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Green Building Bible, Fourth Edition
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  1.  
    Hi all, I am in the process of installing wet underfloor heating in pre-grooved flooring board overlaid with plywood on my first floor. I want to turn one end of my bathroom into a wet room where I will place the bath and shower. There are many tanking products, boards etc. out there but I can't find any specific solutions. The builder is saying not to put UFH under the tanked end part as he can't 'tank wood'. Most of the overlay boards which can be tanked are insulating.

    Any similar experiences? Is a cement based board a possibility?
    • CommentAuthorphiledge
    • CommentTimeApr 26th 2021
     
    If your builder is saying he cant tank wood, you may need to get someone else in to do the tanking!!! We used Impey Waterguard over Jackoboard insulated backer board but Waterguard can be used directly on structurally sound wood- ply in your case. Surface needs to be smooth and primed

    If youve not decided on a tanking system, have you sorted out a former for the shower floor and installed a drain as they all need to be coordinated for compatibilty.
  2.  
    Thanks I will take a look at Waterguard. Just looking at shower formers which can be placed on the joists to create a fall (with a bit of structural work to create a platform). Its amazing the details you miss on a big project!
    • CommentAuthorphiledge
    • CommentTimeApr 26th 2021
     
    Getting a wet room right is a big project on its own!!
    •  
      CommentAuthordjh
    • CommentTimeApr 26th 2021
     
    We didn't want tiles, so we just put commercial vinyl (hospital style) glued directly over the chipboard floor. We used a plastic former around the drain but note that since the falls don't extend to the whole floor beyond the former, you still get some water that needs sweeping towards the drain.
  3.  
    Posted By: modernvictorianHi all, I am in the process of installing wet underfloor heating in pre-grooved flooring board overlaid with plywood on my first floor. I want to turn one end of my bathroom into a wet room where I will place the bath and shower. There are many tanking products, boards etc. out there but I can't find any specific solutions. The builder is saying not to put UFH under the tanked end part as he can't 'tank wood'. Most of the overlay boards which can be tanked are insulating.

    Any similar experiences? Is a cement based board a possibility?


    Can't you ask him what he would normally have as a base material? Most houses have chipboard wooden floors so what you're doing is hardly unusual. You don't normally put UFH under a shower - we didn't under our resin tray - but I cant remember the reasoning - perhaps that you don't want to heat the trap and cause it to dry out (but that wouldn't be relevant to most of the area of it.
    • CommentAuthorphiledge
    • CommentTimeApr 26th 2021 edited
     
    Posted By: Simon Still You don't normally put UFH under a shower - we didn't under our resin tray


    Maybe not under a shower tray, but definitely under a wet room shower floor.

    I think with wet UFH you can probably run the pipes under everything but with electric UFH, the cables can overheat if theres "insulators" over the top that stop the heat dissipating.
  4.  
    I think I can now solve the issue of 'tanking wood' by using a membrane as described above.

    It would be great to have the UFH pipes on the shower floor but all of the tray formers I have found are made of an insulating material.

    The layout will be something like this - bath and shower at the end of the room with a drain running across the width. The best way to do this I think would be to install sloping board across the entire width of the shower/bath area to avoid any spots where the water could pool. But it is a shame I can't find any sloping boards which will let heat through.
      Capture - bathroom.JPG
    • CommentAuthorphiledge
    • CommentTimeApr 26th 2021
     
    What floor finish are you using? If its an Altro type vinyl you should be able to use your pre grooved board with ply covering as in the rest of the first floor. If its tiled you could put a couple of square metres of electric mat under the tiles in the shower area. A vinyl covering on wood is likley to feel reasonably warm underfoot but if its tiled, UFH is a must:)
    •  
      CommentAuthordjh
    • CommentTimeApr 26th 2021
     
    Posted By: modernvictorianIt would be great to have the UFH pipes on the shower floor but all of the tray formers I have found are made of an insulating material.

    I think we used an Impey Aqua-Grade former, which is an open plastic structure.

    Another approach might be to make some firring strips and use those to make the floor slope down to a linear drain. Matching heights everywhere will need some thought.

    You'll need to think about the load imposed by a bath on top of whatever structure you put in place. A bath full of water weighs noticeably more than a person.

    Posted By: philedgeIf its an Altro type vinyl

    Yes, I believe that's what we've got.
    • CommentAuthorMike1
    • CommentTimeApr 27th 2021
     
    Posted By: Simon StillYou don't normally put UFH under a shower - we didn't under our resin tray - but I cant remember the reasoning - perhaps that you don't want to heat the trap and cause it to dry out
    That's certainly the reasoning I've seen before. However it's pretty unlikely to dry out unless you leave the house heated for quite a few days, as there's the option of using a waterless trap if you're worried.

    Even if you omit the UFCH beneath the tray, the floor temperature won't be too many degrees colder, so it's probably not going to make a big difference.
    •  
      CommentAuthordjh
    • CommentTimeApr 27th 2021
     
    Posted By: Mike1However it's pretty unlikely to dry out unless you leave the house heated for quite a few days, as there's the option of using a waterless trap if you're worried.

