For the first time installer, it can be of putting when you position a window unit into the opening to find that the fit is far from snug. Don’t panic !
Resting the window onto the wall log at the base will result in a 20-30mm gap to the left and right hand side. The gap above the window can be variable depending on how well you have settled the wall logs into their grooves.
These gaps are absolutely fine. Without them, there is a risk that the wall will get out of shape with the natural movement of the wall logs dependant upon their moisture content.
This can be particularly prevelent above the window where the movement of logs is most noticeable, this gap can vary considerably. Over the full height of the wall, the dimension can vary as much as 50mm. The window frame design incorporates the “sandwich” effect created by fixing the frame strips to the outer edges of the window frame internally and externally. It is imperative these frame strips are only attached to the window and NOT the wall logs. This will allow the window unit to move independantly of the wall maintaining the wall integrety yet allowing the wall logs to move as required.