Slate pointing advice needed

[pjcm]

I have approx 2 metres square of slate to point with sand and cement. This barn conversion was finished about 8 years ago, the builder put slate tiles on to a concrete floor and pointed with sand and cement. The floor incorporates underfloor heating. The client wanted me to point this area, and against my advice left the heating on, hence the job failed. He then asked me to do the job again with the heating on the lowest it could go, again against my advice, but I did the job and it failed again. There is no problem with payment but he is adamant he does not want to turn the UFH off as I have advised due to the property being a holiday let. Are there any products on the market that i could use. Any advice would be welcome.

Thanks Paul

[Dave]

Hi Paul.

Have you added anything to the mortar to cope with the UFH..?

[pjcm]

Hi Dave
No i havent added anything to mortar to cope with ufh
Paul

[Dave]

That will be the reason it is cracking then.. Some SBR will add some flex to it.

[pjc]

i always use an adhesive grout admix in sand & cement on heated floors

[pjcm]

Thanks for the advice guys ill give them a try
Thanks again
Paul

[doug boardley]

try some hydrated lime in the pointing Paul, make your mix 5,1,1 (sand, cement, lime)