Many houses are covered with some kind of siding: aluminum, vinyl, or wood, installed either horizontally (e.g., clapboards) or vertically (e.g., board-and-batten). Although aluminum and vinyl siding are largely maintenance free, their surfaces can still fall victim to scratches, cracks or dents, and individual pieces can come loose. While the damage can be repaired, it's usually noticeable, so it is best used in a less noticeable area, or artfully hidden behind vegetation.

Siding also needs a good annual cleaning. Use a power washer (which you can rent) to spray the siding, washing from the bottom up to the top of the house, and rinsing from the top down. Work in the shade or on a cloudy day, and avoid driving the water up behind the siding. If needed, a nonabrasive cleanser can be added to the power washer; follow the washer's instructions to pick the right cleanser.

Repairing Aluminum Siding

For small scratches or rusty areas on aluminum siding, use a wire brush or sander to remove loose paint or rust. Take the surface down to the bare metal. Prime and then paint the area with metal paint to match the rest of the siding.

Dents in aluminum siding can be fixed by drilling a hole through the dent. Place several washers over a self-tapping screw, and insert the screw into the hole. Use pliers to pull on the screw head-as you pull on the screw, the dent will come up as well. Remove the screw and fill the hole with aluminum or steel filler. When it's dry, sand it smooth, and prime/paint it to match the surrounding surface.

Larger cracks or damaged areas may mean that you have to patch the damage. First, cut away the damaged area using tin snips. Make a vertical cut on either side of the damage, extending just above the damaged area but not up through the nailing strip on the top edge of the siding. Cut horizontally between the vertical cuts to remove the damaged area.

Cut a patch sized at least 3 inches longer and wider than the damaged area, removing the nailing strip. Apply roofing cement around the area on the siding where you cut out the damaged area, and to the back of the patch. Place the patch over the gap, and press firmly to seal it.

Repairing Vinyl Siding

You can tackle small cracks in vinyl siding with a siding repair kit from your home center or siding supplier. Gently lift up one edge of the crack, apply the repair glue inside it, and press the edges down firmly. Work on a warm day, when the vinyl will be pliable (it can crack or break when it's cold).

For larger cracks, replace the damaged area. The bottom edge of each piece of siding is shaped like a J so that it bends back and under the upper edge of the siding underneath it. You'll need a zip tool to unlock the two pieces of siding where the damaged areas need to be replaced. Slide the zip tool up, under, and along the J-channel, pulling down slightly (persevere, because this can be a hassle). Wedge the overlapping siding up to give yourself room to work on the damaged piece.

Cut through the damaged piece from its bottom edge right up through the nailing strip (try to remove enough length that you have at least two studs to nail the replacement into). Remove the nails and the damaged piece. Cut a replacement piece that's about 4 inches longer than the damaged piece. On the replacement, cut away the nailing strip 2 inches from either end so that the nailing strip will fit into the original area but the siding itself will overlap the existing siding by about 2 inches on either side. (If you don't have a replacement piece of siding, glue a patch onto the back of the damaged siding and use it as the replacement.)

Insert the replacement siding. It's tricky to drive the nails into the nailing strip, because the strip is tucked up under the overlapping siding. With the overlapping siding still wedged up a little, place your ring-shank siding nail or roofing nail in the nailing strip. Place the end of a pry bar over the nail, and strike the pry bar with your hammer; this should drive in the nail. Then, use the zip tool to relock the J-channel.

When you're nailing aluminum or vinyl siding, never drive the nails all the way in. The long slots in the nailing strips are designed to let the siding expand and contract. If the nails are too tight, the siding can buckle or warp. Leave the nail heads above the surface just a little.

Repairing Wood Shingles or Siding

Small holes in wood shingles or siding can be filled with wood putty, sanded, and then painted to match the rest of the wood. Cracks can also be fixed in place. Gently widen the crack with a putty knife or chisel so that you can apply an exterior-grade wood glue to both its edges. Press the pieces back into place and insert screws (predrill the holes to avoid splitting the wood) on both sides of the crack to further strengthen the repair.

You can try to straighten warped wood siding by inserting screws into predrilled holes through the warped board into the wall studs. Otherwise, you'll need to replace the board.

To replace damaged siding that doesn't have an overlapping style, cut around the damaged area, pry up its nails so that you can remove it, and nail a replacement into place.

Board-and-batten siding can be removed by prying up the thin battens that cover the joints between the boards. Remove the nails in the damaged area, take out the damaged wood, and replace it, leaving a ⅛-inch expansion gap on either side. Caulk the seams, and then replace the battens.

For overlapping styles, carefully pry up and wedge the board or shingle that overlaps the damaged area so that you have room to cut around the damaged piece (you may need to cut it into several pieces along its length). Slide a hacksaw blade up under the damaged wood or shingle(s) to cut off its nails flush with the wall surface. Remove the damaged area, and slide the replacement wood or shingle as far as possible into place. With a block of wood protecting the wood's bottom edge, tap it completely into place. Predrill holes, and nail or screw the shingle to secure it. Caulk the nail holes and the seams between the existing siding and the replacement, and finish to match the existing siding.