A.Corresponding Editor Paul Fisette responds: I would recommend that you use a layer of #15 asphalt felt to cover the T&G boards. The new siding will not keep all rainwater out, especially in a heavy soaker of a storm, and the T&G boards need to be protected from water that penetrates the siding.

If you installed a second layer of plastic housewrap instead of asphalt felt, and liquid water were to leak into the region between the two layers of housewrap, the T&G boards could have a difficult time drying out. Asphalt felt is forgiving. Initially it blocks vapor and liquid water, but if it does get wet (under extreme exposures) it...

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