    FWIW, in our house with MVHR we go around and fill bath and shower traps once a month unless they've been used. That seems to be frequent enough to prevent drying out, but we've had them dry out if we leave it much longer. We have a waterless trap on the condensation drain from the MVHR itself, since we anticipated the problem there :bigsmile:
    • CommentAuthorMike1
    • CommentTimeApr 27th 2021 edited
     
    I should have added that in the past I've run UFCH pipes everywhere in all rooms, only leaving gaps if I'm planning to drill the floor, and I'll be doing the same again in my next projects.
    • CommentAuthorJonti
    • CommentTimeApr 27th 2021
     
    What has UFH to do with tanking or not? I think it is a case of your builder not being familiar with working with UFH. In addition, if you do a full tanking of the room then you won't need a shower tray. It is not so usual in the UK but is commonplace across many parts of Europe so maybe that might be the pace to look for answers.
    • CommentAuthorphiledge
    • CommentTimeApr 27th 2021
     
    Posted By: JontiWhat has UFH to do with tanking or not?

    It was the OPs original question!
  5.  
    Yes. Creating a slope is the problem. I think as someone said earlier the most practical solution might be to not include UFH at the end of the room in the shower area. Quite keen to go for vinyl floor and given its a first floor I don't think the floor will be too cold at that end.
    • CommentAuthorphiledge
    • CommentTimeApr 28th 2021
     
    I dont think vinyl over timber wood feel too cold but I cant see why a decent joiner wouldnt be able to pack up the same grooved flooring used for the rest of the first floor to give a fall to a linear drain.

    If you are tanking the room with vinyl, make sure you get all the joints professionally welded by someone experienced and with the correct tools.
    • CommentAuthorJonti
    • CommentTimeApr 28th 2021
     
    Posted By: modernvictorianYes. Creating a slope is the problem. I think as someone said earlier the most practical solution might be to not include UFH at the end of the room in the shower area. Quite keen to go for vinyl floor and given its a first floor I don't think the floor will be too cold at that end.


    Why is it hard to create a slope? I don't see what difference it makes if you have UFH under a tanked floor or not and neither why it should be any harder to create a sloping floor rather than a flat one. I have seen both hundreds of times!!!!
  6.  
    OK does anyone have a trusted method to create the slope with the grooved UFH boards without using the former boards?
    • CommentAuthorphiledge
    • CommentTimeApr 28th 2021
     
    In the first post you say you are using pre grooved floor boards with a ply overlay. Assuming these are sitting on joists then either the grooved flooring or ply or the combination of both form the structural floor boarding. Where you want a slope you add packers to the joists to give increasing height as the floor moves away from the linear drain. If the joists run parallel to the drain then the packers will be long thin parallel strips of wood/plastic increasing in thickness by a few mm for each joist as you move away from the drain. If the joists run at 90 degrees to the drain then the packers will be long thin wedges.

    A joiner will be able to sort out all the packers if you tell him the slope you want.
  7.  
    Brilliant thanks. I can probably work out the correct angle based on the boards you can buy. I'm hoping that the job will be made easier by having the whole width of the room on the same slope.
  8.  
    Just a warning - personally, I think wet rooms are a really bad idea in nearly all cases. Fine in hot dry countries where it's warm. Maybe ok in a modern well insulated and airtight house with MVHR.

    But the reality doesn't often match the idea - what it really means is you have a wet and slippery bathroom floor fo the next person to use. maybe fine in an ensuite but not great in a family bathroom.

    Add to that tanking really needs to be top notch and with a floor with zero movement (unlikely on the upper floors of a victorian house). We built a shower cubicle using an impey 'wet room' base in our last house and despite a really good structure it still moved enough that the tile grout was a regular problem. If you are going to do a wet room, I'd definitely advice a one piece shower tray rather than tiled floor (with level tiles around it)
    • CommentAuthorphiledge
    • CommentTimeApr 28th 2021
     
    Weve got both a tiled wet room over an insulated timber floor and an Altro covered screeded floor. No problems with slipping on either but you need to choose tiles intended for wet areas. Altro is designed for wet rooms and is non slip.

    Personally I think if the tanking/Altro is installed properly then your unlikely to have any more problems with a wet room over a conventional shower tray, but proper install is the key:)
    •  
      CommentAuthordjh
    • CommentTimeApr 28th 2021
     
    In our house we have no problems with our wet room. We do have MVHR, we don't have UFH. We have an Altro floor, wrapped up the walls at the edges, professionally installed so it's all welded/glued or whatever they do. Never a hint of slipping, even when wet; the floor dries naturally in a reasonable time. There was a more slippery surface in the shower tray in another room initially, but thankfully that has got better over time (presumably some sort of fine surface finish). In our case it is our downstairs 'lifetime' shower, mostly used as a guest room at present. We did fit a screen to separate the WC from the shower area - the idea of a wet seat or wet toilet paper doesn't really float my boat.

    I don't see any problem with a wet room in this country, as long as it is done right. I wouldn't recommend a tiled surface
  9.  
    Posted By: Simon StillJust a warning - personally, I think wet rooms are a really bad idea in nearly all cases. Fine in hot dry countries where it's warm. Maybe ok in a modern well insulated and airtight house with MVHR.


    I do hear you. I've known a few cold, wet, mouldy wet rooms. But I will have MVHR and despite being an older property I have insulated throughout. Hoping the 'only water at one end' design will also help.
    • CommentAuthorJonti
    • CommentTimeApr 28th 2021
     
    I have lived in several properties with wet rooms and have never had problems with slippery floors or damp, mould, etc. Such problems are to do with poor choices of materials and bad ventilation not the wet room concept. If you tank the whole room which can't be a bad thing this does not mean you cannot restrict the water to certain parts. Ergo, you don't have to spray water over the entire room because of the name it just means it is less of a problem if occasionally some members of the family do.
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