Do It Yourself: Moisture can cause peeling wood frames

Q. My house has a lot of wood-framed windows and every spring I have to check for peeling paint on the outside frames, especially the sills. I use good paint but on some sills it only lasts a couple of years. What causes this and how can I correct it?

A. The cause is generally moisture from rain, snow or window condensation. The moisture gathers on horizontal surfaces like window sills and porch railings and eventually works its way into the wood, either through the paint film or through poorly caulked joints.

If any of the paint was applied before 1978, you should test it for lead before proceeding. Lead-paint test kits are sold at most home centers and on the Internet. If lead is present, it is best to have an experienced professional painter handle the work.

For best results, if your paint passes the no-lead test, scrape off all loose paint and use a good paint stripper such as Strypeeze to remove the remaining paint. Sand the sills and fill any cracks or holes with an exterior-grade spackling compound.

Some painters like to apply a water-repellent preservative to the bare wood at this point. This is a good step, but if you use a WRP make sure it is a brand that can be painted over, such as Woodlife Classic.

Next, caulk the joints at the sides of the sills. Again, make sure you use a paintable product; a high-quality acrylic-latex window-and-door caulk is fine.

Wait about a day for the WRP and caulk to become thoroughly dry and apply a good water-based primer such as Bulls Eye 1-2-3. When the primer dries, you should apply two coats of top-quality acrylic paint. A semi-gloss paint is a good choice for exterior trim.

Follow the same steps for other troublesome parts of your exterior window frames. This procedure should extend the life of the paint, but if you want even less future maintenance, have the sills and frames capped with vinyl or aluminum.

Q. Bats are nesting behind the vinyl siding installed over the original siding on my house. They gain entry at the corners where there are gaps between the siding and corner fittings. I don’t want to kill them, but is there any way to get rid of them?

A. Vinyl siding needs to expand and contract with temperature changes, which is why there are gaps at the fittings. If you seal the gaps with caulk, it will prevent the movement of the siding and probably cause it to ripple.

However, since you don’t want to harm the bats, your first problem is to get them out of the siding. If you know where they are hanging out, thumping on the siding at intervals during the day might convince them that they have picked a bad place to sleep. The bats should emerge at dusk, when they begin hunting for insects such as mosquitoes, so you can probably pinpoint their general location by watching.

Once the bats are out hunting, you can close the entry-exit gaps with a material like foam weather-stripping, sold in rolls at most home centers. This should close the gaps while still letting the vinyl siding move.

Because bats don’t gnaw like rodents, this might keep them from getting back in.

You should also seal other gaps around your house, using caulk and/or weather-stripping. This will not only help keep out unwanted critters and insects, but improve your energy bills.

A more drastic measure would be to temporarily remove the siding panels in the area the bats inhabit; a vinyl-siding contractor can do this quickly and easily.