Reducing window opening size...

[Mulberry View]

Is there a decent way to reduce a window opening in a Nudura build (Concrete is in already), without risking integrity and air-tightness?

 

One of our window openings is a little bit too big to be able to be configured how we want. Ideally, we need to pull the sides in by about 50mm each side and the bottom up by 150mm.

 

In doing so, we can keep with the Triple Glazed, Top-Hung Outward opening window that we prefer as opposed to a Tilt & Turn window, which we're not very keen on.

[Redbeard]

How about rigid EWI which you can fix to the concrete and then render over?

[Mulberry View]

  On 03/01/2025 at 21:15, Redbeard said:

How about rigid EWI which you can fix to the concrete and then render over?

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This is just in the window openings. The existing EPS can stay (or not). It won't need to be rendered as it'll be part of the window detailing.

[Mulberry View]

Any further input on this? If I have to add, say, 100mm of material to an opening to reduce it's size, is 150mm of EPS too much to screw through to attach the windows? I could remove the original EPS closer and replace it with timber, before adding the additional EPS over the top, that would give a nice fixing, any implications in this?

[JohnMo]

Use compacfoam. Attach compacfoam to opening adhesive and screw, into concrete.

 

Then attach window to compacfoam.

[Russell griffiths]

I made 4 of my windows smaller on a nudura build, spray foam eps 100 directly to the reveals. 
dont overcomplicate this, just continue your airtight strategy over the extended piece of eps, so wider tape or extend the liquid membrane out further. 
windows will just need longer screws in the straps.