TILING ON CONCRETE SCREED

[nalla]

Hi lads, customer has a new build with standard concrete floor which has been down for 4 months (no problem) they have also got underfloor heating, (hot water pipe system) the screed on top of water pipes has only been layed for 4 weeks and they are phoning me all the time saying it is ready for tiling, i have explained to them that the floor will take 2 months to dry and ready for tiling (especially this time of the year) otherwise the floor tiles could crack with any hidded moisture, i understand that they are keen to get the job finished but i would walk away from the job rather than them pressureize me into starting too soon. What's your views on this??? thank's in advance for any replies.

 

[Dumbo]

Get a moisture metre and show them its not ready .

 

[Time's Ran Out]

1) Has the UFH been commissioned ?
2) How thick is the screed?
3) You could use a decoupling membrane to hasten the process.

 

[nalla]

1) Has the UFH been commissioned ?
2) How thick is the screed?
3) You could use a decoupling membrane to hasten the process.

The ufh has not been commissioned because it is a free standing water tank which will be on top of the floor tiles, as for the thickness of the screed i don't really know because i was on another job when they had it laid, i will ask them for the builders number and ask him myself but they told me it was the standard thickness for the job.

 

[Time's Ran Out]

Ok you need to know the thickness of the screed and allow 1mm per day for drying from day of drop.
Unless the UFH has been commissioned I wouldn’t lay any tiles without a decoupling membrane.
Has the UFH been pressure tested?

 

[Sean Kelly]

Nalla, the guidelines for screed and wet UFH are:
Lay screed and wait at least 3 weeks for movement and shrinkage.
Switch on UFH at a rate of 5degs every 24 hours upto max operating temp.
Maintain max temp for 3 days then turn off.
Wait 48 hours then tile.

However, if you are using a natural stone tile then use Ditra.
If using Porcelain then it should be fine to tile without Ditra.

Before you do the above, I suggest you find a plastic bucket or a sheet of plastic with a tile on top and place it on the floor for 24 hours. If after 24 hours there is moisture then it is not safe to do any of the above.

I went to a house just before Xmas and the owners said the screed was dry. I put a plastic paint tub on the floor and picked it up 15mins later. There was a wet patch on the screed in the shape of the bottom of the bucket!

 

[nalla]

Ok you need to know the thickness of the screed and allow 1mm per day for drying from day of drop.
Unless the UFH has been commissioned I wouldn’t lay any tiles without a decoupling membrane.
Has the UFH been pressure tested?

I've been in touch with the person who laid the screed and he told me that the screed he used goes off in two weeks and on average is 75mm thick, the ufh has been pressure tested so i,ve told the customer that i,ll return on the 19th february and take it from there.

 

[nalla]

Nalla, the guidelines for screed and wet UFH are:
Lay screed and wait at least 3 weeks for movement and shrinkage.
Switch on UFH at a rate of 5degs every 24 hours upto max operating temp.
Maintain max temp for 3 days then turn off.
Wait 48 hours then tile.

However, if you are using a natural stone tile then use Ditra.
If using Porcelain then it should be fine to tile without Ditra.

Before you do the above, I suggest you find a plastic bucket or a sheet of plastic with a tile on top and place it on the floor for 24 hours. If after 24 hours there is moisture then it is not safe to do any of the above.

I went to a house just before Xmas and the owners said the screed was dry. I put a plastic paint tub on the floor and picked it up 15mins later. There was a wet patch on the screed in the shape of the bottom of the bucket!

The tiles are natural stone, after primming i was going to lay them directly on to the screed as they are with RSF (weber)

 

[Ttt1601]

I had a similqr problem to this not so long ago in regards to ufh not being commission ed as the tank and boiler were not going to be fitted until last to the air recirculation system and some other stuff, had a good chat with the main contractor, who is a good mate of mine and a plumber buy trade, we came up with the solution of using an electric water heater, all be it a fairly large one, with the ufh system full, he did what he had to to get the electric heater running the ufh, so manged to fully commissioned first

 

[Andy Allen]

The tiles are natural stone, after primming i was going to lay them directly on to the screed as they are with RSF (weber)

You Really need to use a decoupler with natural stone and ufh........

 

[Dumbo]

I had a similqr problem to this not so long ago in regards to ufh not being commission ed as the tank and boiler were not going to be fitted until last to the air recirculation system and some other stuff, had a good chat with the main contractor, who is a good mate of mine and a plumber buy trade, we came up with the solution of using an electric water heater, all be it a fairly large one, with the ufh system full, he did what he had to to get the electric heater running the ufh, so manged to fully commissioned first

Apparently there is a builder round our called Ray Ferguson who does this as a matter of course.

 

[Flintstone]

This job is not going to end well if you stick the stone to this screed after only 6 weeks with no ufh commissioning and no uncoupling.
I would insist on commissioning the ufh, then fit durabase mat or ditra to control the moisture which is left

 

[Time's Ran Out]

You came, you asked, we replied, we recommend.
Again little bits of info dragged out.
It will end in tears!

 

[Dumbo]

I've been in touch with the person who laid the screed and he told me that the screed he used goes off in two weeks and on average is 75mm thick, the ufh has been pressure tested so i,ve told the customer that i,ll return on the 19th february and take it from there.

And what does he call dry

 

[Just Rizzle]

you need to
a) take a moisture reading to ensure floor is dry.
b)lay a decoupling mat as sand and cement screed will expand and contract and the floor will crack so will the tiles if laid directly on to the screed
c)it would be prefered to commission the ufh but if you have it under preasure to at least 3bar and remaining on during the laying you should be ok