Paint, stains

Published on January 13th, 2013 | by Henri


Paint keeps peeling from wood-shingle siding

Q.   We have a chronic problem with peeling paint on our 50-year-old wood-shingle home. After complete sanding, priming and painting (Benjamin Moore house paint), paint will begin to peel in two years on all exposures — full sun or heavy shade though most of house is shaded by mature trees. The exception is an addition, which does not peel. We are in the process of repainting again! Can you advise any primer, paint or technique that will eliminate the problem?

An alternative is to have the house clad in vinyl siding. However, I’ve been of the opinion that siding detracts from the home’s value. Do you agree?

A.   From your description, I think you have a problem with interior moisture pushing the paint off the shingles. Although most paint failures are caused by improper preparation and/or application of the coatings, as well as from external factors such as exposure to the elements, the fact that yours fails on all sides of the old part of the house but not on the addition makes me suspect that there is another reason. Your 50-year-old house may not have a vapor retarder on the warm side of the exterior walls and it may also have had insulation blown in if the house was not insulated at the time of construction (too often the case with that vintage house).

In the absence of a vapor retarder, warm, moisture-laden air works its way mostly through any cracks in the walls’ interior finish and other avenues, such as electrical boxes, and also possibly through it depending on how permeable it is. As it cools, condensation occurs on the back of the sheathing. This condensation works through the sheathing into the shingles and pushes the paint off.

And if insulation was blown into the walls without the addition of a vapor retarder on the warm side of the exterior walls, the insulation can get wet and the same process happens. But this is more serious as wet insulation not only loses some of its R-value but structural damage can occur in time.

If you know or can find out whether or not there is a vapor retarder, and if insulation was blown in, write again and we’ll take it from there.

If I am right about your moisture problem, covering it up with vinyl siding would only hide the problem.

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