How to Repair Wood Siding - Pro Construction Guide
How to Repair Wood Siding

How to Repair Wood Siding

By Chad McDade

Wood siding is a durable and long-lasting exterior cladding option that has been used on homes for centuries. One of the downsides of this type of siding, however, is the maintenance it requires. Wood siding needs to be repainted and caulked on a fairly regular schedule. Without this maintenance regimen, water will begin to seep into voids and seams, causing water damage that can become severe. In addition to lack of maintenance, wood sided homes can, over the years, undergo changes to the structure without proper consideration to water penetration. Here is how to repair wood siding.

Water-damaged siding around window was removed to reveal damaged wall sheeting

Water-damaged siding around window was removed to reveal damaged wall sheeting.

In a recent project, I was contracted to make repairs to a home with painted plywood clapboard siding. The majority of the siding had been well maintained, but some of the original windows had been replaced. These new windows had not been properly flashed. In fact, the original head flashing had been cut away, and the new windows had simply been caulked to the siding. This was the only method of water protection provided.

It worked until the caulking cracked, and then water began to penetrate, rotting the plywood siding and the black Celotex wall sheathing behind it. In addition to the water damage, ants were drawn to the area, and the ants drew the attention of a woodpecker that created holes in the siding to get to the ants. Once the ants were discovered, the job was placed on hold until an exterminator could come on site to treat the ant problem. Then, construction continued.

An oscillating multi tool was used to cut out damaged sections to repair wood siding

An oscillating multi tool was used to cut out damaged sections of siding.

The first step to repair wood siding was to remove the damaged siding. Many of the pieces were the full length of the wall. In order to keep the project within budget, we cut the siding past the damaged areas. The cuts were made with an oscillating multi-tool, which let us cut out the damaged pieces with minimal impact on the other siding pieces. Next, we removed the damaged Celotex wall sheathing and replaced it with new. Since Celotex isn’t a common building material anymore, we used OSB (oriented strand board) of a similar thickness to repair it.

Once all the water-damaged sheathing was removed, the next step was to flash the windows to prevent any future damage. This was accomplished with a combination of site-made aluminum flashing and peel-and-stick flashing tape. The final step was to replace the siding.

Flashing tape on new head flashing

Flashing tape on new head flashing is shown.

The original plywood lap was not available, so the homeowner opted to use LP Smartside, since it was a locally available siding in the required 12-inch reveal width. Before the siding was installed, we applied a coat of primer and one coat of Glidden Premium exterior paint. We were able to blind nail some of the new siding in the areas that had multiple courses replaced. In smaller areas – and where the new siding joined the old – we had to face nail. The holes left from face nailing were filled with an exterior painter’s putty and sanded smooth.

Flashing tape on new head flashing is shown

Flashing tape on new head flashing is shown.

During the installation, we placed 4-inch-wide x 14-inch-long pieces of aluminum behind the butt seams that we’d created. Then we sealed the butt seams with OSI Quad sealant. Where the siding butted into the window trim, we removed all of the old caulking from around the window perimeter and re-caulked it with OSI Quad. After the siding was installed, we applied a second coat of paint to seal everything up. In conjunction with the siding replacement, one window had a rotted sill. That was removed, replaced with new wood, and covered with aluminum trim coil.

To repair wood siding sections of damaged siding were removed.

Sections of damaged siding were removed.

While not a perfect match to the old siding, the new LP Smartside is close to the original look. After the second coat of paint was applied, it was hard to discern a difference.


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