Hardiebacker under Insulation boards?

[Bathfix Bob]

Hi Guys, in my current bathroom job its been a late decision to have an electric underfloor heating mat.

Its 18mm chipboard well screwed down and I've bought, cut and laid 6mm Hardiebacker but not fixed or glued it yet.

Shall i do away with the Hardie and just screw and glue 6mm insulation boards down or shall I glue and screw hardie as normal and then insulation board on top? I want to keep the hardie really but I suppose I can use it on my next job.

Tiles will be porcelain.

 

[hmtiling]

Get rid of the Hardie if the floor is sound.

 

[Stef]

It will be fine to fit ufh on top of Hardie, not ideal as you would be better with thermal.
Might not perform as efficiently but it will be pennies of an extra cost.

 

[Flintstone]

Personally I would go over the hardie with the ufh

 

[hmtiling]

I was under the impression Hardie was a terrible insulator hence it being specified for overboarding wet ufh sometimes

 

[Bathfix Bob]

Thanks guys,

It's seems some people love insulation boards and some hate them, my local independent tile shop dosnt sell them and whenever I ask they say theres no call for them as everyone tiles on Hardie.
I have to go to the tile Giant in the next town if I need them.
Can someone explain why it's okay to tile on something so soft like foam cored boards when we do everything we can to make floors rigid?
The smaller the tiles the more likely they would 'sink' into the board.

 

[Ttt1601]

You've kind of answer your own question there, it's about point loading those thermal boards are are bloody solid if you've got a large surface area on them, but hit them with a hammer you'll go through it

 

[Dumbo]

If I'm correct most insulation board manufacturers are happy with a tile size down to 50mmx50mm although one of the ones that marmox make are happy to go slightly smaller I believe but you would have to check with them .

 

[hmtiling]

If I'm correct most insulation board manufacturers are happy with a tile size down to 50mmx50mm although one of the ones that marmox make are happy to go slightly smaller I believe but you would have to check with them .

Agree, although that may not be the case once latexed

 

[Dumbo]

Agree, although that may not be the case once latexed

Please educate as to why

 

[hmtiling]

The latex would spread the load and therefore cancel the point loading issues

 

[Dumbo]

I was thinking you were talking of a decrease in point loading Tile size . Ie increase issues

 

[hmtiling]

I was thinking you were talking of a decrease in point loading Tile size . Ie increase issues

I mean you can use smaller tiles once latexed.

 

[Dumbo]

Yes I got it . My reply confusingly worded

 

[hmtiling]

Yes I got it . My reply confusingly worded

We got there

 

[Bathfix Bob]

Right this is good, I'm going to glue and screw down my Hardie, then UFH, SLC and tile.
Thanks guts. ..

 

[Dan]

Thanks guys,

It's seems some people love insulation boards and some hate them, my local independent tile shop dosnt sell them and whenever I ask they say theres no call for them as everyone tiles on Hardie.
I have to go to the tile Giant in the next town if I need them.
Can someone explain why it's okay to tile on something so soft like foam cored boards when we do everything we can to make floors rigid?
The smaller the tiles the more likely they would 'sink' into the board.

Order online. www.uheat.co.uk

 

[Steve_Bcs]

Glad I found this post ! just had a quote from Andrew at UHeat which includes insulation boards for under the mats. Its for an en-suite 2.0m x 1.6m incorporating a 1000 x 800 offset quad shower with 45mm tray, sink vanity and toilet. I was planning to use 6mm hardiebacker over the existing T&G but then the prospect of introducing 6mm insulation as well confused me. However from reading the above am I right in my understanding that its one or the other, then SLC then tile on top ( Porcelain) . Is there a particular type of SLC or will any suffice.? tia

 

[Old Mod]

Have you used slc before?

 

[Steve_Bcs]

not used self leveling compound before & first time using under floor heating. just want to make sure I get it right hence asking on here.

 

[Old Mod]

Yeah all fair enough.
One thing to know about SLC it’s NOT self levelling.
Not completely anyway, it does need some help.
Buy a reputable brand, ie Isomat, Mapei, Tilemaster.
Follow instructions carefully.
It’s not a cheap product, so don’t buy Cheap.
Put a few markers down that show you the low points and work to a level set by your markers.
You can use screws in to floor or silicone joiners packers down to mark your levels.
That’s a very basic outline of how to get a reasonable result.

 

[Steve_Bcs]

thanks 3_fall.

 

[Dumbo]

To get a good finish a spiked roller is really usefull

 

[Steve_Bcs]

spiked roller to remove air I presume? would that still be ok to use over an electric under floor heating mat though?

 

[Dumbo]

I use a plastic spiked roller over underfloor heating and have never had a problem . Not only does it remove air it helps the slc run so helps remove trowel lines and also where you pour slc next to slc you've just laid . Don't get one with 10mm spikes they are not worth bothering with . As much as it pains me to say topps tiles don't do a bad one .

 

[Steve_Bcs]

Thanks. I think I am on the right track now

 

[Steve_Bcs]

Just completed my first ever ufh install & slc placement. I got the spiked roller from Topps too. I did forget to secure the joiners’ packers as my levelling guide - discovered they float! Anyway the floor was fairly level to start with and the Slc just covers the ufh wiring.

I’ll check the level again in the morning. If, it turns out its not quite level what would be the best remedy? Also, do I need to apply any primer before tiling onto slc?

 

[Qwerty]

Just use a small amount of slc to make good. Scraping or sanding high spots can be risky!

Yes, prime the slc before tiling.

 

[GoneGuy]

As @Plan Tec Tiling said, and prime with a sbr

 

[Steve_Bcs]

Thanks guys.
SBR? Is that a particular brand of primer? Can i use the same before tiling?