Why Rotten timber in sash windows should be addressed and repaired as soon as the rot has been discovered.
If rotten timber is just left to carry on rotting in a sash window it can start to cause a whole host of problems not only to the rest of the sash window but can lead to blowing of the interior plasterwork and in some cases if left for quite some time it can lead to the erosion of the exterior brickwork causing structural issues.
When a windowsill starts to rot the whole windowsill and lower portions of the box frame should be replaced, the replacement isolates the moisture from the existing rotten timber and ensures no further repairs will be needed in the near future, it is common practise for builders, decorators or a handyman to put filler on top of rotten timber to cover up the damage but filler will only last for a short while before another repair is needed, full replacement of the windowsill and lower box frames is recommended.
A lower sash is the lower sliding part of the window and usually starts to rot from its bottom rail, once wet rot moisture has fully penetrated the bottom rail and stiles it is recommended that the lower sash should be fully replaced.
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