Steve wrote:
'Non-setting mastic' is sometimes recommended for pointing ridge
tiles as an alternative to sand/cement, to allow for slight
movement.. However, I don't know where to find it - the only
non-setting mastic I can find is Plumbers' Mate - obviously
unsuitable!
There are plenty of low modulus building mastics but they are not
'non-setting'. Can anyone suggest where I can get a suitable
non-setting mastic?

Thanks

Steve,

Firstly, as mastic is a sealant and not an adhesive, I wouldn't advise
using it instead of cement for ridge tiles, especially in high-wind areas -
would you use the stuff by itself to fix a door or window frame (wood or
plastic)?

Secondly, whilst "low modulus building mastic" actually sets, if the
thickness of the applied mastic is correct, then there will be sufficient
'flexibility in the bead to maintain the weatherproof seal under all
conditions - and you will only get problems if you use very thin beads of
mastic.

As for your original question, if the ridge tiles are properly packed and
fixed with the correct sand/cement/water ratio, then the tiles will still be
there even after very high winds.

Cash