How to Seal a Door Sill Plate

A wooden door sill plate will need sealing to prevent water damage to floors, the door frame and the floor joists beneath the floor surface. Follow these steps to seal your exterior door sill plate:

Step 1: Ensure a Snug Fit for the Door Sill

Ensure the door sill fits snugly over the base of the door frame. The door should just swing over it without making contact. Secure the door sill plate to the door frame base with galvanized nails to prevent corrosion and gaps.

Step 2: Coat the Sill Plate with Epoxy Paint

Spread a thick, smooth coat of epoxy paint all over the sill plate. Allow the epoxy paint coat to dry for several hours. Test the fit of the door over the sill plate, and lightly sand any ridges that catch the base of the door.

Step 3: Seal with Silicone Caulk

Seal any visible gaps around the door sill between it and the door frame with a water-resistant silicone caulk. Press the caulk firmly into the gaps.

Step 4: Add A Screen Door

Consider adding a screen door to your exterior to minimize exposure of the door sill plate to inclement weather.