I have a GGU M04 Velux with EDW flashing fitted to a 15 degree pitch roof tiled with Marley Wessex tiles.
A new wall is going to overlap this window so it needs swapping to a GGU FK04 which is 120mm narrower.
Do I need to add a single or double new timber between the top and bottom trimmers on the side where I am filling the 120mm?
A new wall is going to overlap this window so it needs swapping to a GGU FK04 which is 120mm narrower.
Do I need to add a single or double new timber between the top and bottom trimmers on the side where I am filling the 120mm?