How soon before I can lay tiles on a screed floor with UFH? - Tile Advice

[macapaca]

I was hoping someone may be able to advise me on when we can lay down our tiles.
We poured a 60mm screed on February 14th with wet underfloor heating set inside.
After a waiting several weeks we tuned on the heating and have been waiting for the floor to be dry enough to lay down the ceramic tiles.
The moisture is still at about 8% and I am wanting to know if we can now lay down the tiles?
Does the floor have to be totally dry for the adhesive to set?
Any advise will be much appreciated.

 

[Darren Wake]

Hi , if you were to use bal flexbone matting you can commence immediately, alternatively bal fast track green screed.

 

[Flintstone]

The most important question here is what is the screed ?

 

[Darren Wake]

The most important question here is what is the screed ?

Fair comment , maybe jumped the gun. I was under the impression bal flexbone matting could be used on any screed.

 

[Dumbo]

Fair comment , maybe jumped the gun. I was under the impression bal flexbone matting could be used on any screed.

Definitely with an anhydrate screed using flexbone it still needs to below a certain moisture reading which I believe but check this is still about 85% rh

 

[Old Mod]

With anhydride RH must be below 85%
Sand and cement 75% RH

What method are you using to test moisture content.

What is the floor material that you intend using?

 

[macapaca]

It is anhydrate screed. I am using a moisture meter that I have for testing wooden logs (I think this may not be the right type of meter)
Anyway it has gone down to about 10% and doesn't seem to go below that so I am thinking that this is the lowest it will go. The floor has been hot for weeks now so I am thinking it has to be good to tile now. I am using ceramic Legend wood effect tiles.

 

[Old Mod]

Fair comment , maybe jumped the gun. I was under the impression bal flexbone matting could be used on any screed.

Can’t say for sure as flexbone is not a product I can use for technical reasons.
However, even tho ditra 25 can be used as a vapour barrier. It’s not suitable to fast track anhydride screeds.
So you would need to check technical specs to be sure.

All screeds dry at a similar rate without being force dried, that is to say, 1mm per day for first 40mm and 1mm every two days over 40mm.

If your ufh has been running for some considerable time, there’s ever chance it’ll be dry by now, needs a new moisture check done.

Firstly you must use a Hair hygrometer moisture metre or carbide bomb test to ensure a correct measurement.
Any other type of metre is u reliable (mostly) and one for the incorrect material is definitely a no no.
A lot of adhesive companies with moisture check for free for you is you’re using their product.

 

[Flintstone]

What are you plans regarding sanding the screed ? As above you need to use the correct moisture tester to be certain. Ceramic tiles ? Personally I would be very weary of fitting ceramic tiles on a heated screed

 

[macapaca]

What are you plans regarding sanding the screed ? As above you need to use the correct moisture tester to be certain. Ceramic tiles ? Personally I would be very weary of fitting ceramic tiles on a heated screed

The floor was sanded about a month ago. What type of tiles do you feel happy about laying on a heated screed floor?
Thanks

 

[Flintstone]

Porcelain, or stone with an uncoupling membrane.

 

[macapaca]

I double checked and the tiles are porcelain

 

[Darren Wake]

Definitely with an anhydrate screed using flexbone it still needs to below a certain moisture reading which I believe but check this is still about 85% rh

What are the technical reasons you cannot use bal flexbone matting, curious to know.

 

[macapaca]

Because it seems like it may be unnecessary. I think I have just been using the wrong type of meter and the floor is already dry enough to lay directly.

 

[Old Mod]

Because it seems like it may be unnecessary. I think I have just been using the wrong type of meter and the floor is already dry enough to lay directly.

Don’t assume anything, thinking the floor is dry enough, is not good enough.
If you’re making a large investment in your floor, and your intention is to stay there a while, why risk it?
As I said, most reputable adhesive companies will do it free of charge.
Why take a chance?
On occasion, because of extenuating circumstances, floors can take an age to dry, especially Anhydride, they are like a sponge, hence they’re not recommended for wet areas without a high level of tanking to protect them.