Use stripper before staining deck

Q. I have a very ugly, accidentally two-toned wood deck, the result of trying to apply a light-colored semitransparent stain over a dark one. Both stains are oil based. I cleaned the deck with a bleach cleaner but it is still a mess. Should I apply a solid-color stain to get a uniform color? Are oil-based stains more likely to attract mold?

A. Cleaning isn’t enough to remove old stain before re-staining with a lighter colored semitransparent stain. In order to prepare the wood for new stain and restore the surface, you should use a deck stripper to remove all the old stain. Be sure to buy a stripper that will remove oil stain – some strippers will work only on water-based stains.

When the old stain is removed, you should clean the deck again – either by pressure washing or using a bleach-type cleaner – rinse thoroughly, and let it dry. Then you are ready to restain with a semi-transparent.

Solid-color stains, which are much like paint, have superior hiding ability and are often the choice for decks that do not have attractive wood. Some solid-color stains can also be used over previous coatings that are in good condition and adhering well (be sure and check the directions on the container for information).

Solid-color stains are sometimes given high marks for long-lasting good looks and are especially good on vertical surfaces like siding and fences. But, since they are much like paint and basically lay on the surface, they will sometimes peel and wear easily.

Also, many experts recommend semi-transparent stains for wood decks. Semi-transparents, which penetrate the surface of the wood, have good adhesion and let attractive wood grain show through.

Some critics of oil (alkyd) stains say they attract mold easily, but the fact is that mold and mildew can attack virtually any stain or coating if moisture and/or excessive shade are present.

Oil-based stains remain popular, partly because they have excellent penetration and wear-resistance. Some of the top-rated stains have alkyd formulas. There are also acrylic-alkyd blends that permit easy water cleanup.

Basically, if you want to hide unattractive wood and get an evenly colored surface, use solid color. Otherwise, stick to a top-rated semi-transparent.

Q. The attic floor in my older house has some insulation between the joists. However, there is no insulation where air-conditioner ducts runs between the joists, and the pull-down attic stair is not insulated. How can I improve this?

A. Heating and air-conditioning ducts running through attics and other unconditioned spaces should be sealed and insulated. Ducts without insulation will result in the loss of expensively cooled or heated air into a space where it is useless. The stair is also a major source of conditioned-air loss.

Before attempting to insulate the ducts, the joints between duct sections should be sealed. Pros use special mastic or tapes, which can be bought at some home centers or by searching the Internet with the words “duct sealant.” Do not use ordinary cloth-backed duct tape – despite the name, it will come loose and prove useless.

Once sealed, ducts that are accessible can be insulated with special foil-faced duct insulation called duct wrap. When ducts are tight against the floor and can’t be conveniently insulated, a granular type of insulation such as cellulose is sometimes simply poured over the ducts, burying them.

For more information on duct sealing and insulating, visit http://ducts.lbl.gov.

The pull-down stair can also be insulated. An insulating kit (about $137) is available at www.alwaysbrilliant.com. Enter “attic stair cover kit” in the search space.