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    ASK THE CARPENTER

    Bounce back from rubber roof problems

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    The rubber roof on this reader’s home has become brittle and doesn’t drain properly.

    Q. The rubber-membrane roof sitting on top of our small kitchen addition was installed in 1985. You can see the little sluiceway and drain in the picture we sent. They are too high, and the roof has never drained properly. The drain is low enough that water does not run over the sides, but the water gets to about 1½ inches deep before it starts to empty. There is always water on the roof, unless we have a dry spell. The rubber has become brittle, and the surface has alligatored a bit. It also seems that the rubber is no longer glued down to whatever is underneath it. It does not leak and never has, however. My question is, after 30 years, should I replace it now, before it does start to leak? And would it be possible to add some pitch to it at the same time so it will drain properly?

    CHARLIE MEANS

    A. Just to put this in perspective, I graduated from high school in 1985, when gasoline was a buck twenty. It’s time to rip that roof off, Charlie, fix that drain, and get rid of that vernal pond on your house. To change the pitch, you’ll have to rebuild it.

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    Q. I have a black rubber roof covering my 10-by-27-foot south-facing screen porch. There is no insulation on the unfinished ceiling of the porch, and it gets very hot. I do not want to add insulation but would like to change the black roof to white to reflect the heat. The roof is in good condition. Is there a white coating that can be applied to the existing rubber roof? Can I do it myself? If there is no way to turn the existing roof from black to white, can I put a white rubber roof over the existing one? Do you have any other ideas as to how to treat the existing roof to lessen the heat?

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    NJAUDY1

    A. If the roof is 15 years old or older, I’d replace it with white EPDM (ethylene propylene diene terpolymer), which weathers better than other rubber roof membranes.

    If your roof is younger, don’t install a white membrane on top of the existing one. People who do regret it. Just paint the old one yourself.

    The EPDM Roofing Association recommends choosing an acrylic coating specifically designed for rubber roofing. They caution that you can use latex paint to cover a rubber roof, but only if you confirm with the manufacturer that it won’t interact negatively with the materials in the roof. A rubber roof should be covered with a paint layer that’s about the same thickness as a quarter, which is at least three coats.

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    You can paint just about anything. The real question is how long will it last? Like any paint project, the effort is ALWAYS in the preparation, not the application. Are the proper preparation steps worth the time and expense compared with a new roof that will last 20 years?

    Q. We had 5-inch-wide tongue-and-groove vertical cedar siding installed on our house 30 years ago. Every few years we coat it with a clear wood finish because we like the natural look. We used Flood CWF-UV the last few times. It is in need of coating again. Do you have any recommendations?

    SIDING PRESERVER

    A. All cedar products used in exterior applications require a degree of maintenance to keep them looking great, and you’ve picked a good product.

    Flood’s Clear Wood Finish, or CWF-UV, and Amteco’s Total Wood Preservative are both good choices for cedar clear coats. Both are oil-based products with paraffin added for water protection. These clear finishes will turn your wood slightly darker after you apply them, but as they dry, it will return to the original tone. Both finishes are durable.

    Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @globeaddress or @robertrobillard.