The various online guides to installing uPVC windows all recommend sealing the interior edges with silicone sealant and the exterior with frame mastic. But is there any reason why I can't use a weatherproof silicone for the outside? I don't in the least mind getting mastic if it's essential, but is it? I have to confess that I don't know the essential differences between mastic and sealant.
I've installed a uPVC window into a wooden frame set into the side of my sectional concrete garage. The exterior seal will be between the uPVC and the timber, with a second bead between the timber and the concrete.
Many thanks.
Bert