I have had replacement uPVC windows fitted. They have a dark wood effect. When it is hot the windows 'move away' from the inside wall at the top and bottom corners leaving an approx. 5mm gap which lets draughts come thru. Any filler / sealant put around the inside of the frame cracks and looks unsightly
The windows have been fitted using long heavy duty screws near the corners (side and bottom fixing)
Does anyone have any ideas how to stop the windows flexing?