Removing Flashing Cement

Reasons for Cement Removal

• Roofs take wear and tear from the elements, heat, and age, and the cement can weaken and pull away from the flashing joint it seals. Hail can chip at the cement as well as the shingles when it strikes the roof. Snow and ice can freeze the cement, causing it to contract and crack. If the cement was improperly applied at the time the flashing was put on the roof -- such as applied to a dirty surface -- it may fail within a short period of time, allowing a leak to occur. Replacing a roof doesn't necessarily involve replacing the flashing, and new flashing can often be applied over old flashing for a better seal.

Safety Concerns

• Wait until the roof is dry before climbing up to attempt the removal of the flashing cement; wet shingles or tiles can be slippery. Wear a rubber-soled shoe or boot to provide grip while working on the roof and prevent slipping, even on dry surfaces. Use a ladder that is manufactured for your weight, with non-skid surfaces on the steps; make sure it is on a level surface before climbing. Avoid touching any power lines that attach to or dip down on the roof while you are working. If the area requiring work is on a steeply pitched roof, using a safety harness tied to a secure item, such as the chimney, is recommended.

How to Remove

• Use a chisel or pry bar to remove the shingles on either side of the area where the flashing cement needs to be removed. Do this gently to avoid damaging the shingles; they can be reattached. Using a putty knife, scrape away the old cement around the flashing and under the shingles to provide a clean surface for reapplication of new roofing cement. Removing the cement to at least a 1-inch depth should remove any loose material hiding in the cracks.

Replacement of Cement

• Once the planned repair -- replacing or repairing the flashing -- is completed, the roofing cement must be reapplied immediately to avoid leaks. Pre-mixed compounds are available and can be purchased at home supply stores. A mix of cement, sand and water can be mixed for a traditional roofing mortar; however, this may be too time-intensive for smaller cement removal jobs.