Home maintenance can feel like a full-time job, especially when you have an older house. Wood frames don’t last forever, and when you are faced with rotting window frames, you might be tempted to rip out the entire frame and replace it, which is a costly option. How can you repair a rotted window frame?

Repairing a rotted window frame includes inspecting the frame for rotten areas, and removing those with a chisel. Then drill holes in the healthy wood and stabilize any crumbly areas with a wood hardening product. Fill the gaps with wood epoxy, let dry, sand the area, and paint.

Follow these steps in case your window frame is salvageable. If it’s not, keep reading to learn how to replace it as well.

Inspect the Frame for Rot or Spongy Areas

Before determining if you need to repair or replace your rotted window frame, inspect the framing for spongy areas that indicate it’s rotten. Doing this will help you discover the extent of the damage and where you need to repair the frame.

Often, a damp and humid climate will damage a wood window frame beyond repair, and replacing it may be your only option.

Signs of a Rotting Frame

When the window frame has peeling paint with significant decay in the frame, it is obvious that it is rotten. However, there are other less obvious signs that a frame is rotting in certain places. If there is discoloration in certain areas of the frame, that might mean that there is extensive moisture and rot in that area. Or, it could mean that there is mold in that area.

Another way to determine rot is by pressing your fingers gently around the frame. If there are spongy areas, then that could be an indication it is rotten. If there are significant areas that are spongy or soft, a partial replacement might be a better option. But if there is only a small area that is soft, then repairing is less expensive or less labor-intensive.

Windows that don’t close properly or have gaps could also be a sign of rot. Any gaps around the window let in moisture, which causes decay and mold, or even bugs like termites and ants that eat away at the wood.

Determine if It Needs to Be Repaired or Replaced

While replacing a frame can be more expensive than repairing it, if you don’t get all the rot out of the frame, it could spread to the rest of the frame. If more than 10% of the frame is rotten, the frame should be replaced. Or, if there is mold in any part of the frame, it needs to be replaced.

But if your frame has a few soft spots or peeling paint, repairing it and treating it with a wood stabilizer can halt the rot for a while. Small areas of decay can be removed and repaired with epoxy products too.

Vinyl Window Frames Might Be an Option

If your window frame needs to be replaced, consider a vinyl frame replacement. They last a lot longer than wood and require little maintenance. Humid climates are best for these frames, and they are more energy-efficient than wood frames. Another benefit is that the color doesn’t fade much in the hot summer sun, nor is there any paint that peels or chips, making them stay beautiful for many years.

Should you decide that this option is for you, research the best value, especially if you are working on a budget. But, because they are low-maintenance, you may find that you can spend a little more money on good-quality frames as you won’t be spending a lot on maintaining the frames.

Finally, vinyl window frames have a better seal and won’t let in moisture or drafts—a plus when you live in a wet or cold climate.

Fixing a Rotted Window Frame

1. Remove the Rotted Areas With a Chisel

Once you’ve determined that you’re repairing the window frame, you will need a chisel or flathead screwdriver to remove the rotten areas. Gouge the rotten wood out with the chisel, being careful not to take out the healthy wood. Brush away the rotten wood. Once the rotten wood is taken out and brushed away, take a hard-bristled brush to scrub away any other decayed areas.

Before you finish this step, be sure that all the rotten areas are removed before going on to the next step. Otherwise, you will need to repeat these steps when the rot moves to the sturdy wood.

If you’re taking out more wood than you’re leaving in, follow the instructions at the end of this article for replacing the frame. Remember that rot can affect the frame on both sides of the window, so you need to clear the rot on both sides. However, if the decay is only on the exterior, you won’t need to clear out the wood on the interior side.

2. Drill Holes in the Healthy Wood With a One-Fourth Inch Drill Bit

The healthy wood that remains after clearing out the rotten wood needs to be prepped before applying the epoxy. The epoxy needs to have something to hang onto in the wood, or it will likely peel off and allow moisture in again. Your repair job will be useless at that point.

To keep the epoxy in place, and keep moisture out of the frame, drill holes one inch apart with a one-fourth inch drill bit into the healthy wood. If the holes are evenly spaced out, the epoxy has a better chance to take hold to keep the frame secure and sturdy. When you’re finished, brush away any dust and debris so that the epoxy sticks better.

3. Stabilize Crumbly Wood With a Wood Hardening Product

Once you’ve cleared away as much rotten wood as possible, the next thing to do is coat the remaining wood that might be crumbling slightly with a wood hardening product. Thoroughly coat the area with a paintbrush and let dry completely. It needs to solidify before you continue repairing the frame.

The benefits of a wood hardening product include:

  • Preventing moisture from getting into the remaining healthy wood.
  • It keeps bugs like ants and termites from getting inside, which can break down the remaining wood fibers.
  • Any mold or rot that is left within the window frame will be halted, keeping your frame secure longer.

A wood stabilizer should be applied liberally to the leftover areas that were not easily removed.

4. Fill the Holes With Wood Epoxy

After the wood stabilizer has dried, mix up a batch of wood epoxy, according to the package directions. When it’s time to apply the epoxy, fill the carved-out areas to almost being overfilled with a putty knife. After every few fills, use your putty knife to flatten and spread it like you would when you’re spreading sauce on a pizza crust.

There will probably be sections, such as deeper holes where the rot was more extensive, where you need to apply a second coat of epoxy after it dries for at least 15 minutes.

Don’t worry about getting a little epoxy on the outside of the frame, as you will sand this area in the next step. Let the epoxy dry for at least 24 hours before sanding and painting.

