Non-setting mastic for roof ridge tile pointing

[Steve]

'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

[Stuart Noble]

Butyl glazing compound? UV resistance might be an issue though.

[Steve]

Thanks. Might be OK, but seems designed for glass/metal/wood. Surfaces need priming -

need something that bonds well to tiles/mortar.

[Cash]

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

[Steve]

Thanks Cash. The tiles are held securely by cement and the mastic is only intended for the edges. I'll probably go with a low modulus mastic.

Steve

[wewerbob]

Just cams across this. You have to watch out for the acidity of the produc t. I think that in the old days they would use a coal-tar based product so it may not be an issue nowadays but take a look at non-setting mastic dama ge and especially how it eats copper roof flashings (about halfway down the page: view-source:

[Artic]

[e-mail] scribbled...

[Kipper at sea]

an alternative to sand/cement, to allow for slight movement.. However, I d on't know where to find it - the only non-setting mastic I can find is Plum bers' 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

It comes in a plastic bag and it looks like a mass of small white polystyre ne balls the size of pin heads mixed with some form of pink adhesive, textu re is like putty density or similar to plasterseen. It never took on to exp ensive and not very practical. Never seen it use and when asked at the merchants if they had sold any they just laughed.

[Cash]

Just thinking the same myself - bloody hell I was working for a living then, as opposed to a life of luxury in retirement now.

How time flies. LOL

Cash