I had a problem in my villa in Marbella where I have a 220m² terrace set above a four bedroom basement. When it rained I was getting water ingress through the bedroom ceilings in eight different points.
To lift the terrace and relay, I was quoted €22k. I spoke to Abacus who recommended DO-IT-ALL their multi-purpose clear sealer.
I wasn’t totally convinced, but gave the terrace two coats during the summer, paying particular attention to the grouting ‘cracks’. Since then I haven’t had a problem, it was bone dry all last winter and I will continue to apply a coat as a preventative measure every year.
Really does what it says on the tin!