5. Sand the Epoxy Area and Paint With an Appropriate Paint

Now that the epoxy is dry, you are free to sand the section(s) that you are repairing. Using rough-grit sandpaper, go over it in the grain’s direction to level the epoxy to the frame. Then use fine-grit sandpaper to smooth it out before painting. Remove all the dust and debris thoroughly, as you don’t want any grit under the paint, which makes your frame look unfinished or shabby.

When you’re ready to paint, choose a color that matches the existing paint or repaint the entire frame in another color. Choose the right paint for whichever side of the frame your painting. If you’re on the interior, choose paint made for interior spaces, and vice versa.

The reason you want to use exterior paint for outdoor frames is that interior paint does not stand up to extreme weather conditions. Moisture can warp or peel interior paint, so you want to prevent future rot by using the proper paint.

Again, paint with the grain of the wood to create a professional finish.

What if You Need to Replace the Frame?

Sometimes a window frame, or even part of the frame, is not worth saving. In that case, you will either need to replace the entire frame or just the part that is unsalvageable. If you’re handy with carpentry work and can replace the rotten wood sections on your own, it won’t cost you more than the materials’ cost. If you need assistance, your price could include labor from someone else installing your new frame.

You should replace the frame if the wood has completely deteriorated, or more than 10% of the frame is rotten. Another reason you would replace the frame is if it was made with tropical wood and you live in a non-tropical area.

Tropical wood is made by pressing small pieces of wood together to create a frame. Once this wood gets wet, such as on an exterior window, it rots completely and absorbs so much moisture that it rots from within. It cannot hold paint and becomes useless. If that is your frame, then it needs to be completely replaced.

Remove the Rotted Piece of Wood

If you only need to replace one or two sides of the frame, carefully remove the sections one by one. You may need a pry bar to loosen each section before removing it and carefully removing the screws. If nails hold it, use the claw end of a claw hammer to pry out the nails.

Should you come across a stubborn piece of wood, use a precise cutting tool that you can use in tight spaces. Make a series of shallow cuts across the rotten wood, stopping short of cutting the healthier wood. Once the wood has been scored, gently pry out the entire piece using a pry bar or flathead screwdriver.

Measure Each Piece Individually

When you take each piece of wood off from the frame, measure each piece so that you can cut a new section to fit the frame when you put it together. You want to measure the width, length, and thickness of each piece. Otherwise, you won’t have the same size window.

Make a note on a piece of paper on which side the part came from and which end you need to miter-saw and in which direction. That way, you will be able to put it back together the right way. If you don’t label each piece, it will take you longer to put the frame back together because you’ll be guessing which part fits where. Labeling each piece also cuts down on frustrations along the way.

Cut a Piece of New Wood for Each Piece You Remove

Using a circular saw, neatly cut new wood according to the measurements you made of the rotten wood pieces. Ensure that each piece is cut to exact specifications and that you angle each end at 45 degrees so that it fits together exactly.

Buy the right kind of wood that matches the existing frame or close to it, so all you need to do is slide it in and paint or stain. If you can’t find the exact wood to match the other wood, consider replacing the entire frame with new wood.

Fill in Any Cracks Behind the Window Frame With Caulking

Before putting the new wood pieces back on the window, seal any cracks or holes with caulking to keep new moisture from getting into the frame. It will also stop drafts, frost, and water leaking into the window frame, and potentially rot the boards in your walls. And if you’re doing all that work to replace the window frame, you certainly don’t need anything getting in the wood after you’ve finished.

Run the nozzle along the cracks and openings, creating a neat line of caulk on it. If you have larger openings, consider using spray foam insulation to seal larger holes. It will save on how much caulk you use.

Install the New Wood With Galvanized Nails

DIY experts recommend using galvanized nails to attach the wood pieces. 8D galvanized nails are the standard size and finish that are used when repairing window frames. Galvanized nails are better for exterior frames because they won’t rust in the weather conditions. Rusty nails cause stains to appear on your frame, and it could break off in time. Also, using galvanized nails in untreated wood can cause nasty stains.

Put a nail at the top and bottom of each piece to secure it. Place a nail in the center, and for particularly longer pieces, stagger the nails about 16 inches apart in pairs to make sure it holds. To give it a finished look after the frame is complete, put some putty in each of the nail holes, let dry and sand level with the frame. Or you can leave the holes there for more of a rustic look.

Paint or Stain the New Wood to Match Existing Wood

Now that your frame is complete, it’s time to paint or stain the wood. Once you’ve covered the nail holes with putty and sanded them down, sand the new wood to prime it to hold the paint or stain. Once you’ve done that, wipe it clean of any dust.

If you replaced the entire frame, you won’t need to be as careful to match the color as you would if you replaced only part of the frame.

If you repaired part of the frame, you want to match the stain or paint to the existing wood. Using paint, you’ll need to paint two to three coats on the exterior, letting each coat completely dry before adding the next layer. Then apply a topcoat.

Matching the color on an older home can be tricky, because of how faded the color is, or that color no longer exists in modern paint shops. Try to match it as best as you can or change the color completely that matches your house’s overall theme or tone. Perhaps pick up a few color sample cards at the paint or hardware store so you can compare them to the existing paint.

Conclusion

Repairing rotted window frames is a delicate process, but if the wood is too far gone, you need to replace the entire frame.

Wood that is infected with mold or rot doesn’t stop at the area you took out, especially if you don’t treat it properly first. But even with the wood stabilizers and epoxy, it still progresses throughout the entire wood frame. Eventually, you may need a full replacement on your window frames. While you can do that yourself if you’re skilled in that work, a professional can make sure your frames are installed properly.

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