Re-sealing windows to grp, Sika 291i ?

[Mandarin331]

Agreed, but do look at the data sheet to see what the recommended thickness of sealant should be. I made the mistake of thinking that the tighter I screwed it down the better the seal; not so - the whole bead seems to need to flex within itself. My layer was too thin and I think the differing expansion rates caused it to unstick and it leaked. It worked when I re-bedded the window with less enthusiastic tightening. Pardon the non-tech language!

I would suggest tightening gently until the sealant starts to squeeze out, then lealve for a couple of days to go off before finally tightening up.