95sqm onto screed with water based UFH - recommendations? - TilersForums.com

[Wuffles]

thats the wrong information you got there. Dural matting is ideal to use as it lets the UFH through. (as does Ditra)

Excellent information, thank you very much. He wasn't a tiler, but an engineer. I'm just trying to arm myself with knowledge.

 

[Ajax123]

Interesting point.

So we should wait longer or do you mean to say it's certainly dry enough to lay flooring on now but not actually totally dry.

Neither. I mean doa moisture test to determine if it is dry before you tile.As for the uncoupling membrane it is true to say, from a purely technical point of view, that every time you add an interface to the floor you reduce the efficiency of the heating system. However the mass of the uncoupling membrane is so low that from a practical perspective it will make negligible difference. It will cost a considerable amount more if the tiles fail due to not using it if using it would have saved that failure from happening. Its not a massive amount to spend in the general scheme.

 

[Wuffles]

I was hoping that wouldn't be required after 9 months of it being down. Is that normal?

 

[Ajax123]

Up to you. Expensive risk to take if its not dry though for the sake of a quick test. A tester costs maybe £30 that would do the job.

 

[Wuffles]

I meant is it normal for screed to not be dry enough after 9 months?

To be honest, it's not my risk, I'm not the one doing it (although it is as it's our floor, but hope you take my point). I would expect a professional to be checking dryness and giving advice if they're taking on the risk.

All I am trying to do is amass enough information to avoid the idiots that do seem to exist as in every industry.

 

[Ajax123]

No it would be perfectly reasonable to expect it to be dry after 9 months but things can get wet as well as drying out. Depends on environmental factors, floods, spills etc. never assume is my motto these days.

 

[Rizzle from the Portizzle]

No it would be perfectly reasonable to expect it to be dry after 9 months but things can get wet as well as drying out. Depends on environmental factors, floods, spills etc. never assume is my motto these days.

well said at last

 

[Ajax123]

well said at last

What do you mean "at last" ?

 

[Rizzle from the Portizzle]

What do you mean "at last" ?

well some screeds can draw in a lot of moisture from day to day be ok one day to tile but not the next depending on weather conditions and are the windows fitted ie air tight .so you should test again the day you start tilling .and all the way throught .on some screeds .

 

[Ajax123]

You mean calcium sulphate screeds I presume. All screeds do the same thing in terms of equillibrating with the atmospheric conditions. It's basic physics. At the dry stage of the screed It's often a counter intuitive process though. As the atmospheric moisture content goes up the moisture level at the screed surface actually tends to go down as the high vapour pressure in the air prevents moisture coming out of the screed. That's why you can see hygrometer readings change dramatically when the screed and the air are nearing equilibrium. We are shortly to publish a report independently derived about drying and measuring screed moisture which wil hopefully clarify a lot of the myths about drying times and such likes.