Wooden Frame on Inside of Window Rotting

Has there been a ‘suspicious’ change of appearance of your window frame?


Some of the initial indicators that you window joinery could be leaking, is the corners of the sill start to discolor and actually begin to look moisture damaged.

What could be causing this?

There are a few different possibilites:

1) After doing many thousand home inspections, we have determined that is 50% of the cases the window isn’t actually leaking at all! It’s a condensation problem where beads of water naturally fall down onto the timber frame of the window and it begins rotting. This is especially the case where the windows are old and don’t have little outlet holes along the bottom to let the water out. (Or no condensation channel)

2) Water is actually getting in the sides of the frame on the outside, and tracking down the sides of the frame and dropping off at the low point (corner) of the window. This is all happening behind the wall and you won’t actually know it’s happening until you visually see the moisture damage to the wood. If you have an issue like this, make sure you take a good look around the frame on the outside to make sure it’s all sealed up correctly.

3) Window mitres. These are the very fine 45 degree angles you see in the corners of the window where each side of the joinery meet. The seal on these mitres can ‘unseal’ real quick because with movement of a home the shear leverage breaks the seal. If there is a air pressure difference between the inside and outside of your home, and the raining is driving into a particular window under heavy wind, then water can literally get sucked through and into your wall under the window.

In some cases, if you bend down so your eye level is the same as the mitres, you can see light through the joinery!