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Repairing Rotten Wooden Window Frames with Epoxy

Are your window frames rotting? Read how to fix it and what you need to restore them like new.

Epoxy houtrot reparatie

Wood rot is a form of wood decay that occurs when wood is exposed to moisture for a long time. This moisture allows fungi to grow in the wood, which breaks down the wood fibres and weakens the wood. This can eventually lead to serious damage.

Wood rot mainly occurs in wooden structures that are not well protected against water, such as window frames, doors, cladding and roof edges. It is important to detect and repair wood rot as soon as possible to prevent further damage. With epoxy you can easily repair the wood rot and restore the affected wood to its original state. In this article we answer the question: "How do I repair the wood rot of my window frame or door with epoxy?". We explain step by step which steps you need to take and which products you need.

How to Repair Wood Rot with Epoxy [Tutorial]

Supplies needed to repair wood rot

To repair wood rot with epoxy you will need the following products:

Tip: with the Epoxy wood rot repair kit you immediately have all the necessary materials at home to easily repair the wood rot yourself!

Stap 1. Remove the wood rot

First of all, you must thoroughly clean the rotted parts. Remove all rotten wood with a wood chisel and screwdriver until only good wood remains. After removing the rotten wood, ensure that the wood is properly cleaned and that all wood residue is removed. 

Stap 2. Impregnate the surface to be repaired with epoxy 

Mix epoxy resin with rapid hardener to impregnate the substrate. It is important to use the correct ratio, so weigh the resin and hardener accurately with a kitchen scale. Mix at least 150 grams of epoxy (100 grams of resin and 50 grams of hardener).

Apply the mixed epoxy with a small flat brush to the bare areas where the rotten wood has been removed. Always wear nitrile gloves to protect your hands. Then let the epoxy cure for 1 to 2 hours, depending on the temperature. It is important not to wait longer than 24 hours before doing the next steps to ensure a good chemical bond.

Stap 3. Fill the holes with epoxy glue (epoxy + cotton fibre) 

Now that the substrate has been impregnated, it is time to fill the holes with a mixture of epoxy resin and cotton fibre. With these two products you can easily and cheaply make a fillet. Follow the steps below to make a fillet connection:

  1. Mix the epoxy resin with the corresponding hardener in a ratio of 100:50 for approximately 3 minutes.
  2. Add cotton fibre to the mixed epoxy until a 'peanut butter consistency' is achieved.
  3. Then process the thickened epoxy as desired with a putty knife. When using universal epoxy with a fast hardener, you have a processing time of approximately 20 minutes at room temperature.   
  4. Smooth the paste as smoothly as possible and let the epoxy harden for at least 24 hours.
For this step, you can also use Variobond Epoxy Adhesive.  This glue can be easily mixed on a filler board and then applied to the surface. This option gives a smoother result, so you have to sand less. However, keep in mind that this option is about twice as expensive as making an epoxy fillet yourself. 

Step 4. Finish the window frame

After filling the holes with epoxy paste, your rotten window frame is almost repaired. Once the epoxy has completely hardened, you can start finishing the whole thing. You can do this with a sander or simply by hand. Please sand with 120-180 grit.

More information about wood rot repair

By properly implementing the above step-by-step plan, your window frame will look like new again and can last for years to come! Do you have any questions about the working method or the products used after reading this article? Feel free to contact our customer service team, via email, telephone or live chat!

Products used in this article

Choose the right product variant for your application.

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Frequently asked questions

Wood rot can be identified by discoloration, soft or crumbly areas, bubbling paint, or visible mold. A simple test is to press a screwdriver into the wood—if it goes in easily, it’s likely rotted.

Yes, you can repair wood rot yourself using epoxy. With the right materials and a clear step-by-step guide, you can restore damaged wood in a strong and lasting way.

You’ll need a universal epoxy resin with a fast hardener, combined with cotton fibers to create a strong filler paste. A complete wood rot repair kit is also available at Polyestershoppen.

Yes, it’s recommended to sand and repaint the frame after the repair. This protects the wood against moisture and extends the lifespan of the repair.

No, epoxy will not adhere properly to damp wood. Make sure the wood is completely dry before starting the repair.

A properly done epoxy repair can last for many years—often much longer than standard wood fillers.

Still have a question?

Our product specialists are happy to advise you on your project and help you choose the right products.

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