I was hoping for some advice here. this is less of a DIY and more of an advice issue.
We've had 3 of our old Box Sash w/aluminum windows circa 1990 removed and replaced with uPVC Sashes. The choice for this was mainly cost.
The windows were fitted by an approved installer of the the manufacturers.
The thing is - we now have 10cm gaps between the window and the brick on the inside of the window either side of each window.
I've been told to use expanding foam to fill the gaps, but I've been advised not to by the window company, as it could make the windows bow.
Does anybody have any ideas on what to put in there instead? Should we use wooden battens to pad out the gaps?
Please let me know if you need more information and/or pictures.