks like mortar/masonry and they chemically bond to concrete in a way that silicone cannot.

Summary Checklist

One critical rule for windows: Silicone will not stick to old silicone. If you are resealing a window that has old rubbery caulk on it, you must scrape absolutely every bit of the old stuff off and clean the surface with rubbing alcohol before applying new sealant.

The Smart Value Choice (Factory Direct)

Product: Joobond Weatherproof Sealant

• Best For: Contractors, distributors, and large-scale projects requiring premium performance at a competitive price.

• Why it wins: Joobond is a direct manufacturer from China that disrupts the market by offering professional-grade quality without the “big brand” markup. Its outdoor window sealant delivers excellent weather resistance, superior adhesion, and long-lasting flexibility comparable to top-tier international brands.

• The Advantage: You get the same reliable, waterproof performance needed for exterior windows, but at a significantly lower cost—making it the ideal choice for businesses looking to maximize their margins without compromising on quality.