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How to Fix or Replace Rotted Wood Around a Window

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Windows are efficient ways of letting in natural light and air into a building while also increasing the aesthetics of the building. Like most parts of a building, windows can get damaged. Wooden windows are more prone to damage, especially those caused by moisture.

If you live in a wet area with a lot of humidity, your windows are susceptible to rot. One of the first areas to start showing signs of rot is the window frame. Windows made from other materials like metal, vinyl, and aluminum are more durable and will not rot. However, many houses, especially older ones, make use of wooden windows and frames.

One thing you should be aware of is that when moisture damages a wooden window, it is not always visible at first. Oftentimes, it will remain that way till it has affected a huge part of the window. To get ahead of the problem and discover the damage on time, you can press a screwdriver into a window.

A spongy feel indicates the presence of moisture in that part of the window. Usually, the lower parts of windows not protected by any overhang are the most susceptible to rot.

Typically, when a window rots, depending on when you discover it and the level of damage, you’re presented with two repair options; you can’t remove the rotted part and fill it with epoxy or completely replace the damaged part. A complete replacement is done for bigger damages, whereas filling with epoxy will work for smaller rot.

These two methods of rotted window repair can be done easily with little experience once you have a proper guide to follow. What we’ll be doing in this piece is to provide that guide that’ll show you how to how to replace rotted wood around window.

What Causes Window Rot?

What Causes Window Rot?

Before you go ahead to see how to fix window rot, it’ll be beneficial to know why windows rot. Knowing some of the causes of window rot will help you guess places of possible damage in your home.

The presence of fungi and moisture causes window rot. Moisture helps the fungi to grow and spread as it damages the wood structure. These two factors are the underlying causes of window rot. Moisture can get to your window, especially the lower parts, and seep into the edges.

Steps to Fix or Replace Rotten Window

Steps to Fix or Replace Rotten Window

Do you want to get that rotten part of your wooden window fixed or replaced? There are two major ways to do this, depending on the level of damage in the window. For smaller rot, you can use the first method.

Method 1: How to Fix Rotted Window?

Early detection will allow you to fix the window rot instead of outright replacement. Checking out for chipped-off corners or spongy wood will allow you to spot the rot before it becomes quite visible. When you notice small damage, you can fix it thereby saving money, time, and energy in the process.

Materials Needed

  • Epoxy wood filler
  • Paintbrush
  • Wood paint
  • Waterproof wood hardener
  • Drill
  • Chisel
  • Sandpapers
  • Epoxy consolidant

Step by Step to Fixing Rotten Window

Here’s how to fix it:

  1. Determine the Level of Damage
Determine the Level of Damage
  • Check your windows by applying pressure with a screwdriver and looking out for a soft, spongy feel. This indicates the presence of moisture in any part of the wooden window.
  • Probe every 3 inches to determine the extent of damage the rot has gone into your window. Oftentimes, it is difficult to determine the level of damage using the eye test till the moisture has completely rotten a whole section.
  • By probing, you’re taking the initiative and trying to nip it before it spreads. If you notice the moisture in only a small part of the window, say less than 20% of the window, fixing the damage with epoxy wood filler would be the best option.
  1. Scrape Off the Rotted Part with a Chisel
  • Use a chisel or a flathead screwdriver to scrape off the rotted parts. Because of the moisture and rot, it’ll be easy to remove the damaged parts.
  • Dip the tool inside the damaged area and drag it gently to remove the rot. You want to carefully do this so you do not scrape off the good area.
  • Ensure to remove as much rot as you can so you do not leave too much in the wood that can continue spreading even after repairs have been done.
  • After the scraping, you’ll know for sure if it requires fixing or replacement. If the damage is more than first thought, you may have to replace it.
  1. Mix And Apply the Epoxy Filler
Mix And Apply the Epoxy Filler
  • Mix the epoxy by following the manufacturer’s instructions. Mix on tarp or plexiglass to prevent the epoxy from sticking to the surface. Usually, 2 bonding materials need to be mixed in equal measures.
  • Cover the hole with epoxy consolidant and allow it to dry for some minutes. This solidifies the weak area so the filler can work better.
  • Apply the epoxy wood filler into the hole till it fills up. Make sure to apply the epoxy within 30 minutes of mixing it, to not let it dry. Mold it into the shape of the window so that it blends in when finished.
  • Allow the epoxy filler to dry for about 4 hours; however, leaving it for 24 hours is best before moving to the next step.
  1. Sand the Epoxy
  • Using coarse sandpaper, sand the dried epoxy down. 80-grit sandpaper is a good way to start to remove excess filler before you then switch to smoother sandpaper, like the 120-grit, for a smoother surface and to get a level surface with the wood.
  • Sand it so you can get the shape of the window. Use a vacuum cleaner to clear loose dust particles after sanding so the area is clean.
  1. Paint
  • The paint is to improve the aesthetics of the window as the epoxy color and the rest of the window are usually different. Select the color of the window or a different color if you’re looking to change the window color entirely.
  • Using a paintbrush, rub paint over the epoxy-filled area. Do at least two coats over the epoxy area and surrounding to create an even and sharp look. If the paint in the other parts of the wood has faded, you may want to go over the rest with a single layer of paint to bring back its shine.

