How to Repair a Water Damaged Sill Plate

The sill plate can corrode when exposed to the elements.

A sill plate is the wooden horizontal member located on top of the foundation wall of a building. Because it is bolted directly into the concrete of the foundation, the sill plate cannot be replaced. It is often subjected to water damage, depending on the location of the structure. Repairing a water damaged sill plate requires a few simple materials and tools.

Things You'll Need

• Staple gun
• Waterproof wood decking sealant
• Fibrous sill sealer
• Dehumidifier
• Spray foam insulation

Instructions

Drying the Wood

1. Place the dehumidifier withing 5 feet of the middle of the sill plate in your basement or lower level of your house. Leave it there for about four days. This will remove much of the unwanted moisture from the wood.

2. Apply the sealant to the sill plate and let dry for at least 24 hours. Remember to open any windows, as breathing in most sealants is extremely harmful.

3. Apply a second coat of sealant to the sill plate and let dry for at least two days. While the sealant is drying, use the dehumidifier again to keep water out.

4. Apply the fibrous sill sealer to the sill plate using your staple gun, to pin it directly to the sill plate. Pin two staples about every 4 feet to secure the sill sealer.

5. Spray the insulation directly on the fibrous sill sealer all the way down the length of the sill plate. This is first and best line of defense against moisture in your sill plate.

Resources

• Repairing a Water Damaged Joist or Sill Plate