Windowsill Replacement in a cottage in Surrey
This house is a typical Victorian cottage with an angled bay window on the front elevation. These bay windowsills have rotted due to water penetrating through the cracked and flaking paint on the exterior. If the exterior paintwork on sash windows is not maintained properly, slowly the rain water will soak in to the timber and cause major wet rot problems, first the windowsills will start to rot, this rot then spreads to the lower parts of the box frame and then up into the lower sash itself. If the rotten timber is not addressed the rain water will soak through the windowsill and into the interior plasterwork beneath the sill, the plasterwork then blows and starts to fall off.
What to look for
- A tell tale sign that a windowsill is rotting is a discolouration of the plasterwork on the interior plaster beneath the windowsill, usually a brown watermark
- Inspect the exterior windowsill in the corners where the windowsill meets the box frame, push a pointed object such as a screwdriver into the wood, if the wood feels soft the windowsill is starting to rot
How to fix a rotten windowsill
We often find that quick fix repairs have been made to try and repair sash windowsills using filler, the trouble with filler is that the repair looks good for a while but when the weather changes and the wood starts to expand and contract the filler does not, this results in the timber pulling away from the filler and then paint cracks, rain water gets into the cracks and we are back to square one.
First we cut out the rotten windowsill and the lower portions of the box frame then we rebuild the whole lower portion of boxframe and fit a new hardwood windowsill.
On this job once the windowsills were replaced the owner chose to have new double glazed sashes fitted to the existing frames.
Take a look at the photos on this page to see how we repair a rotten sash windowsill.