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Housing - Renovation: How best to level out a wall

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    I have a bathroom wall (limestone / rubble) that has a 100 mm difference top to bottom. The top leans out from the bottom by 100 mm. The wall is about 70 cm thick, 2.7M high, quite stable and an outside wall, I think it was just built that way.

    The wall needs to be vertical, the question is how best to achieve this. There is not enough space to build a false wall in front of it. I am reluctant to batten out and plasterboard the wall as I am afraid that the battens will rot out in a few years and any damp from the wall would be v. detrimental to the plasterboard. Whilst the bottom part could be levelled with increasing thickness of render by the time you are half way up you are looking at about 60 mm of render which is about as much as I would want to put on, I can't help thinking that 100 mm of render at the top would be too much even if built up in layers.

    What would be the best way of levelling out this wall?
  2.  
    How about (multiple?) tile-backer boards bedded in plaster at the top running down to plaster only at the bottom?
  3.  
    I would be worried that the weight would pull the whole lot off the wall given that the greatest weight is at the top. (BTW the finish has to be tiled)
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      CommentAuthordjh
    • CommentTimeSep 10th 2025 edited
     
    Posted By: Peter_in_HungaryI have a bathroom wall (limestone / rubble) that has a 100 mm difference top to bottom. The top leans out from the bottom by 100 mm. The wall is about 70 cm thick, 2.7M high, quite stable and an outside wall, I think it was just built that way.
    I'm confused. Reading the above the top of the wall leans out, but everywhere else it sounds like the bottom of the wall leans out (which would be more natural, I think). Which is it?

    And what is the wall made from? Is it raw brick/block/stone/whatever. Or is there something (plaster?) already on it?

    Why does the finish have to be tiled? Why not use a panelled finish, with whatever is required behind the panels to make them vertical?

    edit (bl**dy auto-whisper :( )
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      CommentAuthorfostertom
    • CommentTimeSep 10th 2025 edited
     
    You could hang tapering vertical battens from the roof structure, more like 70x50 studs at the top, tapering downward to the point where thick plaster can take over.
  6.  
    Wot Nick said !

    The tile backer boards here are made of XPS with a surface coat of mesh-reinforced cement. They can be stuck on with dabs of adhesive or expanding foam (continuous beads better) and absolutely won't come off! Can also be used as lightweight insulating waterproof substitute for plasterboard, if covered with something fireproof.

    Brands are Jakoboard or Marmox Multi board, maybe available with you or something similar?
    • CommentAuthorrevor
    • CommentTimeSep 11th 2025
     
    You could use gyplyner or similar. Other systems are available. A metal framing system bracketed off at the top and part way down to form a vertical partition. If it is to "thick" at the bottom for you, then stop short of the bottom and do that in a more conventional way. You can attach a variety of boards to the frame work.

    https://www.british-gypsum.com/Systems/wall-linings/gyplyner-single
    • CommentAuthorGreenPaddy
    • CommentTimeSep 11th 2025
     
    to add to Nic & WiA, if you wanted a few mech fixings, there are metal washers for this system that fit over screw heads, to give a surface load spread, but slightly bed into the boards as they compress. A few of those would do no harm, since the wall leaning out the way from vertical means the internal additional build up will be at the top.

    A couple of links as examples of boards and washers. No idea what is/isn't avail in Hungary.

    boards
    https://www.protilertools.co.uk/product/premtool-xps-tile-backer-board-1200-x-600mm--choice-of-size-

    washers
    https://www.protilertools.co.uk/categories/tile-backer-boards/backer-board-washers
  9.  
    Thanks all
    It looks like backer boards are the way to go. Rendering from floor up to 5 cm thick then backer boards up to the ceiling with foam fixing.
  10.  
    Posted By: tony?

    The wall is out of plumb. A line dropped from the top touches the wall at the bottom and has a 100mm gap at the top.
    As suggested above the plan now is to render from bottom up until the render is 5 cm thick (the top part of the render will be in 2 layers) after that backer board will be foamed on (2 layers at the top where 100mm needs filling).

    Supplementary question, when foaming boards on to walls how are the boards kept true and level when the foam is trying to expand pushing the boards out of line ?
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      CommentAuthordjh
    • CommentTimeSep 13th 2025 edited
     
    Posted By: Peter_in_Hungary(2 layers at the top where 100mm needs filling).
    Why? Why not fill the gap behind the backer board with foam?

    Supplementary question, when foaming boards on to walls how are the boards kept true and level when the foam is trying to expand pushing the boards out of line ?
    Use mechanical fixings as well?
    • CommentAuthorGreenPaddy
    • CommentTimeSep 13th 2025
     
    PiH, here's how I would go about it, in case any help...

    - fix a vertical straight edge, touching at the bottom of the wall, giving a physical limit line.
    - use what ever form of rigid insulation board you want, say 25mm or 30mm thick being a standard dim. Adhere the first layer of 25/30mm onto the wall, so that it covers from the top, down to say 1/4 of the way from the top, with extra foam at the top, to bring the board towards vertical.
    - add another layer ontop once the first has cured, again from the top of the wall, down say 1/2 of the way, again adding a bit extra foam to bring it to vertical.
    - repeat a third time, covering down 3/4 of the wall, which should more or less be totally touching the plumb line.
    - add a forth final layer of the 10/12mm backer board, running from top to bottom completely covering the wall and previous layers.

