How do you install granite window sills on Styrodur boards? In my case, the window sills in the concrete basement are made of Styrodur, since Styrodur was used as the formwork. Are granite window sills now installed on Styrodur in a mortar layer or with installation foam?
We have soffit that is backed with Styrodur. Like all other window sills, it is also in a mortar layer.
Before applying the Styrodur mortar, sand it again lightly (60 grit sanding mesh or similar) and then it will adhere.