Repairing A Rotted Window Sill? What You Need To Know About Rot

Updated:  December 5, 2019

Wood is such a beautiful, environmentally friendly and sustainable natural resource for your home décor.

The downside about wood window frames, though, is that they are prone to rot.

Why? Water damage. If there is even a small gap between your frame and window, rain and snow can seep through. The sill, which makes up the bottom part of your frame, is essentially a “shelf” for that moisture. If the wood remains damp and the water travels beneath trim, paint or caulk, that’s when fungi and rot start to develop.

You might think a small amount of rot isn’t that big a deal. However, if it’s left untreated for a prolonged period of time, that rot can grow, cause your sill to decay, travel to the surrounding wall area and can even lead to mould.

How To Detect Rot In Your Wooden Window Frames

Are your wood frames decaying? Start with looking at your windowsill.

Is the colour off? Is there paint peeling around the window frame? Both can indicate water damage. Look around for leaks as well. For example, you may see a small pool of water on the sill or even on the floor. Because rot can spread, look around the windows too, at the walls surrounding it.

Keep in mind, though, that wood rot is often hidden from view. Touch your window frames. How do they feel? Do they crumble when you touch them? Wood should be hard. If it’s soft, this is another indicator of rot.

Sometimes you can only tell if the wood is damaged or mouldy by looking at the inside of the frame.

How To Detect Rotted Window Sill - Weaver Exterior

Should You Fix It Yourself?

In certain cases—for example, if you’re dealing with old historic windows for which replacement is not possible—removing the rot and repairing the rotted window sill and frame with an epoxy solution is the only option.

However, while a quick Google search may make the DIY route sound easy, it is actually quite risky.

First, you need to be able to take the entire window out yourself. You will also need a whole plethora of tools including a utility knife, jigsaw, caulking gun, and drill—not to mention the ability to do exact measurements. Finally, you need to be able to put the window back in place, ensuring zero leaks or gaps.

Should You Fix Your Window Yourself - Weaver Exterior Barrie

Consider all the things that could go wrong! For example, you may think you’ve removed all the rot and replaced the window, but possibly missed something that will ultimately spread even more. You could break the window frame or glass during removal or installation. Or, while putting the window back in, you may be unknowingly creating conditions for even more moisture to get into the wood.

Replace, Replace, Replace

In most cases, if you’re dealing with rot in your wooden frames, you should consider window replacement.

There are two main types of window replacement: retrofit and tear-out (also known as full-frame). With retrofit, the new windows get inserted into the existing frame. But with tear-out, the window is taken out, all components are removed, and you get completely new windows along with new frames.

Ultimately, when it comes to wood rot, the retrofit route is only a temporary solution to the inevitable. By investing in a full-frame replacement upfront, you will be saving money in the future because you will only need to replace your windows once versus twice.

Window Replacement - Weaver Exterior Remodeling

Put A Stop To Rot

If you want to put a complete stop to rot, consider replacing your wooden frames with vinyl window frames. A popular and cost-effective option, vinyl is extremely low-maintenance. It does not peel, crack, bend or warp. It does not pit or flake. Plus, vinyl maintains its vibrancy—it does not fade.

Vinyl frames also give off a modern look: they come in a range of colours and styles, allowing you to coordinate your selection with your interior décor and exterior trim.

Finally, vinyl windows also provide solid insulation for your home, which helps you save on your energy bills.

Vinyl Window Frame - Weaver Exterior

Go With The Experts

Now you know that rot in your wooden window frames can be harmful to your home. It can also be hard to detect, and there are many risks to fixing it yourself. You may be wondering: what now?

Consult a professional window installation company.

At Weaver Exterior Remodeling, our certified experts can recognize signs of window rot and let you know the best route to take. If full-frame window replacement is necessary, we will introduce you to our collection by Vinylbilt Windows and Doors, which are rot-resistant, offer a wide range of benefits for year-round comfort, and provide energy savings.

Moreover, we believe in the quality of products so much that we offer a Lifetime Warranty on our windows at no additional charge—no questions asked!

To learn more about how we can help you, try our interactive quote tool for a free, no-obligation quote.

For more information:



replacement windows, vinyl windows, windows, wood rot, wood windows

You may also like


Weaver has over two decades of experience and provides comprehensive installation services for windows, doors, and aluminum in the Barrie region, making it a convenient option for all project sizes.