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How to Repair Exterior Rotted Wood On A Window Sill

How To Repair Exterior Rotted Wood On A Window Sill, painting window frames

Over time our homes experience wear-and-tear from the seasonal elements. Especially for Toronto homes, we experience everything from heavy snow in the winter to balmy summer torrential downpours. Occasionally a repair on the exterior of our house will need to be done that some fresh exterior painting can’t fix. This project is for those who have a bit of prior handyman experience. So, let’s dig right into what you’ll need and how to repair exterior wood on a window sill.

How to Repair Exterior Rotted Wood On A Window Sill

painting window frames, Exterior Window Sill White Repairing Rotted Window Sill

Materials Needed

  • • 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.

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Prep Rotted Window Sill

Step - 1 Prep Rotted Window Sill

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2. Cut the Exterior Rotted Wood

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Cut the Exterior Rotted Wood

Step - 2 Cut the Exterior Rotted Wood

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• Now you need to cut off the window 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.

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Drill the Window Sill

Step - 3 Drill the Window Sill

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4. Fill Epoxy Filler to the Rotten Window Frame

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Fill Epoxy Filler to the Rotten Window Frame

Step - 4 Fill Epoxy Filler
to the Rotten Window Frame

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• 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!

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Prime and Paint the Window Sill

Step - 5 Prime and Paint the Window Sill

By Home Painters Toronto

Wood Restoration Carpentry & Repair

Maybe now’s the time to really think about fresh exterior painting?

Now that you’ve figured out how to repair exterior rotted wood on your window sill, you have the chance to stand back and really take a look at your home. Are you really happy with the overall look of your exterior painting? How about the window trims and soffits and eaves? If you want a uniform look but totally refreshed, now is the time to take action.

When you’re trying to think about a new look for the exterior of your home, you always want to consider the overall design aesthetic of your neighbourhood. Are they mostly classic homes or have they just recently been built? Take a look at some of the different colour schemes, especially in terms of brick and siding. Follow suit and maybe put your own spin on things when you decide to do this yourself. For some of the top colours for aluminum siding, visit this blog here!

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If you reside in Toronto and the GTA and need some help with your exterior painting, don’t hesitate to call us! We will help you pick the colours you want and show you the latest painting and home renovation trends. Our home painting services with the best pro painters have been around now for over 30 years. Call 416.494.9095 or email brian@HomePaintersToronto.com for a FREE quote for your home painting needs. And don’t forget to check us out on our social media channels below! 

Brian Young - Home Painters Toronto

From The Owner & Founder


Hello and welcome!

I’m both deeply honoured and flattered you are considering using our services.

Since 1987 when I was at York University simply earning my way through school, I’ve had the privilege to meet and work with thousands of amazing homeowners like yourself.

Besides the birth of my daughter, there is nothing more satisfying than seeing a homeowner’s life change when we have transformed their dream home into a masterpiece. For that reason, we take our jobs very seriously and are committed to our cause.

At Home Painters our mission is to paint homeowners’ dreams, and make your painting experience last a lifetime!
I look forward to hopefully meeting you one day, as it brings me tremendous joy to make homeowner’s dreams come true.