board or plaster?

[largerjt]

Hi guys i hope someone can help me out here.

I've just started to do my bathroom and whilst trying to get the tiles off 95% of the plaster is coming off to, so i'm down to the bare internal wall. i was going to have it re plastered then tiled but a friend of a friend has suggested to just board the whole bathroom and then tile straight onto the board.

can this be done? how would i stick the board to the wall?

in my opinion i think i would get a much better result for the tiler as the wall should come out very flat, am i wrong in thinking this?

any help you can give would be much appreciated.

Rob

 

[Richard C]

The process of putting plaster boards onto a wall is called dot & dab; do a search, there are loads of archive posts. I wouldn't use ordinary PB if you’re not skimming, particularly in wet areas – behind the bath or in a shower enclosure. You can get moisture resistant PB which is fine for general bathroom areas but I still wouldn’t use this in wet areas. Even waterproof tile cement/grout is porous & if water gets into the PB behind, it will disintegrate. I always use Aqua panel in such areas but others on here prefer to use PB & tank the entire area with a water proof membrane & then tile over that; again there are archive posts on this.

 

[GJS]

I was in this same situation and, as Richard says, I dot & dabed moisture resistant plasterboard (the green stuff). I used it on the wet areas as well. The problem with aquapanel is that there is no adhesive that's recomended by the manufacturer to dot and dab it. It's supposed to be screwed to battens. There were no problems for a year but then I moved house so I don't know how it held up long term.

Dot and dab is quite easy. The advice I would give is that you must have the adhesive really thick. If it's too thin the board will just go flat against the uneven wall. There's a good video on the Knauf site.

Brush off any loose material from the wall with a wire brush and paint on one coat of 1:5 diluted PVA and allow to dry before starting.

 

[Richard C]

The problem with aquapanel is that there is no adhesive that's recomended by the manufacturer to dot and dab it. It's supposed to be screwed to battens.

One way of doing it without battens is to use a few dabs of Drywall to hold the Aquapanel in place & then use through fixings straight into the wall.

 

[noseall]

One way of doing it without battens is to use a few dabs of Drywall to hold the Aquapanel in place & then use through fixings straight into the wall.

i subscribe to this method too, because it is fast, effective and easy.

 

[largerjt]

hi, hanks for your replies, sorry if i sound completely stupid but what do you mean by a few dabs of drywall?

thanks again

Rob

 

[Richard C]

Drywall Adhesive; it comes in bags in powder form & you mix it with water to form a paste which you then dot onto the wall (I use a large wooden kitchen spoon) & stick the board to it; it's normally used on plasterboard or coving but in this case used to initially fix the Aquapanel before securing with through fixings.

 

[GJS]

One way of doing it without battens is to use a few dabs of Drywall to hold the Aquapanel in place & then use through fixings straight into the wall.

Hmm...that's not a bad idea.

 

[largerjt]

should i just use normal screws to fix to the wall or do i need something special?
thanks

 

[Richard C]

No, you need to use through fixings; they look similar to this;

http://www.screwfix.com/prods/96876/Fixings/Frame-Fixings/Fischer-FUS-Frame-Fixing-10x60

With this type of fixing you just drill the hole through whatever your fixing into the wall behind, push the screw & integral plug through into the wall & tighten it up. No need to take whatever your fixing down from the wall to fit a plug. Any merchants should have them but B&Q also sell them; obviously make sure the fixings you buy are of suitable size/length!
plug

 

[johnheritage]

Digging it up from the grave.

Thanks for the thread, I'm doing the aquapanels in the bathroom right now and found it handy to have some experienced advice to back up the plan.

I used a fair bit of DnD on each.

I decided not to do the fixings until it had gone off, as I am using corner toilets and sinks and didn't want to knock the corners off square. But it probably would be best to get them in just as it starts going off, as I found one panel had crept a little out of flat with the MR boards.

I can make a suggestion, mix it so it's pretty thick, as the runnier mix doesn't grab tightly enough (it'll hold them, but you'll find the boards drift out as they sag away from flat / plumb / square).

