We live in a fairly new build. We've recently noticed the UPVC double glazed window sashes were jigged off centre in all the upstairs egress windows causing drafts as the hinge side (side opening). On the hinge side the sahes overlap the frame by 1mm at worst to 3mm at best where the sashes were jigged off centre.

I have also measured the the o/all sash sizes and the frame openings and the sashes are 10mm (o/all) bigger than the opening that if jigged centrally would only give a 5mm overlap/side. The profile is Duraflex and according to their fabrication details it should be 15mm (o/all) bigger than the opening giving 7.5mm/side overlap. According to Duraflex the fabrication tolerance is up to 2.5mm smaller than the fabrication details (even though there is no reference to this).

Does anyone have any experience regarding if a 5mm overlap would be sufficient for the sahes to seal successfully against the co-extruded Q-lon gasket? Also with regards to the friction stay hinges that a Duraflex has a 13.5mm stack Height but if the sash is 2.5mm undersize surely this would now be 16mm?? Would this have any adverse affects on the hinges if the 13mm stack Height hinges have been installed as I presume they would have been.

Thank you in advance for any advice given.

Posted By: RobLUpvc sash windows are unusual

I think Paul is using sashes [correctly] to mean the movable part of a window, not to indicate a type. 'the hinge side (side opening)' is a big clue

edit: to say I'm wrong about the definition of the sash. It doesn't have to be movable, it's just the bit that contains the glass. See e.g. https://www.stanekwindows.com/what-is-a-window-sash-and-why-is-it-important.aspx And the window type you are thinking of is a 'sliding sash' window, which makes sense.

From Duraflex casement pdf, it looks like the external casement overlap has a rubber seal insert, I assume that's what you mean by the Q-Lon gasket. That would need to make good contact with the frame. I would guess if it doesn't then the casements are incorrectly sized.
The gap between the frame and the casement should have been designed to take the appropriate friction hinge stack whilst still maintaining that appropriate seal contact all round.

Thank you all for your advice.