Window sill/board preparations

[Craig-SM]

I'm still on with the never ended kitchen project. We have new windows on order and wanting to replace the inner window sill/board with 30mm polished slate prior to the window fitters arriving. Removed the facia boards the previous owners used as sills and the orignal wooden ones they'd been glued onto.

The pics below show the hidden mess. It looks like breeze block inner with brick outer filled with some kind of insulation fluff. I'm assuming, and looking for advice too if wrong, that I need to push the insulation down, partially fill with expanding foam and then level off to the top of the outer brickwork with cement. If not please put me on the right path.

BTW I'm keeping the tiles so hopefully don't need to remove.

 

[Pigeon_Droppings2]

The approach I've been using is to just put a thin tile backer board over the brick/block. The tile backer has an insulation layer and that helps reduce cold bridging (from outer to inner skin).

If you are careful you can trim off the plaster snots and keep the tiles in place...just match the thickness needed and drop it in...pu foam adhesive to hold it down.

 

[gaz1]

that insulation is blown in type

its up to you if you get tile backer board if you tile the window bottom my preference is plastic window bottom

what is your depth and width if you dont mind me asking ?

as i can check what i have in as it looks like it might fit yours if you want plastic and its 1/2-3/4 thick

 

[Craig-SM]

that insulation is blown in type

its up to you if you get tile backer board if you tile the window bottom my preference is plastic window bottom

what is your depth and width if you dont mind me asking ?

as i can check what i have in as it looks like it might fit yours if you want plastic and its 1/2-3/4 thick

We are having custom pieces of polished 30mm thick slate 19cm wide and 120 & 155 long but thanks for the offer.

 

[Craig-SM]

The approach I've been using is to just put a thin tile backer board over the brick/block. The tile backer has an insulation layer and that helps reduce cold bridging (from outer to inner skin).

If you are careful you can trim off the plaster snots and keep the tiles in place...just match the thickness needed and drop it in...pu foam adhesive to hold it down.

That seem a lot easier than I was thinking of doing

 

[Smallfry]

Check than none of those thermalite blocks touch the outer wall, as this will make a cold bridge and also encourage damp in extreme weather coditions.

30mm slate will be heavy. If it were mine, I would clean off the plaster lumps, then replace with a sharp sand mortar mix, but leave a two inch gap between this and the outer leaf/window frame. Could make a spacer out of Celotex. This will give the slate a firm and stable base to sit on, assisted by adhesive.

 

[Craig-SM]

Check than none of those thermalite blocks touch the outer wall, as this will make a cold bridge and also encourage damp in extreme weather coditions.

30mm slate will be heavy. If it were mine, I would clean off the plaster lumps, then replace with a sharp sand mortar mix, but leave a two inch gap between this and the outer leaf/window frame. Could make a spacer out of Celotex. This will give the slate a firm and stable base to sit on, assisted by adhesive.

The inner brickwork isn't level and has chunks missing from it so will level off and fill with mortar to create a firm base for the backer board to adhere to. The block don't touch the outer wall but I think I will use your suggestion too and the top of the gap with some celotex, again to create a good base for the backer board but also something for the mortar to butt up to.

 

[bricol]

I think I might leave it until after the window is fitted - you can seal to the frame as you want, and carefully too. Yer average window fitter wants the old one out, the new one in, as quick as possible, and off home.

I was dead impressed with the work ethic of the two who fitted all mine last year, the speed and efficiency of how they worked together. But fine detail finishing . .

 

[addjunkie]

I think I might leave it until after the window is fitted - you can seal to the frame as you want, and carefully too. Yer average window fitter wants the old one out, the new one in, as quick as possible, and off home.

I was dead impressed with the work ethic of the two who fitted all mine last year, the speed and efficiency of how they worked together. But fine detail finishing . .

I too would leave till after the window is fitted. Thats a fairly polite way of describing window fitters