Hello experienced craftsmen, I need a little advice. I am in the process of building a bathroom which is constructed so far as follows. The floor is normal chipboard floor which has been overlaid with 18mm wbp ply screwed at 300mm or less centers, all walls within the shower area are Wedi on stud wall or lightweight block the shower base is a Wedi Fundo and all other walls are covered with Marmox 12.5 mm, all joints are sealed with Wedi tape, Bal single part flexi adhesive was used under and over the tape. As yet I have not treated the floor but planned to use Durabase uncoupling membrane stuck down with Bal single part flexible and water-resistant adhesive, then electrical UFH, then self levelling flexible screed then more Bal then 300x400 travatine tiles, two other walls have porcelain the shower tray will have travatine mosaics and the biggest wall with a big mirror on will be oyster coloured slate. The shower area will be almost enclosed on three sides with walls the last opening will have a 800mm glass screen leaving 500mm of opening to walk in and out of.

My question is do I put the UFH down first then self levelling screed then decoupling membrane or is it Durabase then UFH then screed, the adhesive instructions say sealing is in with the mix (I think) but dont expect the area outside of the shower to get that wet, so a further question at the back of my mind is should I also seal the WBP ply?

Ufh, then slc, then decoupling membrane

Thanks for the speedy response whitebeam

No problem, just remember to use some thin tape to hold the wires down before you self level otherwise the slc could push the wires up and make you use more tile addy than is needed.

Another thread on this forum suggested hot-melt glue dotted at intervals around the perimeter of the ufl, was planning to do that, seemed like a good tip, thanks though for thinking for me, this is the first and I suspect last bathroom.

Thats good as well

As you are using a text book overboard method you can use Dura-wp to uncouple and tank your floor (providing floor not over 8m2). The Dura-wp is a lot thinner than Dura-ci and so much easier to handle in your situation.

Your lay order would then be

Floor
adhesive
Dura-wp (sticking is easier now)
slc
adhesive
tiles

Trying to make it easier

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Originally Posted by wetdec

As you are using a text book overboard method you can use Dura-wp to uncouple and tank your floor (providing floor not over 8m2). The Dura-wp is a lot thinner than Dura-ci and so much easier to handle in your situation.

Your lay order would then be

Floor
adhesive
Dura-wp (sticking is easier now)
slc
adhesive
tiles

Trying to make it easier

.

where would you sandwich the UFH Tony?

Ah 00ps sorry missed it, on top of the membrane b4 slc the tape will stick real good to the membrane as well


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I would agree with all above, I don't want to confuse the issue but Dural CI can go under ufh or over, without effecting thermal transfare

Keep up we talking bout wp not ci

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I am keeping up we are talking de-coupling membrane in 1st post (CI) WP is a tanking memrane nothing to do with de-coupling

As you are using a text book overboard method you can use Dura-wp to uncouple and tank your floor (providing floor not over 8m2). The Dura-wp is a lot thinner than Dura-ci and so much easier to handle in your situation.

As wp is a poly elastic core with fleeced surface it can be used in low traffic areas such as bathrooms, showers, wetrooms up to a size of say 8m2 providing the floor is 22-28mm plywood screwed to joist at 150-300 centres as per good practice.

In the event of latteral movement in the wood floor the fleece allows a release not unsimilar to the lower membrane of a specified uncoupling membrane as used on large high trafic floors such as kitchens halls conservatories etc where latteral movement is increased..

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The Durabase I have is an uncoupling membrane a bit like a sandwich of thin plastic with raised discs on one side, bought it of someone on the forum, may even have been you Wetdecs. All I need to know really is do I fit the ufh first then slc then durabase then tiles or is it durabase ufh slc then tiles, I have two conflicting sets of advice and to be honest it makes sense to me either way. Thanks to all contributors so far.

wetdecs i see that you advise using durabase wp membrane on the wetroom floor if under 8 sqm if plywood is 22-28mm thick. the OP's plywood floor is 18mm and mine is 12mm, is durabase wp still chosen therefore over the ci matting?

imo over that way you know you have an absolute bond between floor and membrane. As has been said either is ok................

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[QUOTE=Stevoe;356176]The Durabase I have is an uncoupling membrane a bit like a sandwich of thin plastic with raised discs on one side, bought it of someone on the forum, may even have been you Wetdecs. All I need to know really is do I fit the ufh first then slc then durabase then tiles or is it durabase ufh slc then tiles, I have two conflicting sets of advice and to be honest it makes sense to me either way. Thanks to all contributors so far.



