Are they flat enough....

[k13wjd]

Hi guys, first post here, so go easy. Im doing a full rebuild of my bathroom ( at the same time as installing a central heating system)

The old tiles got removed, as they were a tad "wonky" and old fashioned. Under the tiles i found nasty 50 year old plasterboard, with holes and all sorts. Problem is its paramount - so no studs to screw to.

New 9.5mm boards have been put up, secured by various methods - Expanding foam, Gripfill, Dab+Dot......

My problem is that the biggest wall, ( 2.4m tall, 2.2m wide.) isnt flat.

The centre of the wall is around 10mm futher out from the edges....its fairly gradual, and isnt linear up the wall. I.e its around 3mm at the bottom, 6mm at the top, but 10mm in the centre.

How much of a problem does this cause for a tiler ( i'll be employing one, My tiling is as bad as my plastering !)

Thanks in advance.

[Dave]

Hello and welcome.. we always go easy..

A tad worried about your board fixing methods.. and the boards should really be 12.5mm thick rather than 9mm handy boards.

[k13wjd]

well, Dab+ dot would have been my first choice, But a local plaster told me to try usink SIKA expanding plasterboard foam. Worked out to expensive - and wasnt't all that easy. The board moved off the wall about 5 mins after pressing it there.


The boards won't go anywhere - theyre pretty well held in position.


Also, re 9mm over 12.5......I was told that its better to use 9mm if i was leaving the old plasterboard up...which i had no choice but to do.

I'm dreading someone telling me to remove the board. The foam stuff is seriosuly sticky.

[Dave]

what size tile are you installing.?

[k13wjd]

yet to be decided. I'm hoping for big ones - I just need to convince the mrs.



Whilst i'm here, anyone ever used "niro granite" floor tiles. black polished porc. 600x300.

[Dave]

If you require large tiles then really the walls should be flatter than that.. but not sying it can not be done.. you are best speaking to who will install then first.

[k13wjd]

If you require large tiles then really the walls should be flatter than that.. but not sying it can not be done.. you are best speaking to who will install then first.

Nice one. If the worst comes to the worst, i dab and dot another sheet on top, making sure its spot on. total cost=£20 !


Now, where is that hammer, i still have tiles to take off. damn this house.

[kilty55]

Nice one. If the worst comes to the worst, i dab and dot another sheet on top, making sure its spot on. total cost=£20 !


Now, where is that hammer, i still have tiles to take off. damn this house.

this isnt sounding too good,your trying to over board the plasterboard in the 1st place because its in poor condition,by fixing the new boards wit various methods and adhesives etc and then another sheet of boards on top followed by heavy tiles to be honest this could well come back to haunt you,

[k13wjd]

this isnt sounding too good,your trying to over board the plasterboard in the 1st place because its in poor condition,by fixing the new boards wit various methods and adhesives etc and then another sheet of boards on top followed by heavy tiles to be honest this could well come back to haunt you,

let me clear this up. the 2 sheets that arn't quite right are the ones done with expanding foam. All my dab+dot ones are fine and dandy.

removing the old plasterboard to replace with new simply is not possible...Paramount walls are 2 sheets of plasterboard, 1.5 inches apart, with very stiff cardboard lattice between them. The hole lot is then bonded together. splitting one sheet off without breaking the one on the other side is near impossible.

Even when we had a flood last year, and the insurance comapny came out to fix 4 walls, ( 20m2 total) they ended up dabbing new sheets over the old ones, as removing them would mean building new stud walls ( pretty much rebuilding my downstairs !!!!


the sheet that is bonded with foam is going nowhere, its absoloutly solid. i'd dare say its a stronger bond that dabbing !

[Scott]

The sika foam isnt strong enough for tiling onto in my opinion. I have used it a lot but not for tiling onto.

Personally, Id pull the board off and dot and dab new 12.5 onto it with board adhesive. With this method you would also be able to straighten the wall a the same time.

Alternativlely, and this is a bit more daring you could pul the sheet off and cut out the squares of paper. There should be a stud at the top of the wall t fix to and you should also be able to get a fixing in the floor. You can then add horizontal studs and noggins to these and bond them (grip fill) to the other sheet.

Edit: just read your post

[Onlinetiler]

The expanding foam is pretty strong stuff and I'm sure it will do the job, for future ref if you stick a dozen screws with washers in each board it stops it expanding unevenly.

If you go for smaller tiles and lay them in a traditional square manner, either portrait or landscape they should adopt the contours of the substrate and you may get away with it. If you decide to go brickbond that will become harder as the corners tend to poke out.

The larger the tiles get then the harder the job becomes as they don't 'bend' with the wall as the smaller ones do. The worst case scenario is large format rectangles set brickbond as you'll have to use your highest point as the level for the whole wall - in your case having up to 10mm behind some of the tiles which is beyond the bed recommended by most adhesives and makes the job a lot more fiddly for your tiler. If you want this option I would suggest putting a skim coat of plaster on first to make it level, wait a month for that to cure and then crack on.

Bear in mind the idea is to get over 90% coverage of adhesive on the back of the fixed tiles, that's more likely with a flatter wall.

[kilty55]

k13w,i wasnt having a go at you,you came here looking for advice and thats my advice on it,i would take scottletys route if its possible and re dot and dab one sheet of 12.5 mm boards over your existing old ones,the thought of 3 layers one being fixed with various methods just doesnt fill me with confidence thats all

[k13wjd]

yeah, i know you weren't having a go mate - i do appreciate everyones input. The internet is a brilliant tool for this kind of thing.

