How To Repair Exterior Rotted Wood On A Window Sill

Repairing a Rotted Window Sill – Over time our homes start to develop wear and tear from the seasonal elements, especially Toronto homes that experience 4 different weather changes each year. Occasionally a repair on the exterior of our house will need to be done that a slab of paint alone can’t fix. This project is for those who have a bit of prior handyman experience.


How to Repair Exterior Rotted Wood On A Window Sill

Materials That You Will Need to Repair Exterior Rotted Wood on a Window Sill

• Putty Knife
• Pry Bar
• Claw Hammer
• Wood Chisel
• Circular Saw
• Utility Knife
• Pencil
• Hand Plane
• Table Saw
• Cedar/Redwood Lumber
• Drill and Various Drill Bits
• Epoxy Wood Filler
• Sand paper
• Caulking
• Exterior Wood Primer
• Exterior Wood Trim Paint

1. Prep Rotted Window Sill

-Break the caulked seal along the rotted window sill with a utility or putty knife. Scrape the paint off of the window sill closest to the wall and partially pull out old nails with a pry bar. If you would like to save the wood, finish taking the nails out with a claw hammer to avoid damaging the trim. You should be able to pry the entire unit out as one piece.

-Chip out any remaining rot in the sill with a wood chisel and hammer.

2. Cut the Exterior Rotted Wood

-Now you need to cut off the 2window sill part that extends past the siding. This is usually the rotted part. If this doesn’t come out as one piece, use a pencil to draw a straight line and cut along it with a circular saw. Use an oscillating blade to cut the part of the window sill the circular saw can’t cut. Smooth out the cut with a hand plane.

-You’ll need to cut a new sill or get a replacement strip from cedar lumber or redwood using a table saw. You can use the old window sill or cut piece as a template.

3. Drill the Window Sill

-Drill the new window sill into the waterproof construction adhesive and clamp it together by drilling 3 ½ inch deck screws through the plastic and into the wood about ¼ inch.

4. Fill Epoxy Filler to the Rotten Window Frame

-Using an epoxy wood filler, fill in the screw holes and sand it out once it has hardened. Caulk along the edges of the new window sill with an acrylic latex caulking and replace the trim with new properly measured trim or by using the old existing trim. Fill in any nail holes that you may find caulk and sand it out.

5. Prime and Paint the Window Sill

-Using an exterior wood primer, prime the window sill with two coats – let dry. (Determine how long to wait for the primer to dry based on the label on the primer)

-Paint over the primed Window sill with the desired colour of exterior trim paint and let dry.

Like most wood, over time it will rot. If your exterior wood trim has been neglected and not well maintained, the seasonal weather changes will definitely create a rotting issue. So after this repair – keep regular maintenance of your exterior wood trim by using a waterproof wood sealer and checking periodically for cracks and issues so you can fill them in before the wood begins to rot. Doing this keeps the exterior wood trim looking attractive!

Repairing exterior rotted wood on a window sill can no doubt be a tricky job. For the amateur handyman who needs a little guidance, these steps might have made this tricky job an easy one. For those of you without any prior handyman experience on repairing rotten window frame and for those who don’t have the time to invest into this project, why don’t you call Home Painters Toronto ? We’ll do it for you! Call us NOW at 416-494-9095…… For more handy tips, check out the blog Tips for Painting Your Wooden Exterior Trim.

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