Rotten wood sills?

[Harry Bloomfield]

A job which has been creeping up on us for some years. We have timber framed windows and now some of the sills are starting to rot and need replacing. They span under the windows and have 'wings' of around 3" stretching along in front of the brick work. The later bits seem to be the main problem so far as rot is concerned.

I'm just wondering what my options are at the moment, without replacing the entire windows with new? Are the sills likely to be a separate piece to the frames? If separate I assume the frames are sat on top of the sill.

Is there likely to be a UPVC type solution to just replacing the sills?

[John Rumm]

The frames are usually separate and sat on the sill. To replace it in place normally means chopping off the projecting part and joining the new sill to the old close to the window, or trying to dig out the full depth of old sill.

You can get uPVC sills if that is what you mean. You can probably get some really nasty cover sills as well that just hide the rot!

[Cash]

John,

Unlike plastic, with timber windows that is not usually the case. the jambs are mortised into the sill and form a single unit.

Before the OP even considers chopping off the face of the old sill (or even filling with lots of plastic wood), he should very carefully inspect the area around the mortise and tenons of the jambs for rot, if there is any, then it may be better to cut out and scarf in new jamb sections and renew the sill entirely in the process.

If scarfing is needed, then in my opinion, it would be far better to replace the window - unless the frame is hardwood (such as oak) or fitted to a listed building where renewal becomes exorbitant in costs.

Agreed there. Simply use internal plastic cover sills - and yes, that really is a 'bodge' job.

Cash

[stuart noble]

Usually easy enough to chop out and replace with off the shelf softwood sills. Any tenons are likely to be shot to pieces by now so the new ones can normally be slid under the frames and bedded in Gripfil. Hardly a purist's solution but, as you've mentioned upvc, I assume that's not what you're looking for

[newshound]

Depends on the age of the building, I think. ISTR that cills were separate on a victorian house I had many years ago, and they certainly are on my current 1780's cottage (none of the current frames or cills are original).

[Harry Bloomfield]

Just looking for a solution thinking uPVC wouldn't rot so quickly for the future.