Fitting a Window Cill/Sill

9 Dec 2006
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United Kingdom
I saw a post on here about fitting cills but alas I can't find it now......

I am replacing a window cill which was previously tiles on slate over a cavity wall. I have uPVC windows and have just purchased an new pine cill.

With the old tiles being removed there is no overhand on the window side of the cill i.e. the uPVC frame takes up the whole outer leaf of the cavity except in a few places where there is between 5 and 10 mm at best so there is no place to tie the back edge of the cill to the wall. This is made equally difficult/impossible with the fact that the new cill has a lip at the back so even if there was enough of an overhang there is not enough cill to secure.

1) So. does the cillhave to be attached to both leaves or just the front?

2) What is the best way of levelling the wall to take the new pine one, the bricks are fairly level but not totally - should I build up a thin layer of mortar?

3) What is the best way of securing the cill, screws, nails, adhesive (if so which one?

The cill will be painted and is in a kitchen altough not near any worksurface.

ANy advice would be hugely appreciated.



Forgot to ask about damp proofing - I was going to place some pamp course plastic underneath the window edge of the cill, is this the right thing to do?
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Hi Silverhornet,

I think you're takling about fitting a window board ? The cill is generally considered to be the outside ledge of the window / door.

If you could post a picture of the problem, you may get more replys with help ! ;)
we usually dab a 12.5mm plasterboard to the masonry using bonding compound. it will easily carry any cavity. if the dabs are moderately generous, you can tap the board perfectly level.

once set you can use a cartridge style adhesive to stick the window board down. be generous with the adhesive and use something heavy on top until set.

sticks like s*it is ideal.

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