Rotted window sill

katiescarlett71October 25, 2008


My house was built pre-1916 here in eastern PA. My front window sill has become severely rotted. We are not really sure if it is original or not - we tend to think it is not.

Does anyone have instructions or knows where we can find instructions on how to replace it? Thanks!

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Since the window sits on the sill, the easiest repair is to remove it. You might find the rot extends deeper than just the sill. Depending on how the interior and exterior are finished, I would chose the side that would be the easiet to re-finish after the repair is done. Outside siding, unless it's vinyl, comes off very hard without damaging it. Inside drywall would be the easiest to replace. If the wall is insulated, you might find that it is also soaked and will need to be replaced. Not a big job, it will just take some patience and a weekend. Good Luck

    Bookmark   October 26, 2008 at 12:23AM
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I have repaired rotted sills using an epoxy wood consolidant called Liquid Wood.


First, I dug out the worst of the rotted wood, then mixed up some epoxy and applied it liberally to the remaining wood that still had some soundness. The epoxy mixture penetrates the spongy wood and when it hardens, restores it to nearly its original durability.

Abatron sells a white epoxy putty for filling in voids, but I prefer to use the Liquid Wood epoxy described above, mixed with fine sawdust. I mix up a batch of epoxy per instructions, then add sawdust and continue to stir, until a stiff paste is achieved. The paste is used to fill in the voids, and finished by smoothing with a putty knife or trowel. After it hardens, it can be sanded using an orbital power sander.

A local woodworker let me sweep up all the sawdust from his shop that I wanted. I sifted it using a piece of fine window screen, to filter out the larger pieces. You want the sawdust to be as fine a powder as possible. Dust collected from a power sander would be better still.

After hardening, the repaired spots are nearly invisible, and if well sanded, will be completely hidden after painting.

    Bookmark   October 26, 2008 at 1:42PM
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I just did this same repair this weekend.

the window sill was damaged as the caulk had broken down where the sill meets the siding. I found it while re-caulking.

So, I also purchased an epoxy for wood repair and a wood hardener (recommended for use with the epoxy I purchased). I then dug out all the old spongy wood, not too big of an area luckily. I carefully cleaned the wood with a brush and air duster. I then applied the wood hardener and then the wood epoxy. It is very hard right now. I just need to go back and put some paint on it and finish caulking.

If the area is not that large then you should be able to fix it easily.
The repair I did was about 30 min. Next summer we may try to remove a piece of the siding to verify that I got all the rot out. However, we knew the rot wasn't that bad as we had just hung window boxes and the screws held very tight. The screws were only about 6 inches from where the rot was.


    Bookmark   October 28, 2008 at 12:07PM
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Are you referring to the exterior window sill that is usually integral with the window frame or the interior window stool that is usually a trim piece?

    Bookmark   November 8, 2008 at 10:15AM
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