Ask a builder

Options for rebuilding a deteriorated porch deck I plan to use a plywood overlay on an existing porch decking which is somewhat deteriorated. What is the proper type or designation of the plywood and what thickness should I use? What kind of nails? Should the plywood be sealed underneath and where the edges abut? What kind of primer and deck paint or stain should I use for best weathering?

R.L. Harrison

Mansfield, Ohio

If possible, use marine-grade plywood. Exterior-grade plywood is your next best choice. Both will last longer if sealed on both sides as well as the edges. The latter grade especially needs sealing.

Plywood thickness is related to the span between bearing points; that is, between the joists.

If the substrate is deteriorated enough, you may want to remove it. Thus, relate the thickness of the plywood to the spacing between the joists. Ask your local building department for its rules. Plywood is available in many thicknesses and grades.

Use only coated nails whenever exposed to the weather. Uncoated nails rust or otherwise disintegrate when exposed to moisture.

Finish the wood walking-deck surface with a good-quality semitransparent exterior stain. Apply two or three coats. Restain the deck as needed for maximum longevity and appearance.

There are deck paints also which are quite satisfactory. Check with your local paint dealer for his recommended deck paint and process if you prefer paint to stain.

There are built-up walking-deck processes, such as Dex-O-Tex, which are quite permanent, decorative, and serviceable. Dex-O-Tex is made by the Crossfield Products Corporation, 140 Valley Road, Roselle Park, N.J. 07204. The phone number is (201) 245-2800. The company has franchise applicators throughout the country.

Of course, there are competitors which also install quality built-up walking-deck finishes.

Observations on ways to waterproof walls

Last year you recommended Sealwall or an equivalent on a leaking concrete wall. We could not find Sealwall so we used Thoroseal, which worked. What shall I now use on a closet near the wall which has some leakage?

Mrs. E.E. Cable

Sausalito, Calif.

You apparently applied the Thoroseal according to the manufacturer's directions since it stopped the leaks. You have therefore good authority to use the same product again.

We understand that Thoroseal is a mix of cement, sand, a stearate, and sometimes a coloring agent. The stearate primarily does the waterproofing. Thoroseal meets the federal specifications for cementious waterproofing coating.

The United State Army Corps of Engineers specification, TTP-0035, requires using 80 percent fresh dry cement.

Some liquid water seals may contain only 10 percent solids. Always determine if the product meets federal waterproofing specifications.

Sealwall is a liquid concentrate mixed with cement and also meets the specification cited above. A Sealwall application is guaranteed for the life of the structure if the formula is applied according to the manufacturer's recommendations on a properly prepared substrate.

If a local outlet does not handle Sealwall, contact the company at 36300 Lakeland Boulevard, Eastlake, Ohio 44094. The phone number is: (216) 951-3445.