Method 2: How to Replace Rotted Window?

How to Replace Rotted Window?

Larger rotted areas in your window will require outright replacement instead of fixing with epoxy. Fixing a large area with epoxy will be expensive and will provide poor structural strength for your window.

Typically, when moisture is allowed unchecked for a long time, the wood will be badly damaged and will require the replacement of the rotted pieces.

Materials Needed

  • Saw (table saw or circular saw)
  • Mallet or prybar
  • Replacement lumber
  • Wood potty
  • Drill or hammer
  • Screws or nails
  • Tape measure
  • Paint or primer
  • Caulk

Steps to Replace Rotted Window

If you want to replace wood pieces that have rotted on your window, here’s a simple guide to do it:

  1. Mark the Damaged Area and Remove Rotted Trim
  • First, determine which parts of the window have rotted by using the probing method. Usually, if it requires replacing, the damage will be visible at the point as it is extensive.
  • Mark the pieces that have been badly damaged for removal.
  • Using your pry bar or mallet and hammer, you can remove the damaged pieces. While fixing the rotted window, you only need to scrape off the rot.
  • Here, you may want to remove the whole piece that has been damaged. This is because the area is larger. Put your pry bar under the surface of the piece marked for removal and then pull to remove it.
  1. Clean the Area and Measure the Gap
  • Clean the area to remove rotted particles and prevent them from spreading. Remove loose nails and debris that can obstruct the replacement of that piece.
  • Observe the area under the gap to ensure it is not affected by the rot. Check the sheathing under the removed piece for any breaks. If any, repair it by sealing it with caulk and pressing it down.
  • Use your tape measure to assess the gap created by the removed window piece. You can also measure the removed piece if it is still intact.
  • This measurement will be used to create the replacement lumber for the window. Make sure to take all measurements if the gap is in different sections to get every replacement measurement needed.
  1. Cut the Wood
  • Using your saw, cut out the replacement pieces by following the measurements gotten from the gap in the window. Ensure you make accurate measurements so that the pieces fit in perfectly. This will create a seamless finish at the end.
  • Make sure to wear protective gear, especially a dust mask, as dust particles will be up in the air while cutting the lumber. Use durable hardwood so you can get a long-lasting window.
  1. Check the Fit
  • After cutting the wood, place the piece close to the gap the see if it fits. If you got your measurements correctly, they should fit flush inside the gap.
  • However, if it is too big for the gap, you can use the saw to chop off the excess part. If your piece is too small, you can fill up the remaining with a wood filler like epoxy or potty.
  1. Secure the Piece
  • If it fits snuggly, you can go ahead to secure the replacement part using nails and a hammer or drill. A drill bit and screws are the more convenient method as you don’t need to apply extra pressure and risk damaging your new window replacement piece. However, using a hammer and nails is still an effective way of fastening the piece.
  1. Add Primer And Paint
  • Use the caulk to fill up gaps between the pieces and remove possible water holes. The caulk makes it difficult for water to seep in and damage the window.
  • Finally, add primer and paint to the replacement wood to secure it and improve its aesthetics. These additions will seal the wood and prevent water from entering, which is the main cause of wood rot.
  • The paint helps to blend the new piece into the whole window set-up. Use matching paint with the rest of the window and go over the new part. Do 2 to 3 layers to properly get the paint in and bring out the shine. Allow the paint to dry for some hours.

How to Prevent Windows From Rotting?

If you want to save yourself, time and resources, it’ll be best to prevent the rot from happening. There are several ways to do this.

1. By Priming, Painting, And Waterproofing

These three go hand-in-hand as they protect the wood from rotting. First, you need to apply several layers of primer on the surface of the wood, ensuring that each later dries before you apply the next. The primer seals the wood spores and helps the paint stick.

Adding latex paint that blocks water from entering the wood while remaining weather resistant. Apply at least 2 layers to the wood to improve its effectiveness. Add several layers of a waterproof wood sealer to completely block water from entering the wood.

2. Seal Leaks And Cracks

Check for leaks and cracks around the window, its frame and sil. These cracks pave the way for water to enter the wood and damage it. Early detection and repair will prevent any damage. Perform routine checks and seal off any cracks or leaks with caulks or potty.

3. Use Fungicides

Use fungicides to keep fungi that cause wood rot. Spray the fungicide as recommended and kill off the fungi before it starts to work with moisture to cause rot.


You do not have to replace the whole window when you notice rot in a particular part. You can repair or replace the damaged part and get your window looking new in simple steps.

However, the majority of what you can do relies upon early detection, so you need to understand how to identify wood rot even before it spreads. The earlier, the better is paramount here. Preventive measures will also save you the hassle of trying to repair the window, so invest in these practices.