I thought they'd be a major pain to cut (I bought a diamond daisy disc for the grinder to be sure), but a coarse tooth handsaw was fine. Really clean cut, very little dust, almost no sawing effort and the saw had already had most of it's teeth wrecked by the builders (it's one of their's for doing blocks).

In a lot of ways, it's easier to work with than PB.

I'll be SBR tanking on top of the panels.

The house is from the 1920s and the walls / batons are in a twisted way. Couldn't get it all out with the boards, so I may skim some or all of it with some browning first to get the last few mm flat and make it easier for the tile adhesive.

SBR can be painted on raw (like watery paint) for a thin barrier, more layers can go on and it can also be used as an admix for renders / screeds / 'stuff' (plaster), giving it better flex and making it better at repelling moisture.

 

[1john]

You can also cut them with a stanley knife same as plasterboard and then surform the edge.

 

[Richard C]

Saw or Stanley knife as with ordinary PB will do it, blades blunt very quickly though

I'll be SBR tanking on top of the panels.

I assume you mean SBR primer, not tanking per say? Don’t prime the tile base unless the addy manufacturer recommends it; most don’t. If your tiles are larger than 300 x 200mm use a quality trade cement addy; flexible over boards.

The house is from the 1920s and the walls / batons are in a twisted way. Couldn't get it all out with the boards, so I may skim some or all of it with some browning first to get the last few mm flat and make it easier for the tile adhesive.

Two things to watch here; base gypsum plasters are not suitable as a tile base (except Dri-Coat) so don’t tile over that. Finish plaster also restricts tile weight to 20kg/sqm (including 2-4kg of addy) which could be a problems with large format tiles. One method is to use cement tile addy to fill out & level, you can tile over that the next day.

Knauf say you can’t plaster Aquapanel except using their expensive “special” plaster. I’ve used Aquapanel with edge beading to form small services access panels & successfully skim these but you have to PVA prime 50:50 2/3 coats & leave it to dry off for at least 25 hours.

SBR can be painted on raw (like watery paint) for a thin barrier, more layers can go on and it can also be used as an admix for renders / screeds / 'stuff' (plaster), giving it better flex and making it better at repelling moisture.

Fine for renders, screeds etc but I would not advise using it on a tile base. To reiterate; you should only prime where addy manufacturer recommend it. Priming will affect both initial & even final adhesion strength which, again, will be a problem with large format tiles; it will also invariably invalidate the addy manufacturers warranty. If you need/want to tank, your far better off using either a proprietary waterproof membrane or liquid membrane Dunlop or BAL WP1 as these will accept tile weights of 30kg/sqm +.

 

[johnheritage]

Nice one Richard!

{edit}Forgot to ask, I didn't have any of the special ceramic screws handy for the panels (I was doing them at about 11pm and the noise complaints were starting) so used standard blacks for the PB.

I've only had to screw one panel to timber and had a quick google first to check, but I have been looking at them and wondering if the cement based board is going to rot through those over time.

Are the yellow passivated screws a better or worse idea? Or is there something else I could use other than the ceramics?

Since it's only one board, and it'll only be two when it's finished (tonight probably), putting another handful of screws in per board isn't a problem.***

I have read your other post about the push thru anchors and will be using them over the DnD, but figured they're isolated from the cement by the plastic plugs, whereas the ones direct into the timber have the metal touching the cement.

***Unlike boarding the ceiling, and watching my brother walk back down the ladder and let go of the board with two screws in it at my end. SNAP. He's 6ft 2, 13 stone and does weights, yet wussed out after 60 seconds holding it. Can't get the staff!

 

[Richard C]

I wouldn’t be overly concerned about the steel screws reacting reaction with cement; I have used ceramic screws in the past by I only ever use standard phosphate coated drywall screws now.

My wife has helped me fix full size 12.55mm ceiling boards quiet a few times, it’s more to do with knack than muscle; some even manage it on their own with a board prop.