An Ounce of Prevention - Can Save Your Ceiling

Sometimes your only clue is a small water spot in the ceiling above your fireplace mantle.

But don’t ignore it. By the time you see it, water may have been working its way between your chimney masonry and your roof flashing for several weeks - and we all know what water will eventually do to wood.

The problem, of course, is that masonry, such as bricks, stones, stucco and mortar, expands and contracts at a different rate than the wood and roofing material that butts up against it. To seal the gap between them, roofers use both metal flashing and a petroleum-based roof cement - a thick, gooey substance that can be applied either with a hand trowel or a caulking gun.

As temperatures change on a daily basis, the roof cement is tested by the expansion and contraction of the chimney and, at a different rate, the roof around it. Making matters even worse, the roof cement has to withstand the rays of the sun beating down on it. Over time, the roof cement dries out and eventually cracks, letting water into your house.

If ever the adage "An ounce of prevention is worth a pound of cure" applies to us, this is it. Water damage to ceiling joists, plywood roof sheathing, insulation and drywall is expensive to repair. The good news is that it can be easy to prevent.

Whether or not you do it yourself or have a professional generally depends on the slope of your roof. If you can safely walk on it, have a sturdy ladder and are not afraid of heights, you may want to tackle this job yourself. If not, call a professional. It's not worth getting hurt over.

In most instances it will require two trips up the ladder, both done when there is no rain in the forecast. On trip number one take a stiff, old paint brush and a screwdriver. Use the brush to clean away dirt, twigs and leaves that have accumulated over the flashing. This will enable the old flashing to dry. Despite what the manufacturer may promise, roof cement always adheres best to a dry surface. Use the screwdriver to probe suspicious cracks or bubbles in your flashing, checking for places where the water may be entering your house.

On trip number two take a one-gallon can of roof cement and a narrow, pointed hand trowel. If your job is small, you may get by with a caulking gun and a couple of tubes of roof cement. The roof cement works best if it has been stored in a warm environment, either in your house or sitting in the sun for a few hours. Be sure to wear inexpensive gloves you can throw away afterwards to protect your skin and tennis shoes to protect your roof. Walk carefully so as not to damage the roofing.

Apply a fresh layer of roof cement over all of your flashing, making sure to work it into any cracks. Apply extra roof cement to build up low spots, especially behind the chimney, where water (or snow) can accumulate and gradually work its way through tiny cracks. It does help to be neat, so take your time. Envision where water will fall, run and accumulate, then direct it away from the chimney with the point of your trowel and plenty of roof cement.

Good Luck - And Be Safe!

- Bruce Johnson

Next Week: "English Ivy: The Silent Intruder"