A.Corresponding editor Paul Fisette responds: Before finishing the interior of a basement, you must verify that the basement doesn’t leak, and that the exterior of the foundation is protected by dampproofing, good drainage, and controlled surface runoff.

I believe that applying an additional layer of dampproofing on the interior surface of the foundation wall makes sense, if only as relatively cheap insurance. I have had good luck using Sto Watertight Coat (Sto Corp., 800/221-2397; www.stocorp.com), a two-component, trowelable, cementitious compound that has a low perm rating.

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