Fitting a window sill onto an uneven, non-level wall

When our kitchen was done recently the granite suppliers provided a
window sill that was the wrong size - their fault, but they left the
old one behind.
We have a window that it will fit, which currently has no sill. The
wall upon which it would sit is of lightweight concrete blocks with a
plasterboard face. Unfortunately, the horizontal surface on which the
sill would be mounted is not very well finished, and is not level. A
builder friend suggested dabbing compound and plasterboard to bring it
up to level, then laying the sill on that surface.
Is there any alternative to "dabbing compound", whatever that is? Do
I have to buy half a hundredweight just for this tiny job, or will
something else do instead? Preferably something I can buy at a Shed,
in a reasonably small quantity.
Alternatively, is there an alternative to the method proposed?
Thanks
Edward
Reply to
teddysnips
He probably meant plasterboard adhesive then plasterboard. You can buy a 25kg bag of this, which seems a lot, but it is cheap. Plasterboard is cheap too. All this is not waterproof (not that it should need to be on the inside leaf). However, I would probably run some mortar and bed the sill into that. Use 4 parts sand to 1 part cement and water. Thats the way it always used to be done. These come in 25kg bags too, but its always handy to have some sand and cement lying around ! Simon.
Reply to
sm_jamieson
Agreed - it's about a fiver a bag IIRC - it grates on me too to buy far more than you need just because you can't get small quantities, but you just remember that this is what you could easily pay for a fairly small tube of filler, which you wouldn't blink at. So just bin what you don't need.
Yes I'd go along with that too. In fact you can buy little bags of readimix mortar at B&Q etc for which relatively you pay a huge premium over the price of the raw ingedients, but may be most appropriate in your case.
David
Reply to
Lobster
[...]
Thank you both. My main reservation is irritation at using probably less than 5% of the material and chucking the rest; regardless of the cost, it's the waste I can't abide.
My preference (if indeed I could be said to have one) for the plasterboard over the mortar is that I *hate* mortar - can never get the consistency right and I worry that I'll get mortar on the face of the granite and be unable to remove it. Also, that I'll be farting around for hours trying to get the sill level (it's VERY heavy) whereas with plasterboard I can jiggle it about and pretty much guarantee to get it flat. Could I use something other than dabbing compound, though? Bonding/OneCoat etc.?
Thanks again
Edward
Reply to
teddysnips
I fitted 4 window sills over rough stone walls las night (between 10pm and 2am) with expanding foam. I decided to use the foam out of sheer knackerdness. They are solid and level! I recommend expanding foam (plus some temporary nails to hold it down.
T
Reply to
tom.harrigan
Oh, you're probably over 60 then :-) John Humphries was saying the same thing on Desert Island Discs at the weekend
Get a bag of general purpose mortar from B&Q. It's easier to use than plaster, and you can squirrel away what you don't use (preferably somewhere dry).
Reply to
Stuart Noble
Can you describe the exact method of doing this, just for the record ? Did you prop the sills and the insert the foam. etc. Simon.
Reply to
sm_jamieson
I cut the planks of wood to size, and shaped the tongue bit that goes into the groove at the back of the window using an ancient plane that I found in the garage. Once I was happy with the sills, I glued them into the window, propping them up on some bits of wood to get them level. I then tapped a couple of nails above the sills to stop them being pushed up.
After some vigorous shaking, I simply sprayed the foam under the sills as carefully and as far back as I could (one of the sills is 19" deep). I found that all the props became unnecessary once the foam was in, so I removed them. This morning the sills were really solid, and I just cut any excess foam away.
I was slightly concerned it might not work, but reassured myself that foam, and only foam is what's holding in my new windows anyway.
T
Reply to
tom.harrigan
Well probably yes, but you'll not find bonding or one-coat plaster in a smaller bag than plasterboard adhesive!
TBH I can't see why mortar would be any harder to use than plaster or plasterboard adhesive (both of would have the same potential problem of getting the consistency right).
And BTW a can of expanding foam will probably cost about the same as a bag of plasterboard adhesive; and I'd also say that it had more scope for cocking it up than the other methods...
David
Reply to
Lobster

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