Check Reveals -v- Insulation -v- New Windows

[Fraser Lamont]

Hi, I'm currently renovating a house on Skye, typically in Scotland, the window recesses have check reveals. I'm looking at getting Nordan Alu-Clad Windows. Problem - there are check reveals. I want to get rid of the old timber in the recesses, the house built mid 70's I think the original Windows (long gone) attempted  (badly) to close the cavities. I want to install the new windows the way the house was originally built - front face of window frame tight up to inner face of external block leaf. Problem would arise where window fixing straps/brackets are used. They'd either have to be bent a lot to reach the checked reveal thereby making it difficult to install Insulation on the reveal, or could I pack out the inner reveal with something like compacfoam and fix the brackets/straps through that and into the edge of the inner block leaf. We get some wild weather now an then so like the Windows to be recessed nicely. If I can use something like compacfoam, could I continue it into the Cavity to the inner face of the outer block leaf in order to close the cavity? Or do I make a timber frame to fit the inner block leaf window recess, fix that into the reveal then fix Windows to that? So many different ways of doing this, I'd really appreciate input as to what's the best course of action. TIA

[dpmiller]

I'd close the cavity with PIR/ compacfoam then use straightish brackets onto the edge of the inner leaf.

[joe90]

I fitted my windows to check reveals with angled internal cavity closure. Stainless brackets fix window to outer leaf with expanding foam tape between to make airtight. Window sat on cill protruding into the cavity a little. I made timber pieces screwed to window sides and top to screw plasterboard reveal closure too. Expanding foam over brick/window joint. Plasterboard screwed to window/timber and plasterboard adhesive to inner blockwork.

[ProDave]

I assume this is a typical Scottish timber frame build?  The frame would have gone up first, timber around the window opening on the outside forming the cavity closer, window fixed to that timber and then the outer brick or block built up to the window.

 

So the window will be a little larger than the opening in the brick.  Typical replacement window company would bodge that by making the window smaller and filling any gaps with foam and stick on bits of trim.

 

If you want to get back to original, i.e. window in original place and original size you need to do it from the inside, so strip off the plasterboard from the ingo take old window out, fit new window with straps that fix to the window frame and then the timber frame around the opening, replace plasterboard and decorate.

[Fraser Lamont]

24 minutes ago, ProDave said:

I assume this is a typical Scottish timber frame build?  The frame would have gone up first, timber around the window opening on the outside forming the cavity closer, window fixed to that timber and then the outer brick or block built up to the window.

 

So the window will be a little larger than the opening in the brick.  Typical replacement window company would bodge that by making the window smaller and filling any gaps with foam and stick on bits of trim.

 

If you want to get back to original, i.e. window in original place and original size you need to do it from the inside, so strip off the plasterboard from the ingo take old window out, fit new window with straps that fix to the window frame and then the timber frame around the opening, replace plasterboard and decorate.

Not quite, but you do know what you're talking about - my other house built in 2010 is Timber Frame, windows arrived fixed to fire stops, windows then partly sat on the timber frame and fire stop battens fixed to the cavity side face of kit panels, when the block work went up the outer reveals were rendered up to the windows. Issue I have is on my other house, it's a mid 70's house - its double block built. I have totally gutted the house, I know the windows have to be replaced from the inside but I'm a bit stuck. The top and side reveals look as though they are at least 50mm larger on the inner leaf (quite possible 50mm - 80mm). Walls are made up of 100mm Concrete Block with a 75 - 90mm Cavity. You're correct about the windows which were replaced about 30 years ago - they look as if they were bodged, and they are EVEREST Windows.

 

I want to use best practice with regards insulation and window fixing. If I use cavity closers (would need to be single flange to fit to the edge of the inner block leaf with other side butting up to inner face of outer block leaf - so check reveal closers) but that won't solve the issue where the brackets from the windows could be a couple of inches away from the edge of the inner block leaf. If I use PIR to close the cavity - butt that up to inner face of external leaf and run it like a reveal to the inside edge of the inner leaf, would I just need some sort of packing/standoff for the window straps/brackets to get good purchase on the edge of the inner leaf? Will be using NORDAN windows which are heavier than the Aluminium EVEREST windows in there at the moment and heavier than uPVC windows. Is Compacfoam designed to fill this gap as well as be used as a spacer between window and internal leaf reveal? Can a bracket fixing go through Compacfoam then into block work? My image roughly shows the gap between window strap/bracket and inner reveal. Speaking to NORDAN, they don't like people bending window brackets to fit. To add to that, though I'd want at least 25-30mm of window frame to be sealed against inner face of outer block leaf (at Top and Sides), NORDAN windows don't have a very deep frame from frame edge to the edge of the opening sash therefore they recommend using all inward opening sash's which may ruin the design. The outer reveal may prevent an outward opening sash to operate if I have 25-30mm of the frame (top and each side) hidden behind the outer leaf block. With such a shallow outer frame, it appears that NORDAN windows are designed to be fixed to the outer leaf wall. It's a nightmare!

[craig]

Your detail drawing above is a pretty standard behind the ingo fixing. Strapping back to the inner blockwork.

 

It’s more a case of using the right window for this. Nordan doesn’t sound like the right option on this occassion.