Advice on tiling onto "overlay" underfloor heating

[Jonner]

Hi, my name is Jon

I have already had a look around the forum and it has already been really useful regarding tiling onto an overlay underfloor heating system, but it has raised a few questions!

I will shortly be starting a floor tilling job onto an overlay (water based) underfloor heating system. The underfloor system is in conjunction with an Air Source Heat Pump (flow temperatures about 35deg C).

The PE-RT (polyethylene pipes are laid into a foil insulated polystyrene foam). From what I have read on the forum I am then planning to do the following:

• Bond on a “backer board” using a flexible adhesive – I was planning on using 12mm thick minimum. Is thicker board better? Should the backer board be screwed down?)
• Lay down a de-coupling membrane
• Bond either stone or ceramic tiles to the backer board

Please could you advise if the steps I am proposing are correct and any materials you would recommend.

Any help/advice really appreciated, thank you.

Best Wishes

Jon

 

[Old Mod]

There are other overlay systems that are much safer to use Jon, Polypipe being one, or other similar types. These are installed in to inert gypsum or cement based boards and are far more suited to your application.
You may also consider Bekotec therm from schluter, it’s a very low profile ufh system fitted in just 35mm of screed (I think it’s 35mm) which can be run hot or cold. I must admit I don’t know off top of my head if it’s suitable with your heat source. But knowing schluter, I’d be surprised if it wasn’t.

 

[Jonner]

Hi Marc
Many thanks for these comments.
We are actually now considering the attached as our favorite option, following further discussion with our heat pump installer.
Any experience or comments?
Cheers Jon

 

[Jonner]

It looks very similar to the Schluter system too )

 

[Old Mod]

The schluter system has a sand and cement screed applied to the top.
Are using the plastic or gypsum boards Jon?

 

[Flintstone]

Schluter system looks very impressive. You can use it on top of various sub floors and it’s only 25mm total build up

 

[Old Mod]

Schluter system looks very impressive. You can use it on top of various sub floors and it’s only 25mm total build up

Oh 25 is it Andy, thought it was 35.

I don’t think I’m grasping this system, does it use both the plastic and gypsum boards, or is it either or?

 

[Jonner]

From the download i send of the Low Pro 10 it looks like it uses gypsum (or similar) boards for the straight sections and includes the curve detail for one of the ends and then you use the plastic castilation panels to make the other curve end.

Not sure if we need to put additional insulation down on the floor first?

 

[Old Mod]

Oh ok, a little odd, but ok.
So first thing to note, gypsum boards.
Gypsum and cement don’t mix well. Make sure the gypsum boards are well primed, not with pva! But an acrylic or an sbr based primer. Minimum 2 coats.
Pressurise system as suggested and leave at around 5-6 bar if possible. Latex over pipes regardless of what instructions say. It will eliminate voids beneath your tiles and afford a better transfer of heat to your tiles. You can use an anti fracture mat as opposed to a full decoupler. Few differences but in essence an anti fracture mat is only 1mm thick as opposed to 4-5 with a decoupler. Let any decoupler or anti fracture mat cure overnight. Do not tile it straight away as suggested. Then tile.
Do not use suggested adhesive unless a professional tiler is doing the job. You WILL throw away more than you use if you are doing the Tiling. It’s one of the most difficult adhesives out there

 

[Jonner]

Thanks again Marc
on page 5 they mention "schnellgrund" primer to seal the gypsum
I will look onto acrylic or sbr primers as i will be doing this bit once pipe is laid

As i am doing the tiling was thinking of going for de-coupler (belt and braces). Did not realise that the decouple had to be "bonded". I guess with a felxible tile adhesive?
Please could you suggest an adhesive that i might have some success with, as yes i am planning on tiling
Cheers Jon

 

[Old Mod]

What is your tile choice Jon, I apologise if it’s been mentioned already.

 

[Uheat - Jake]

Very interesting thread...

The Hetta system is a popular one which many suppliers of UFH sell, however any type of EPS or XPS Polystyrene boards need a overboard before any form of tile can be applied to it. These systems are really suited for a Engineered Wood or Laminate. You can use a screed board over the top of it which is then fixed to the sub base however you have to be very careful of the pipes and where you're placing the screws.
These very reasons are why there's a new type of product on the market which is the Gypsum Retrofit panels which are a solid gypsum board which can accept a tile directly laid on top. The Gypsum boards have certainly become more popular recently due to not needing any extra materials. We supply a 18mm Version of this panel with pre-grooved pipe channels and end returns built in, suitable for a 12mm PERT Pipe. These boards can be primmed on the face and base before any adhesive or leveller is applied.
With our boards we state that the unused pipe channels need to be filled with compound before either a decoupling or tile is laid, this removes any voids that could be under the floor. I've attached a few photos from customers installations. If anyone needs any help on a system or installation, give me a call or send me a PM as we're happy to help everytime!