I dare say i could get the 9mm sheet thats bonded on ATM off fairly well, old hacksaw blades cut through the foam behind it very very well.

Only thing is, then i'm left with a wall covered in hardened foam, which won't come off in a hurry. Dab+dot onto the foam ?? doesnt sound fun.


maybe i need to wait and see if the tiler can overcome it.


as for the plaster idea....I can't be waiting a month for a skim of plaster to cure - thats out of the question. i've got a full central heating system to install ( diy), a whirlpool bath, fitted vanity unit, false roof of some kind.....and trying to keep within a budget !!!!

Tiling is the only thing i'll be employing someone to do, because getting the tiling right makes a bathroom.

[Dave]

As long as you don't go daft with heavy tiles.. then i think it will be fine..

please make sure your tiler uses cement based adhesive to cope with bed depth sorting the wonky walls out..

[k13wjd]

tell you what, lets cut the jibber jabber. I'll go take some photo's of the issue after tea, and post them here. Check back later guys.

Once again, thanks for the input. I can plumb a central heating system ( i hope) But i tried tiling once, destroyed a pack of 6 tiles trying to cut one in half, and then gave up. I swore never to do it ever again.

[Dave]

pics..... yeh!!

[k13wjd]

ok ok, i'll do it faster.
Ok, first 3 are pics of the walls i have to deal with.....



The first wall i've EVER made - dead on 90 degrees. Forms a gap for my bath, and also forms a new cupboard on the adjoining room

This photo shows a pre-empt for the next photo's - just to show you where the photos are taken.

where the boards join - around 5mm.

and then the dreaded problem. These 2 show the drop at each end of the 1200mm board - around 10/11mm at each end.


Seems the board is high/curved in the middle. My guess is the foam expanded after i put the board on the wall.
Oh, and yes, those are cast concrete floors, Just to add to my problems.

[Dave]

Jesus..

I think you need to replace that one wall... i wouldn't be happy to tile to that... but as they say and onetiler says we are a trade of moaners.

[k13wjd]

if you are telling me to remove the board, then thats what i'll do - after all i came here for advice.



i'm just not sure how well the foam will come off underneath it.....i guess there is only one way to find out right ?

[Dave]

Flat walls are the objective .. and 4/5mm then no probs but that is quite a bit.. and if you want big tiles then it is very wise to replace it IMO.

[Scott]

The foam will come off ok with a bladed scraper and a bit of elbow grease

[k13wjd]

well i'm now a broken man.

the sheet and a half are now in a box. And i'm going to kick myself if the outcome is as i fear. Photo's shortly...This could have been the biggest waste of a plasterboard in the world.

[k13wjd]

oh god, i fear i'm about to be morally destroyed in public.

I've removed that wonky board, along will all the foam ( harris 5inch blade did a nice job, Freshly sharpened on my oilstone!)

Please will someone confirm to me that these walls are NOT ready for tiling. I will say they are 100% true, vertical and horiz, both panels, top and bottom.

Obviously i would have to fill the big holes, with whatever is to hand...I've got pleanty of small peices of plasterboard, i could cut +patch.



Have i just wasted several hours of my life, caused 2 domestics, and chiseled my arm for nothing?. I seriously hope not. I swear the wall looked worse before i put the board up. i look at them now and think....why did i put that board up again?

[doug boardley]

those walls are definitey NOT reay for tiling

[k13wjd]

Thank god for that....Glad my brain served me right for one.

Wish i'd just used D+D to begin with, as at least i could adjust the boards until i was happy they were level.

[Dave]

you will get there and she will love you for it in the end..

[deanotile]

The expanding foam is pretty strong stuff and I'm sure it will do the job, for future ref if you stick a dozen screws with washers in each board it stops it expanding unevenly.
If you go for smaller tiles and lay them in a traditional square manner, either portrait or landscape they should adopt the contours of the substrate and you may get away with it. If you decide to go brickbond that will become harder as the corners tend to poke out.
The larger the tiles get then the harder the job becomes as they don't 'bend' with the wall as the smaller ones do. The worst case scenario is large format rectangles set brickbond as you'll have to use your highest point as the level for the whole wall - in your case having up to 10mm behind some of the tiles which is beyond the bed recommended by most adhesives and makes the job a lot more fiddly for your tiler. If you want this option I would suggest putting a skim coat of plaster on first to make it level, wait a month for that to cure and then crack on.
Bear in mind the idea is to get over 90% coverage of adhesive on the back of the fixed tiles, that's more likely with a flatter wall.

the only thing with putting a skim coat on the boards is the weight issues the large format tiles will probably exceed the 20kg limit for skimmed walls.

[tommyzooom]

Remember, it's all in the prep'
I wouldn't of been happy to tile on that wall before, a bent wall is one thing, but a wall that has been pushed away from the wall beneath by expanding foam is another. D and D 12mm over that and you will be laughing, and not restricted to small tiles either.
Good luck

[k13wjd]

is 12mm REALLY that much better than 9.5

i only ask because i have 5 sheets of 9.5 and zero sheets of 12.

Getting board back to my house is a pain.

[k13wjd]

and whilst im here, given the state of the wall, i presume drywall adhesive will stick well enough???? i'm not a plasterer, but grasp the basics.

i also presume that it would be sensible to mix the mud slightly thicker to help it stick to that dilapidated paper on the wall ?