Uncoupling necessary?

[ryan83]

Hi everyone,

I'm just looking for some advice regarding preparing a floor with piped ufh.

It's a full ground floor. Approximately 100m2 split between seven rooms including the hallway. 1000x215 porcelain throughout. Piped ufh system. I've been advised it'll be screeded with Mapei Topchem.

I recommended installing an uncoupling membrane (probably durabase) before fixing tiles. However, the customer is asking if we could go straight on to the screed.

Would it be safe to tile straight on to this? The largest room is approximately 7x5m. Any advice would be much appreciated. Thanks.

 

[One Day]

I'd say yes, but with several big 'if's'. All of which you could forget if you use Ditra (i don't like durabase).

Yes, if it's properly commissioned.
Yes, if the floor is up to correct standards.
Yes, if residual moisture allows.
Yes, if you have perimeter and intermediary expansion joints in place.
If if if...
Too many ifs for my liking!
Ditra makes sense on a job like that.

 

[ryan83]

Thanks for the quick reply Impish.

It's the moisture that worries me most. I've read too many horror stories on here! I should be speaking to the architect and customer this week so I'll let them know my concerns and if they take my advice I'll give ditra a try!

Thanks again.

 

[Ajax123]

topcem is a rapid drying cement based screed usually mixed on site from bags. the big issue with that is the mixing and level of compaction which can be iffy at best. Given that it is cement based it will also require joints at all door thresholds and be split into maximum bay sizes of 6mx6m (that bit is probably ok. given that it is cement it is also prone to shrinkage and cracking and subject to all of Impishes "ifs" above I would advise uncoupling. Although it is not "necessary" in the strictest sense of the words it would be well advised as a precaution against potential issues later on.

 

[ryan83]

Hi, sorry for the delayed reply.

Shorty after my original post I spoke with the architect. He went away to research some of the stuff I was talking about and has come back and agreed with everything I recommended.

Thanks very much for help with this. As daft as it sounds but sometimes it's just good to know your on the right track with this sort of thing.

Cheers again.