Tiling on painted/damaged plasterboard walls

Discussion in 'Tiling' started by JasonR, 6 Feb 2011.

  1. JasonR

    JasonR

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    I have stripped the old tiles off around my bath ( only 3 tiles high ), which has pulled off the plaster skim and some of the paper from the board beneath. however not down to the plaster filling. The wall above the tiles was painted, emulsion over various layers of other paint.
    - I'm thinking this isn't the best surface to tile on.

    I plan to fix a mixer shower over the bath with the pipe work concealed in the stud wall. Or that's what I thought. It turn out that I don't have stud walling.

    The walls are made of 3 layers of 12.5mm Plasterboard just stick together. It's been suggesting on some forums that this was how many Housing Association buildings were put up ( much of Hemel Hempstead i'm guessing )

    So what are my options?

    It it possible to strip the top layer of plasterboard off and replace with new. Does anyone know if this is possible?

    As for concealing the pipework - I guess I could channel the pipework into the wall - Possibly fixing a sheet of plywood on the other side of the wall ( kitchen ) to fix shower wall-plate to.

    Any advice would be appreciated. Thanks
     
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  3. Richard C

    Richard C

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    You can tile onto paint but it depends how well it’s stuck on there; stick a a lump of gaffa tape on it & pull it off; if the paint stays put it’s usually OK but it will also depend on the weight of tiles your having; large format tiles are heavy & require the correct tile base if they are to stay up there. If the plaster skim has also pulled off, you will have to fill that & it may not be particularly well stuck on there anyway & you really need to be tanking the shower/bath area if you stick with the existing plasterboard. Realistically, I would rip the lot down & start again using waterproof tile backer boards in wet areas, Moisture Resistant plasterboard everywhere else. If you want to plaster MR plasterboard it must be primed first.

    All things considered, it will probably be easier & quicker to rip the lot off & replace as described above.

    For concealed mixers/shower pipes your better to build a false wall & run behind that. You can channel the wall locally for the mixer valve but it’s not advisable to go any deeper than 30%.

    Check out the tiling sticky & forum archive posts before you start tiling to avoid making costly & time consuming mistakes.
     
  4. JasonR

    JasonR

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    Thanks Richard,

    Tanking has always been the plan, A Dunlop tanking kit is sitting in by screwfix basket.

    Ripping the lot down then stud walling etc is a lot of work ( for me ). And will double the depth of the wall. I guess that moved into the relms of structual work which will require futher permisions from the freeholder. ( It's taken me a month to get where I am now :mad: )

    I've read the sticky thread, and will use this as best practice and best advice.

    I did the sticky test, but the top layer is emulsion and the tape came away with no stick. ( I;ve read it can become 'active' or interact with whatevers put on top) I'll have a go at the wall with a wire bush and see if I can get down to the lower layes which do not seem to be matt.

    The tiles are Istanbul Wall Tiles - Sand - 25x33cm from homebase, Do these constitue Large format tiles?

    The channel only has to go downwards a foot or so, I might consider channeling on the kitchen side and cover with ply wood, and retile again on this above kitchen sink - your advice is good, but limited space might make this impractical.

    I'll investigate further.
     
  5. Richard C

    Richard C

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    Don’t understand what you mean :confused: ; did the paint stick to & come away with the tape or did the paint stay on the wall :?: If the paint is well stuck to the wall (& it needs to be with the tiles your laying) if you score the paint & apply an acrylic primer, the tiles should stick well when using a powder cement adhesive & yes they do constitute a large format tile; I would advise powder adhesive an anything over around 200mm square. If you use tub mix you could have problems getting them to stick initially & even stay on the wall over paint; the adhesive relies on evaporation to dry & set which could take many days. Use a flexible addy & grout over the boards.
     
  6. JasonR

    JasonR

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    The emulsion paint seems powdery, It didn't pull of flakes of paint or anything like that.

    So Assuming I tile on the surface I have. The Dunlop kit contains a primer, ( not sure if this is acrylic ) so slap this on as per instructions. Then the water proof coating.

    Then using a powder adhesive, Does this need a primer on top of the water prrof coaring?
    ( Thinking of using "Granfix Fast set flex" or "Ultra PRO RAPID RS" on the floor - but these may be floor specific. )
    screwfix do Mapei Keraquick, so also an option.
     
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  8. Richard C

    Richard C

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    Should be OK then.

    Yes sorry; if your using the tanking kit just use their primer, that will isolate the gypsum anyway

    Familiar with BAL (which I believe is the same as Dunlop as they come from same company) & with BAL, you don’t need to prime when using either their tub or powder addy but I would advise you check both the Dunlop fact sheet & your chosen addy manufacturer. It’s always advisable to stick to the same manufacturer as their products will always be formulated to compliment each other; if you mix & match there is always a danger something may go wrong.

    Granfix & Mapei are good trade products but I don't have any experience with Ultra Pro. I only use BAL so that’s the stuff I know best but either of the powder based addy’s should be fine, but follow the instructions.

    If you’re tiling the floor, what have you got down there then :?:
     
  9. JasonR

    JasonR

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    I agree about using the same company for Tanking and Adhesive ( That was my plan at one point ). I was going to go with the dunlop Adhesive too, but talked myself out of that.
    BAL does seem to be the most popular - But so many variants to choose from blue/green/white star/Single Part Flexible/...
    Blue star comes in a ready mix, as did the dunlop, at Screfix.

    There are other sources though - More research

    The floor is concrete. The plan is to lay 10mm insulation board. Under floor heating cable from cablewarm ( The only company to have responded to my emails ) And then tiles on top. With some adhesive inbetween. In this case the granfix seemed to the adhesive used by some other Underfloor heating companies.
     
  10. Richard C

    Richard C

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    Again, I would advise not to use tub ready mix, you may live to regret it. Have a read in the archive posts where you will find at least 3 OP’s in the last few months or so asking why the addy wont set & tiles have started falling off wall after 3 days!

    Not sure about Dunlop addy. They where acquired by BAL some years ago so I guess their tanking membrane may well be the same but I’m unsure about their addy range; maybe they have kept the two product lines distinctly different as a pricing/trade-DIY policy. Mapei are also up to “marketing tricks” with the range of products they now sell in BNQ under the “Buildfix” banner which they admit they are not the same formulation as their trade Mapei products; I really don’t get why a company with such a reputable trade reputation would risk it. I only found out by digging around & another OP contacted their technical department which resulted in the beans being spilled!

    Have you looked at Marmox insulation board? You’d do better to put an SLC over the heater mat & tile onto that, if you bed the mat in powder addy, you will find it almost impossible to repair & you could end up with an uneven floor if not experienced.
     
  11. JasonR

    JasonR

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    Point taken on the ready mix. that was probably why I talked myself out of the dunlop. I took the unibond ready mix back for refund weeks ago. (and the general view was it was un fit for porpous )

    What BAL product would you recommend assuming I used WP1 for tanking?
     
  12. Richard C

    Richard C

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    For larger tiles, I tend to use Rapidset Flexible which can be grouted after just 3 hours but it has a rather short pot life (around 40 mins). It works well providing you know what your doing & only mix as much as you can use in, say, 30 minutes to allow cleaning bucket/tools between each mix.

    Single Part Flexible has a longer pot life & can be better for the inexperienced as tiles can be adjusted for longer but must be left 16 hours before grouting.
     
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