Full floor prep

[kaharrison9]

Evening all
Wondering for your thoughts on the best way to prep a 50sm2 that i may have coming up.
It's an exstension and the floor will be running through the new and old part of the house.The old floor is to be taken up back to the joists
There is going to be a wet ufh system and the buider has suggested chipboarding(18mm) the whole area,laying the ufh on top then 6mm ply screwed over,then tiled.
I suggest hardiebacker 12mm on the joists,then ufh,uncoupling membrane then tile would that be fine or have i missed something obvious?
Possible questions could the 18mm ply replace the cement board?
If fine could ditra go straight over the ufh heating channels filled with adhesive or would a slc be best
Cheers for your thoughts
Kev

 

[White Room]

How thick are the wet ufh pipes

 

[kaharrison9]

the grid system that the pipes fix into 18mm thick is all i know at the moment.

 

[Gazzer]

Evening all
Wondering for your thoughts on the best way to prep a 50sm2 that i may have coming up.
It's an exstension and the floor will be running through the new and old part of the house.The old floor is to be taken up back to the joists
There is going to be a wet ufh system and the buider has suggested chipboarding(18mm) the whole area,laying the ufh on top then 6mm ply screwed over,then tiled.
I suggest hardiebacker 12mm on the joists,then ufh,uncoupling membrane then tile would that be fine or have i missed something obvious?
Possible questions could the 18mm ply replace the cement board?
If fine could ditra go straight over the ufh heating channels filled with adhesive or would a slc be best
Cheers for your thoughts
Kev

Is this an error ? Are you specifying 12mm Hardibacker straight onto the joists ?????

 

[kaharrison9]

Not an error,it's what i'm asking before i contact the customer.
Can 12mm cement board go straight onto joists as i would have thought it was more than equal in strength to a similar thickness ply and a more stable background with the heating if possible.
If i'm way off the mark here could you please tell me how you would spec the prepping
Cheers

 

[Gazzer]

The cement board will not have the strength you require. You will have to use Ply or even chipboard for the strength, preferably the former (Ply)
Now after the UFH system has been installed what do you propose ? Which system is it ? Does it have its own backer boards with grooves for pipes or free lay ?

 

[kaharrison9]

That's good to find out the cement board hasn't the strength.
Would 18mm ply be enough or needs to be thicker?
As i mentioned to Whitebeam at the moment dont have to much info on the system(talked over the phone) though it does have 18mm boards with grooves for the pipes.
I was thinking of going straight over with an uncoupling membrane,would you?

 

[Gazzer]

The only way you will know if the floor is strong enough is to try it. If the joists are visiable then why not add extra noggins or even laminate teh sides of the joists with 18mm ply to add strength.

Without knowing the actual scale of the floor its hard to tell. 50m2 could be 25m long and 2m wide ?
If its the polypipe type system the boards need too be fixed to the substrate and then I have in the past used SLC over then Dural Ci then tile.

 

[kaharrison9]

I am see the customer soon so will have a clearer picture.
Can i ask why do you self level. Is this to bridge over the pipes or for a better surface to tile on?
Could the Dural not go direct onto the substrate using a quality adhesive like Keraquick and at the same time filling the channels with adhesive
Thanks again

 

[Rob Z]

Hi Kev

It's good to remember "the 4 S's" when deciding what to do on the floor (for you former military men this is not the same as the 3 S's:smilewinkgrin: ).

The four S's:

Size: of the joists
Span: unsupported span of the joists
Spacing: the on-center spacing of the joists
Species: the type of wood


If you are able to determine the above information, it goes a long way towards helping to decide what the best approach is to prep the substrate. There are various "deflectometers" on the web that help to calculate if a floor is suitable for tile or not. I can point you in the right direction if you're interested.

 

[kaharrison9]

Hi Rob
That would be certainly an interest.
Not heard of 'deflectometers' before,anything that helps back up a judgement is worth knowing about.
Thanks
Kev

 

[Gazzer]

Preparation is King...!
I used SLC because the surface that the polypie system gave was not flat due to the roundness of the pipes. Either way the floor has to be flat and the best way is to use SLC.

 

[kaharrison9]

Fully agree about preparation
One question had the polypipe system been flat and the pipes sunken into the grooves would you have been happy to put dural directly onto the heating boards and fill the void around the pipe and channel with an S1 adhesive.
Thanks for your time SR

 

[Gazzer]

Not really, no. I feel SLC gives the best surface for Ditra etc. Had you said you wanted to tile direct to polypipe then I may have gone just with adhesive.

 

[kaharrison9]

Actually seeing the customer later this week and the method i propose on top of the bare joists.
Extra noggins where seems needed
18mm wpb ply screwed down on top
The wet system panels then placed down and also screwed down onto the ply and joists
A latex based slc poured over the panels(2-3mm depth) and the pipe channels
Then finally dural ci matting.
Would that sequence appear to give us the best chance for a long tem instalation.
Cheers again

 

[Gazzer]

Actually seeing the customer later this week and the method i propose on top of the bare joists.
Extra noggins where seems needed
18mm wpb ply screwed down on top
The wet system panels then placed down and also screwed down onto the ply and joists
A latex based slc poured over the panels(2-3mm depth) and the pipe channels
Then finally dural ci matting.
Would that sequence appear to give us the best chance for a long tem instalation.
Cheers again

I would go with Mapei Renovation screed, cheaper than latex based . Good stuff too

 

[kaharrison9]

Will check that out,thanks again.
Was looking at polypipes advise when tiling on top and they just reccommend either tile directly on top with a flexible adhesive or put a 6mm ply down first!
Chatting to a pal who 2 years ago had a polypipe system on a floating floor and he said hardiebacker was screwed on top of the heating panel then tiled and never has had any problems.

 

[Gazzer]

Will check that out,thanks again.
Was looking at polypipes advise when tiling on top and they just reccommend either tile directly on top with a flexible adhesive or put a 6mm ply down first!
Chatting to a pal who 2 years ago had a polypipe system on a floating floor and he said hardiebacker was screwed on top of the heating panel then tiled and never has had any problems.

As long as the pipe system was covered with either SLC or backer board I would be happy. I would have thought SLC and Ditra /Dural Ci would be cheaper and safer than screwwing boards though and a few mm saving too.