Repair Rotten Window Frames



Rotting wood in your window frames can be a pain in the neck – and in the pocket. To remove and replace a window is a major expense. So we’ve made this movie to show you a great repair which will look good, last for many years and is quite cheap to do. It’s quite quick to do yourself, no more than a couple of hours. So have a look at the movie, send a link to all of your friends so that they can see this tip too.

Wooden windows often rot in the corners, where water gathers after rain.

We’ll show you a repair which is quite easy, will save you a bundle of money and extend the life of the window frame for many years.

Begin by removing all of the wood rot. We generally use a chisel for this purpose, although there are many tools that will do the job. Use a rubber mallet if necessary. The rubber mallet has a soft sound that makes the job more pleasant, as opposed to the metal jarring sound that a hammer would make. When you work on the part of the window frame that holds the glass, take great care not to crack the glass.

We’re going to fill the hole with car body filler, exactly the same stuff that would be used to fill dents on a car. It comes in two parts, the filler and the hardener. The filler will not harden until a catalyst, which is commonly called the hardener, is added to it. Once cured, the body filler becomes rock hard and will last for many years.

Mix up a batch of filler according to the manufacturer’s instructions. This is usually about 4 or 5 drops of hardener to one desert spoon of filler. Mix it well and trowel it into the gap. A putty knife used with a scraper works well. You may discover a better tool. If you do, be sure to let us know and we’ll share it with our viewers.

This hole in the frame is big and will take 6 or 7 batches of filler to fill. If you need more support for the filler, insert a few nails or screws into the wood that you are filling. Build up the filler from the bottom of the hole, pushing the filler into the wood to form a good bond. After each layer, shape the profile if necessary. The filler uses a chemical process to dry and will harden suddenly after 4 or 5 minutes. It has a cheesy consistency at this stage and should be shaped before it gets too hard. After half an hour it will be very hard. We’re using a chisel and a utility knife to shape the filler. A small power sander will also work well. Choose a tool to suit your conditions.

After a good sanding with 100 grit sandpaper, the window frame can be finished. Topcoats can be applied directly to the filler. We’re using Plascon Wall and All for the windows. Wall and All covers well on almost any surface. It’s water based, so clean-up is easy and it withstands direct sunlight well.

Our trick of painting onto the glass has a few interesting advantages and makes painting window edges much faster than normal. The paint fills the gaps between the glass and the putty to create an extra seal. After an hour the paint is touch dry and we slide a window scraper across the edges. We get a great edge and the window painting is fast. This is a great technique for windows that have a lot of small panes.

This job has cost less than R200 and has taken 3 hours in total. It’s saved at least R3000 in the cost of buying a new window, having it fitted, and having it painted.