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Ask the Carpenter: When shingles won’t hold paint

Ask the Expert Home Improvement
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Q. We have a house on Cape Cod near water. We started to paint the wooden shingles, but they don’t seem to want to hold the paint. Also, there are areas with mold/mildew that do not get sun. We are thinking about reshingling. What is your opinion? Will new cedar shingles help the mold/mildew issue? We would leave them unfinished.

MAUREEN

A. I’m wondering how old your shingles are, what shape they’re in, and whether water is getting in behind them somehow. Make sure your window, roof, and sidewall flashing is intact and working. Do you have gutters? Not having them can wreak havoc on sidewall siding. Unfortunately, without more information, it’s tough to advise you on this.

If you do opt to re-side, use a quality house wrap to provide good water drainage. The purpose of house wrap is to prevent the entry of moisture into the wall cavity. House wraps also provide continuous membrane protection, covering all cracks, gaps, and orifices between the exterior sheathing and the rigid foam insulation. In certain instances, house wrap can also act as an air barrier when the seams are taped. A good house-wrap material must provide waterproof protection and have a high moisture vapor-transmission rate to be considered effective.

Install all new flashings at doors, windows, and sidewalls. Ensure that your new siding is pre-primed and that your installer primes all cuts and end grain.

 

Q. I have an enclosed front porch with a hardwood floor. It has storm windows and a steel front door that leads to a landing with stairs to the sidewalk. The foundation of the front porch is stucco-covered concrete blocks. When it rains or snows, the wood floor gets wet. It seems like water is coming up from below. There are no vents, just a roughly 3-by-4-foot opening under the stairs. I don’t believe that there is any insulation or vapor barrier under the floor. Any recommendations?

JACK DAHLSTEDT

A. You mention stairs, so I’m assuming this porch is not at ground level. If that is correct, I would look for a roof, window, or flashing leak. Also, does the exterior siding extend past floor level, or does it terminate on a concrete floor-slab shelf? If you have a shelf, water is probably coming in at that seam.

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 @robertrobillard. Subscribe to the Globe’s free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp.