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Repair Rotten Sash Window Sill

Repair Rotten Sash Window Sill

Often bearing the brunt of the British weather, sash window sills need an experienced hand to repair properly.

One of the main sections of timber to deteriorate within a sash window is the external sill, but this can be easily combated if they are maintained properly.
The sill gets the brunt of the weather and this can, dependent on the elevation, decoration regime and whether the window is operational, result in the sill absorbing rainwater, thus leading to rot setting in.

It is often misunderstood that the north facing windows would be the worst affected because of the lack of sun. In fact the opposite is true; generally it is the south facing windows where early deterioration occurs due to sunlight cracking the paint, allowing moisture to penetrate the sill.

The Ventrolla free, no-obligation survey carried out produces a window condition report which identifies whether a sill repair or replacement is required.
Dependant upon the location and amount of rot, sills can be repaired by removing the rotten timber and using Ventrolla’s special wood stabiliser and unique two-part epoxy resin; the Ventrolla VR90 Wood Repair System.

"Our experience with Ventrolla, from start to finish, has been outstanding. The windows look superb and absolutely deliver what was promised in terms of performance. The installation was very efficient and neat; and done with the utmost professionalism and engagement. Well done, guys, and thanks."

Should a repair not be possible due to the location or extent of the rot then a replacement sill is advised along with the outer lower box section (usually up to 300mm up the frame). This ensures that any rot in the outer cheeks or pulley stiles is also removed.

Alternative methods, for instance splicing front edges onto sills or removing only the sill from the stile, creates a weather joint which can lead to early failure of the remaining part of the existing sill. Subsequent damage to the internal plasterwork may weaken the box by removing the lower frame joints and will inevitably result in escalating costs.

Replacing the complete sill and outer lower box assembly ensures any rot is removed completely and that new, well-sealed joints are constructed. This guarantees the box frame retains its strength and integrity, and that no gaps are left between the sill and the frame, thus preventing water ingress.

Any exposed timber is then primed ready for painting by others.