Although it may be tempting to rip out exterior trim that’s badly weathered or rotten, repair is often a better option if replacement trim would be expensive or difficult to remove. Before deciding either way, survey the extent of the rot and address its cause. Otherwise you’re treating only the symptom.
Replacing rotted sections is a good option when the bottom of an otherwise sound trim board has rotted away. Flat and square trim is easier to replace and match than molded trim. Rotted bottoms of corner boards and splashboards are usually easy to cut free and replace, whereas punky doorsills or windowsills are probably best repaired in place, using epoxy, as described in the next section.
Replacing the bottom of a rotted board is straightforward. Draw a line across the face of the board, 6 in. above the bad section. After setting your circular-saw blade to the thickness of the board, use a Speed Square to guide the saw shoe, making a 90° cut. Wear goggles and use an old blade because it may hit nails. The replacement piece should be the same thickness, width, and—preferably—species as the original trim.
To join the new section to the old, use a router with a slot-cutting bit to cut a biscuit slot in both board ends. Dry-fit everything, prime all surfaces with epoxy primer, and allow the primer to dry well. Then epoxy the pieces together. Hold the boards in place with a piece of scrap screwed to both. Give the epoxy a day to cure (or whatever the manufacturer suggests), and you’re ready to sand and paint.
In-place epoxy repairs are appropriate when the rotted area is relatively small (epoxy is expensive!) and the trim would be difficult or costly to replace. Rotted windowsills or sashes are tough to remove because both are captured by surrounding elements. Epoxy applications vary considerably, so visit the manufacturers’ Web sites (try Abatron®, ConServ®, and Advanced Repair Technology®, for example) for specifics or get recommendations at your local home center.
Use a chisel or awl to dislodge loose, crumbling wood. Suck up debris with a shop vacuum. Allow the wood to dry thoroughly before proceeding. Although it’s desirable to cut back to solid wood, soft punky wood can often be reinforced by impregnating it with a liquid consolidant. Typically, you’d drill a series of small-diameter holes into the wood and then inject consolidant into them till the wood is clearly saturated. In time, the impregnated wood will become as hard as a rock.
But, for the best bond between the consoli — dant and the two-part epoxy filler that follows, apply the putty-like filler while the consolidant is still tacky. Avoid getting epoxy on your skin, and by all means wear a respirator mask with replaceable filters when applying or sanding it. After the filler dries and you’ve sanded it to its final shape, prime and paint it. Though otherwise tough, some epoxies are degraded by UV rays, and whatever original wood remains still needs protection from the elements.
This section addresses installation of the three most common traditional sidings: wood shingles, clapboards, and stucco. Vinyl and aluminum sidings are cost-effective alternatives to traditional sidings; they’re also durable and virtually maintenance-free if correctly installed. But they’re normally a whole-house job most efficiently handled by specializing contractors and so aren’t further addressed here. Aesthetics are another consideration. Although popular in new construction and renovation, faux-grained vinyl looks phony to traditionalists. If that’s your reaction, too, consider untextured sidings, which, when painted, more closely resemble painted wood.
The information that follows assumes that building paper or plastic housewrap covers the wall sheathing and that windows, doors, and exterior trim are already installed.