 

[Old Mod]

there's a new type of product on the market which is the Gypsum Retrofit panels which are a solid gypsum board which can accept a tile directly laid on top.

The polypipe system which has been around a while uses gypsum boards, and after a few years of publishing different installation techniques, they’ve finally produced a method statement in lines with what we want as fixers.
Which is to have a latex layer over the pipes of approx 5mm, then preference is a
decoupler/anti fracture mat, then tile.
The mat not being essential for porcelain but definitely with natural products and thin tile, but always preferred.
Although there are Tiler’s that will fix straight to the boards, there’s certainly another school of thought that feels that this is not the most effective method.
Also a lot of people miss the fact that they are gypsum and not cement!!
Therefore, priming correctly is essential, whether it be before latex or adhesive.
They are not a match made in heaven.

 

[Uheat - Jake]

The polypipe system which has been around a while uses gypsum boards, and after a few years of publishing different installation techniques, they’ve finally produced a method statement in lines with what we want as fixers.
Which is to have a latex layer over the pipes of approx 5mm, then preference is a
decoupler/anti fracture mat, then tile.
The mat not being essential for porcelain but definitely with natural products and thin tile, but always preferred.
Although there are Tiler’s that will fix straight to the boards, there’s certainly another school of thought that feels that this is not the most effective method.
Also a lot of people miss the fact that they are gypsum and not cement!!
Therefore, priming correctly is essential, whether it be before latex or adhesive.
They are not a match made in heaven.

A Flexible SLC is perfectly fine to go over our panels as well before a decoupler is applied and is also the easier method as it'll fill the unused pipe channels as well.

 

[One Day]

....
Also a lot of people miss the fact that they are gypsum and not cement!!
Therefore, priming correctly is essential, whether it be before latex or adhesive.

THIS!!! (x100)

 

[Jonner]

Thanks again everyone. Your comments are making me feel more and more confident about the gypsum board based UFH that we are now looking at from Nu Heat called Lo Pro 10.
I will ensure that the gypsum boards are sealed/primed with SBR prior to install followed by de-coupler.

Marc - as yet no decisions re the tiles! Although it is an old cottage we are currently not thinking natural stone due to the need for sealing and maintenance. We are after something hard wearing, with a natural stone type texture/pattern (not polished smooth) in light tan/beige colour, oh and not expensive as we have about 60m2 to tile. So any recommendations on tiles and then adhesive would be great.

 

[Jonner]

Hi All
As mentioned previously thank so much for all the help provided here. We are going ahead with the Nu Heat low pro 10 approach. Once down we are going to be laying Limestone tiles of 22mm thickness.
Any further comments/advise is most welcome.
Best Wishes
Jon

 

[Qwerty]

My only (and fairly significant) comment is that the Nuheat low pro 10 system appears to be only suitable for dry lay flooring, not tiles.

 

[Flintstone]

With regards to your tile, I have a job in the pipeline with some 600x400 matt porcelain, which are a stone look tile and they are very realistic. I will try and get some photos if you like this week.

 

[Jonner]

Thank ACT that would be great.

 

[Jonner]

Hi Plan Tec
having looked at all of the Low Pro 10 data sheets and posted them on here last week i am surprised that you dont think it suitable for tiling. It says on the data sheet that tiles are fine, and having spoken to them direct they said tiling was "the best option". If you have had another experience then please let me know. Many thanks Jon

 

[Qwerty]

Hi @Jonner . I said it 'appears' to be only suitable for dry lay flooring based on this....

If you have the confidence and assurance by the company to tile to it, then that is good news. I haven't had the benefit of speaking to the company which you obviously have. Have you physically seen the product tiled?

 

[Jonner]

Hi Plan Tec
Many thanks for the comments. You are right i have not actually seen tiles down in place i am going in word of mouth and previous installers comments. Which i guess is a risk.
Having spoken to Nu Heat and also a lot of feedback from the guys on here the gypsum based board system seems good for tiling.
Many thanks Jon

 

[Flintstone]

Hi @Jonner

Here’s the photo I promised of the stone effect porcelain, 600x400 rectified edge, matt finish.