Flat Roof Leak Repair

Remove Damaged Portion

With the utility knife, cut out the damaged portion of the roofing. Cut at least one to two inches beyond the damaged area to make sure that the entire damaged area will be addressed in the repair.

Clean Damaged Area

Brush away large pieces of debris like pebbles, twigs, or leaves. Brush away rust from fasteners or flashing.

Wearing waterproof gloves, use the cotton rags and mineral spirits to clean the patch area and several inches beyond. Let the mineral spirits dry for a few minutes.

Cut Reinforcing Tape to Size

Measure the size of the area to be patched. Cut reinforcing tape to cover this size, plus another two inches beyond the patch. Multiple rows of reinforcing tape can be overlapped.

Fill Depression With Wet Patch

Water will pool and potentially leak in depressions, so they must be raised to the level of the surrounding roof deck. Use the putty knife and wet patch to fill in the depression. Proceed immediately to the next step to avoid the patch from drying up on you.

Apply wet patch in temperatures greater than 0° F and less than 120° F. Though most wet patch repair products can be applied to wet surfaces, dry surfaces usually yield the best results.

Set Reinforcing Tape

Set the reinforcing tape loosely on the wet patch material. Wear waterproof gloves and safety glasses. The tape should be flat. Folds, buckles, ridges or creases will allow water to enter the patched area.

Embed Reinforcing Tape

Press down on the patch tape with the putty knife. To avoid dislodging the patch tape, hold one end down with a gloved hand. Then, run the putty knife along the length of the patch tape, applying light pressure. The tape should sink into the wet patch material.

Apply Top Layer of Wet Patch

With the putty knife, apply a top coat of wet patch, extending the patch two to four inches beyond the lower patch. Apply the wet patch from 1/8- to 1/4-inch thick. Feather out the edges of the wet patch into the surface of the roofing material. Avoid creating ridges along the edges that can peel up over time.

Clean Tools

Immediately clean tools with mineral spirits before the wet patch dries. The flat roof patch should be cured in about two hours.