Marine varnish best for outdoors

Q. We have some good-looking outdoor furniture made of a wood called ipe. We would like to varnish it to retain the color and wood-grain appearance. Is polyurethane a good choice?

A. Polyurethane is a fine, durable finish when properly used, but it generally does not hold up well outdoors even if the container says it is for interior-exterior use. If you use poly outdoors, it could begin peeling and chipping within a year or so.

The best choice for outdoor use is a marine or spar varnish. You can usually find marine varnish at home centers and paint stores (McCloskey’s is a well-known brand).

Another high-quality marine varnish, developed for use on yachts, is Epifanes. For more information on the latter, visit www.epifanes.com.

Top-quality marine varnish is also sometimes available at high-end boat dealerships. Unfortunately, there are some drawbacks even to these outdoor-durable varnishes – they usually require multiple coats to hold up well, sometimes seven or eight coats.

Some experts say outdoor varnish will hold up longer if an epoxy sealer is applied first, but again multiple coats are necessary for good results.

Good-quality outdoor furniture made of wood will usually survive well if left unfinished. The wood will gradually take on a gray color, but the original tone can be restored by using a deck cleaner.

Pressure-treated wood or tough hardwoods can also be restored to their original color by pressure washing. Pressure-washing should be avoided on soft wood such as cedar, which can be damaged.

Q. The crawl space under my house takes on water through the north wall during rains. I use a dehumidifier to dry it out, but have to empty it manually, which is a nuisance. Two contractors said they can fix the problem, but want small fortunes. A third says he’d just dig a trench outside the wall, put in some drain pipe, and divert the water around the house. Another says nothing will work. What next?

A. I think the contractor who wants to dig a trench and install drain pipes has the right idea. Water flowing toward the north wall will be absorbed into the trench, which is filled with gravel and earth and enters a perforated drain pipe buried in the trench. The pipe carries the water to points well away from your foundation. Grass can be planted over the trench so it isn’t visible.

If you would rather continue using your dehumidifier, you can equip it with a pump that will empty it and take the water back outside through a tube.

For information on dehumidifier pumps, visit www.nextag.com/ dehumidifier-pump/ compare-html.

Q. We have moss growing in several areas on our asphalt-shingled roof. Would it make more sense to get new, moss-resistant shingles or install the zinc strips you have mentioned in several columns?

A. If you have roof-moss problems, need new shingles and are planning to install new roofing, it certainly makes sense to consider algae-resistant shingles. These shingles use an additive such as 3M’s Algae Block, which includes copper granules in the shingle coating.

Some shingles have 10-year or 15-year warranties against algae stains. However, expect to pay a premium price, since copper is expensive these days.