08-01-2016, 05:07 PM
The problem is if it's cracked on the top surface filling the crack from underneath might just divert the water to some other weak or minutely fractured point, the only sure fire way is to rip the tiles off and put a proper valley in using either lead or fiber glass suitably supported, that can be done in the winter but be prepared for a bit of swearing...
Lawrence.
Lawrence.
