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Jack Yerou

Hi there, I am not a tiler. I am a carrying out my first self build and would be grateful for some assistance:

I have 2 questions:

(1)My builder wants to use 6mm hardiback board on the floors in the bathrooms. This will be laid over 18mm ply. The bathrooms are to have electric under floor heating. It has been suggested to me that hardibacker may not have the necessary insulation qualities that would be adequate for underfloor heating. I could not find anything on the web about hardibacker board but did find information on Marmox which is apparently suitable as a backing board for tiling and also as insulation for under floor electric heating. My builder is saying that hardibacker is adequite because we are insulating with rockwall between the 200mm wooden joist. Does anyone have a view on this?
(2)The ground floor is to have piped under floor heating. I have had contradictory advise from two experienced tilers regarding whether a decoupling mat is necessary. The whole ground floor an area of 187 square metres will be screeded by a professional screeding company so presumably expansion joints will be allowed for. One tiler is adament that no decoupling matt should be necessary providing an appropriate flexible adhesive is used the other is insistant that a decoupling mat is necessary to prevent cracking. My understanding is that a decoupling mat will cost about £6 per square metre to buy approx. £3 per metre to lay so this is a significant additional cost. If I I was to use a decoupling mat which type is recommended and where is the best place to buy it.

I would welcome any comments.

Jack
 
for that kind of area i would suggest a decoupling mat,there will also have to be some kind of axpansion joints put in at seperate intervals(your doorways should suffice for this)

:welcome:to the forum
 
Hello and welcome..

The ply is sort of an insulator as it is... so not really needed for timber floors like that but it will reduce running costs to use a board like marmox.


As for the large floor area, then this is dependent on what tiles you are installing as well..

Un-coupling membrane are great for new screeds that are prone to stress fractures and also with it being piped heating it does cut down excess stress caused to the tiled installation.

It is not a necessity to have it installed but it is a fail safe method , so both tilers are correct.

Say you were having stone tiles like travertine fixed then i would also recommend the membrane , as this will benefit from being un-coupled as stress will affect it more than say a porcelain tile.

If the screed is new and not yet fully dry then the membrane can be used to speed up the tiling process as it allows the screed to breath and any moisture vapour will disperse on the underside of the un-coupling membrane.

2 i recommend are Schluters Ditra mat and Durals Ci mat..as this are both vapour equalisation membranes and un-couplers.

The choice is yours but the fail safe option is Always use an un-coupler..:thumbsup:
 

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