Either way Stevoe mate, Gerard from Dural will confirm this.If you need his mob no. PM me or post again here. Ci is de-coupling WP primarily tanking

ufh
slc
ci
tiles

Durabase Ci Suppliment.


CI Matting – Underfloor Heating Systems



The increased stress within the installation caused by thermal movement can cause problems to the installer. Separation or Isolation Membranes are ideal for removing shear stress from tiled installations. This removes a major obstacle to fixer confidence in installing these systems.

By absorbing this stress the membrane allows the tiled surface to remain intact. The air spaces under the membrane have two benefits, they allow residual moisture to gradually escape therefore helping to prevent cracks forming in the substrate. The air spaces also allow the heat to be spread evenly across the floor surface making the heating action more general and effective.

CI matting requires no special precautions when used within a heated installation.

The only requirement is the selection of an adhesive suitable for use with the substrate. This adhesive must be capable of bonding to the substrate and achieving a mechanical fix with the fleece on the underside of CI matting.

The electrical heating elements should be installed onto the surface of the CI matting following the manufacturer’ instructions. Standard thin set adhesive can be used to fix tiles in place. A modified flexible grout should be used to complete the installation.


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Originally Posted by wetdec

Durabase Ci Suppliment.


CI Matting – Underfloor Heating Systems



The increased stress within the installation caused by thermal movement can cause problems to the installer. Separation or Isolation Membranes are ideal for removing shear stress from tiled installations. This removes a major obstacle to fixer confidence in installing these systems.

By absorbing this stress the membrane allows the tiled surface to remain intact. The air spaces under the membrane have two benefits, they allow residual moisture to gradually escape therefore helping to prevent cracks forming in the substrate. The air spaces also allow the heat to be spread evenly across the floor surface making the heating action more general and effective.

CI matting requires no special precautions when used within a heated installation.

The only requirement is the selection of an adhesive suitable for use with the substrate. This adhesive must be capable of bonding to the substrate and achieving a mechanical fix with the fleece on the underside of CI matting.

The electrical heating elements should be installed onto the surface of the CI matting following the manufacturer’ instructions. Standard thin set adhesive can be used to fix tiles in place. A modified flexible grout should be used to complete the installation.


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so do you stick the heating mat direct to the top of the ci and then flood with slc so as it fills the cavitys in the ci and then goes over the top of the matt? if you wern't using slc and decided to just tile direct onto the heating mat then wouldn't it be very difficult to force the adhesive threw the heating mat and being able to fill the cavitys in the ci? ensuring the cavitys are full? or would you suggest filling the cavitys in the ci first with tile adhesive allow to dry then heating matt then slc or just tile? I have done it the other way matt slc decoupler then tile and never had any issues. I have always thought that by doing it this way that any expansion caused by the heating matt will not affect the tiles due to the decoupler being between them. But it seems i could be wroung..

Originally Posted by peckers

so do you stick the heating mat direct to the top of the ci and then flood with slc so as it fills the cavitys in the ci and then goes over the top of the matt? if you wern't using slc and decided to just tile direct onto the heating mat then wouldn't it be very difficult to force the adhesive threw the heating mat and being able to fill the cavitys in the ci? ensuring the cavitys are full? or would you suggest filling the cavitys in the ci first with tile adhesive allow to dry then heating matt then slc or just tile? I have done it the other way matt slc decoupler then tile and never had any issues. I have always thought that by doing it this way that any expansion caused by the heating matt will not affect the tiles due to the decoupler being between them. But it seems i could be wroung..

We use a pourable adhesive over the cable (just cable not meshed) and bring it flush ready to tile. To fill the voids and leave to dry I supose is a possibility but would draw out your working time.

The heat from an underfloor cable doesnt have the capacity to crack the tiles. An uncoupling membrane used over a heated floor isolates the tiles from the screed movement during expansion and contraction which involves huge tensions and will crack your tiles.

The ci pdf doesnt cover this aspect so what I posted was written as a suppliment to the pdf.

The most importand bond when using an uncoupling membrane is the one to the actual floor the less fiddling in that area the better.

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Your welcome.........

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IMO an Uncoupling membrane works more efficiently over the top and just the tiles on it..

They can be used either way but on top makes the uncoupling work better, as in uncoupled from ALL stress.

Ditra do point this issue out, so i wonder why Dural don't..??

Cant answer that one Dave you better ask them probably involves maths. Would say tho if your cable is under the membrane and the screed tears so does your cable as there is no give there............

By uncoupling you are isolating a problem should it occur the problem originating in this instance at the screed they are designed primarily to counter screed difficulties

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just thinking if it was a wetroom wouldnt it be better to lay wp over the whole floor and tray and not underneath?

ted

Ye dead right Neil

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