    That gives you a fully insulated wall (if only 10mm at the very bottom), will be nicely plumb, and a really good fixing surface for the tiles.

    Use adhesive foam, NOT expanding foam. Apply the foam to the board back, and let it cure for a couple of minutes. If you put in onto the wall straight away, the foam just collapses like shaving foam. Support the bottom of the board from the floor with a timber, to keep it in place. Maybe set another timber leaning against the board, to push it onto the wall, if you see it starting to move out, but the foam doesn't really expand, so you shouldn't get much force pushing the board out.

    The adhesive foam sets in 10 minutes, so can go onto the next layer quite quickly. Only the last board is very important for plumbness. Use the fixings with washers for that last board, but don't fix them tight. Just enough to hold the board, or perhaps a tweak to pull it in to plumb as required. Tighten them up later once cured.

    I also use this sort of approach on floors, adhering the insulation boards, then a chip board adhered on top, altering pressure to it to give level.

    Good luck with whatever approach you use.
  13.  
    Fixing foam doesn't expand as much as ordinary gapfilling foam does. Lay the board down, spray on a bead of foam all round and wait several minutes (4 or 5) for it to stop expanding and go tacky on the surface. Push it against the wall and it stays put!

    Can't directly mech fix them until the foam has gone hard, because the fixing has to compress the board against the foam enough to bury the washer into the surface.

    However being a rank amateur I did fix a couple of temporary battens across the face of my boards while the foam set, to make sure they lined up and stayed true. I put a couple of temporary fixings through these into the wall. Pros will probably have greater faith than me!

    (Edit: cross post with GP)
    (Further edit: there are 20000 you tube channels about this kind of thing)
  14.  
    Thanks both - I will report success when done (hopefully not failure)
    • CommentAuthorrevor
    • CommentTimeSep 13th 2025
     
    It is quite difficult to get all the boards even with using adhesive foam even spraying same quantiy on each board leving it to foam for same time between boards before fitting to wall and that is when the wall is plumb. I would batten out with gypliner and mechanically fix dead true. The drill holes in the panel and fill with foam. It rquires a lot of skill and experience to fix boards with adhesive foam. Good luck
  16.  
    I would like to jump in here if I may as I have exactly the same problem. My wall is a sandstone and cob mix and is out by around 70mm. I wanted to use the same idea that has been suggested for levelling, but I was worried that backer boards are usually an XPS core which would mean it was not breathable. Is it being suggested that there are gaps between the boards allowing the lime plaster to breath.
    • CommentAuthorrevor
    • CommentTimeSep 14th 2025
     
    I EWI a stone wall in Kingspan K5 which is not breathable. The stone was previously cement rendered and pebble dashed and was evident when the render was removed the stone behind was damp as the render had fine cracks in it. Rain got driven in and got trapped. I levelled the wall with lime mortar battened out, insulated, left a gap and cedar clad. The wall cannot get wet now the cladding being a rain screen. My concern would have been retention of moisture in the wall. A conversation with a building expert where I put to him that if one surface i.e in this instance the interior of the wall was breathable wouldn’t that be ok. I had an affirmative reply. Interior wall originally cement rendered as well and plastered over, was lime plastered and painted with clay paint. This was done about 10 years ago and there has been so sign of any moisture in the walls. So if the wall can breathe at least one way that is ok from my experience.

    If doing an internal wall in the way that is being suggested in the postings here would it not be prudent to install a vapour barrier to avoid ingress of internal moisure?

    (As an aside when we bought the house it was advertised as having been upgraded with new wiring plastered out and pebble dashed. Previous owners had a LA grant to improve the property and was overseen by building control. How on earth they did what they did defies belief.)
    • CommentAuthorBeau
    • CommentTimeSep 19th 2025 edited
     
    I've done quite a few out of true wall here with some running out over 100mm. I just use treated 2x1 batten held back with adjustable screws like these

    https://www.efixings.com/adjustable-screws-tx-flat-countersunk-zinc/?variant=23364&srsltid=AfmBOooF-o1XuNOa12rnfjTu4yzwlg_M1VDbAF_dL_m69w4eq44u2UMZLBI

    If there is so much damp the battens are going to rot I'm not sure you want to trap that moisture in regardless of the system used
  19.  
    The wall concerned is 150 years old and limestone/rubble. It is damp, why wouldn't it be with no damp course. I want to avoid battens because the wood will get damp and so eventually will be a problem. The outside will have EWI (opentherm EPS) so should breath, the inside will be tiles because it is a rental property so any surface has to be robust and care free. The area of concern is about 2m x 2m. current plan is to render up to 6cm thickness of render then use a combination of xps and backer board sandwich fixed with adhesive foam.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 1st 2025
     
    Gareth J, your post is a private Whisper to yourself. I can for some reason see it, as you intend, but it seems most people can't.
    •  
      CommentAuthordjh
    • CommentTimeOct 1st 2025
     
    Posted By: fostertomGareth J, your post is a private Whisper to yourself. I can for some reason see it, as you intend, but it seems most people can't.
    Something very weird is going on if you can see these whispers, Tom.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 1st 2025
     
    Yes I'm watching you Dave

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