Gorilla 120339 Waterproof Patch & Seal Paste, Black, 454 g

For a leak repair that needs a flexible coating over a surface, Gorilla Waterproof Patch & Seal Paste offers a practical alternative to a simple cover-up. Its rubberized formula seals out water, air and moisture while filling small gaps and cracks. The black 454 g paste can be applied to a range of materials and painted once dry.

The essentials

This waterproof sealant forms a flexible coating that levels across the repair area, helping cover small cracks and gaps for a watertight seal. Use it on projects such as roofs, gutters, skylights, flashing, window joints and RV roofs, as well as DIY repairs around the home. It is compatible with metal, concrete, wood, aluminum, brick, tile, fabric, rubber and glass, performance can vary with plastic and rubber types.

Application is adaptable to the job: spread it with a brush, roller or trowel, or apply by dipping or pouring. That makes it useful both for working over a broader area and for filling a repair that needs careful coverage. Once cured, the coating resists temperature and UV exposure and can be painted with latex or oil-based paint. Use a primer before applying oil-based paint.

Buyers highlight effective results on repairs and value the product for quick fixes, with positive comments about its quality. Those experiences make it especially relevant when a flexible, paintable seal is more useful than a rigid filler or a surface-only cover.

Who it’s for

This paste suits DIYers and homeowners tackling exterior leak repairs on compatible surfaces, particularly where a brushable or spreadable coating can reach the affected area. For example, it can be applied across a gutter joint or around flashing, then painted to fit the surrounding finish. It is for exterior use, not continuous submersion or below-waterline repairs, and is not intended for the inside of a firebox or chimney stack.

Practical tips

Start with a clean, dry surface, free of dirt, dust, grease and oil. Stir the paste thoroughly for 30 seconds, then cover the repair area fully. Apply multiple coats where needed to fill cracks and holes, allowing each coat to cure before adding another. Do not use it for gaps wider than 1/4". Apply between 50F and 120F, and allow 24–48 hours for full cure before water exposure. A light water test can help identify any areas that need another coat.

Wipe away unwanted material immediately with a dry cloth or paper towel. Mineral spirits can be used to clean brushes and rollers. To store the can, remove excess material from the rim and press the lid shut securely.

Before you decide

What surfaces can this sealant be used on? It is listed for metal, concrete, wood, aluminum, brick, tile, fabric, rubber and glass. It may not work with every type of plastic or rubber, so consider the material of the repair surface when choosing where to apply it.

How should I apply it? Clean and dry the surface, stir the contents for 30 seconds, then apply by brush, roller, trowel, dipping or pouring. Ensure the area is completely covered, and use additional coats to fill cracks or holes, allowing curing time between coats.

Can I paint over the cured coating? Yes. It works with latex and oil-based paints, use a primer before applying oil-based paint. Let the sealant fully cure before water exposure.

Buying verdict

Choose Gorilla 120339 when an exterior repair calls for a flexible, waterproof coating that can cover small gaps and cracks and be painted to suit the finished surface. Its range of application methods and listed material compatibility make it a useful fit for roof, gutter, flashing and other DIY sealing jobs.