Saving Siding When You Can;

Scrapping It When You Can't

By Mike McClintock

As a house ages and shows signs of wear and tear, there are many components inside and outside that eventually present homeowners with the inevitable question: repair or replace? Nowhere does the choice you make have more visual impact than on siding.

Because no two houses deteriorate the same way or at the same rate, you can't generalize about when to re-side, or pinpoint the useful life spans of clapboards, shingles and other siding materials. Can you rescue dingy siding with a power-washing and repainting?

Should you save all that work and bury problems under new siding, or will they resurface and ruin the investment?

Basic indicators

It helps to consider the questions in two ways: the extent of problems over the surface of the building, and the depth of problems in the siding and supporting wall underneath.

Surface problems, such as formations of mold and mildew, whether isolated or widespread, generally respond to cleaning, maybe a few spot repairs in severe cases and a fresh coat of paint or stain. Power-washing often is effective, as long as you don't overdo the power part, which can erode wood grain and leak through joints into the wall.

Deeper problems, such as rot from a long-term downspout leak, require enough excavation work to reach sound material. That can mean stripping off a few clapboards or wood shingles, and cutting out a section of the plywood sheathing underneath. In some cases, you might find that a supporting wall stud has to be replaced or reinforced as well.

Repairing an isolated problem like that in an otherwise sound wall makes sense. You can weave in new siding and blend on a finish to make the repair unnoticeable. But if there are many serious problems, re-siding is likely to be a better option.

Even then, you need to make some repairs (minus the cosmetic finishing, of course) before adding a new layer. Surface scars you can let go, but not problems such as bowed siding with popped nails that can disrupt new siding no matter how well it's installed.

If old siding is on the edge of saving but has become a chronic maintenance problem, new siding may be the best option because it not only improves the appearance of your house, but also offers the opportunity to upgrade insulation and reduce air leaks.

Patching old siding

If you decide on patching with a clapboard house, trim back the damaged board to the nearest stud. Cut through the board with a circular saw (after you pull any nails in the way) by setting the depth of cut so the blade reaches just through the siding.

If you need to cut out sections on more than one board, cut each one back to a different stud to stagger the joints.

To patch damaged shakes, use a hammer and chisel to split the bad shakes into sections that you can easily pull out. Before you slip new shakes into place, you'll need to pry up the covering course and pull out the old nails.

If that risks splitting the covering shingle, slip a hacksaw blade underneath to cut the nails.

To patch interlocked courses of vinyl or aluminum siding, you need a release tool, generally called a zip tool even though the operation is more like unzipping. Fit the end between courses and slide it along the seam to release one panel from another. Most synthetics join easily end to end with a small overlap.

Even masonry siding such as stucco is patchable. In most cases, you need to add a scratch coat and a thin topcoat. The trick is to blend in both the texture and color of the repair. You might need to experiment with the mix, using a trowel, rubber float, sponge or other tool to recreate a surface pattern of swirls or dabs.

If you get a good texture match, you won't see the patch job (at least not until you're close up and looking for it) and a reasonably close color match will do.

Covering up old siding

On many houses, you can add new siding directly over an existing layer to save the trouble of stripping walls and carting away huge piles of debris. This takes careful planning, however, mainly because of the visual impact of the extra thickness at trim around windows and doors.

On some houses, the trim is prominent enough so you can slip new siding against it and avoid overlapping. It generally doesn't look good when siding covers part of the trim surface, even when new vinyl is tucked into U-shaped trim.

If there isn't room for an extra layer and you don't want to overlap, you're faced with the very time-consuming job of adding thin strips to all the trim, building it out far enough to cover the edges of the new layer.

If you have any type of brittle hardboard or cement-based shakes on the wall, you'll probably have to remove them to re-side, even if large areas are sound.

The problem is that nailing on new material fractures brittle siding into so many pieces that the surface basically disintegrates as you work. Old asbestos-based shakes might require professional handling and disposal because of the health risk from loose fibers, even outside.