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Sash window cill repair

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marcus

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I need to cut out and replace the front part of a sash window cill. What's the best method to cut it our?

Should I aim just to cut it across square and screw/glue a replacement piece on, or is more cunningness required?

Thanks.
 

owen

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I need to cut out and replace the front part of a sash window cill. What's the best method to cut it our?

Should I aim just to cut it across square and screw/glue a replacement piece on, or is more cunningness required?

Thanks.
Depends how bad it is, you usually find that the underneath of the cill is in a lot worse condition than it looks from the top so you might end up replacing the whole lot. In the past I have used accoya to make like a cover cill to go over the existing if the windows don't open.
 

AndyT

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I've done this successfully with a second-best chisel but if you have an oscillating multi-tool it's the sort of job they are good at.

I'd advise you to make one or both ends of the hole and the patch angled, rather than at 90 degrees. That way, you can hammer the patch in until it's tight end to end. Then, after the glue has dried, you can chisel back the surfaces to make them flush.
 

Oddbod70

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An old, but vaguely sharp saw and old vaguely sharp chisel to cut out an elongated wedge (apparently called a trapezoidal isosceles - try saying that after a few) containing the rotten part.

Paint on several of coats of wood preservative.

Cut a piece to match, its OK to make it slightly thicker and deeper by a couple of mm. Don't forget the drip groove. Paint the end grain with several coats of preservative.

Glue in place (use two part wood filler if you've really made a hash of the mating faces) and screw in into place.

Fill the screw holes with the wood filler (work quick), belt sand the new bit flat and smooth. Paint with several coats of preservative.

Paint as required, stand back, admire, and bask in the admiration of your other half.

That's how I do it anyway :)
 

marcus

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Thanks both, ready to get on with it now :)
 

Ollie78

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In short NO.
In a bit longer. The pulley lining is fixed into the cill by means sitting in a slot cut in the cill, similarly the inner and outer cheek are cut into it front and back.
If you cut the cill out between the pulley linings and replace it with a square ended bit of timber it WILL fail, always. This is known as "slipping" a cill.
You should replace the entire cill.
You will lose all the structural integrity of the box, nothing to stop the two sides wandering about.
Cut out the pulley lining above the pockets, cut out the rotten bit of outer cheek either side you can leave the inner cheek in there but cut through all nails with recip saw, cut the cill in the middle and pull the centre out (do not forget the window board will be nailed to it so cut those nails too ).
Replicate all the timber you removed and put it all back using a decent epoxy (timbabuild or windowcare etc), the cill will fit once you have cut the ends for the inner and outer cheek (twist it in) then assemble all the other bits.

Note I have assumed a proper box sash window, with weights and pulleys if its a spiral balance window it won`t be made like this.

Ollie
 

Oddbod70

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Worked for me well enough. 8 years and still fine. If/when it does fail I'll be OK with the time spent/time gained equation.
 

Davy

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Have fitted hundreds of cills over the years You really should do the complete thing as the outside facing, pulley style and parting bead will be on the way out also You will have a casement that is as good as new after that
 
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