Moistureboard or Cement/Aqua Board?

[sergeantash]

I am currently decorating my bathroom and have stripped the walls back to the 'Ash Block' (see here for more information on the wall type //www.diynot.com/forums/viewtopic.php?p=1595298).

I am installing a Shower Bath - the wall of the room where the shower is installed needs boarding as most of the room except for this wall are plastered.

My question is whether I can get away with Gyproc Moisture Board or should I use Cement Board? I am planning on tiling over the board and using BAL waterproof primer and adhesive.

Appreciate your help!

 

[Richard C]

If you use MR board, I would advise you tank but, personally, I would go for a decent tile backer board. What do you mean by BAL waterproof primer? Which BAL adhesive are you intending to use? What size/weight are your tiles?

MR board must be primed if you intend plastering.

 

[sergeantash]

Sorry to be stupid but I'm not sure what 'tanking' is unless you mean sealing the board?

The tiles are fairly large, I don't have a specific size to hand but they're approximately 1.5ft x 3/4ft and of a standard thickness, 6mm?

Apparently the Aquaboard is a decent tile backerboard, the most important element of course being that it is naturally waterproofed/moisture resistant, hence why I'm considering the above two.

I'll buy a suitable BAL adhesive depending on the final choice of board.

 

[Richard C]

I'm not sure what 'tanking' is unless you mean sealing the board?

This is a tanking solution;
http://www.bal-adhesives.co.uk/products/wp1-coating
This is the kit which includes tape & solution;
http://www.bal-adhesives.co.uk/products/waterproofing-kit
or you can use a tanking membrane.

The tiles are fairly large, I don't have a specific size to hand but they're approximately 1.5ft x 3/4ft and of a standard thickness, 6mm?

450 x 700mm aren’t tiles, they’re paving slabs ! Is that right ? You need to check the weight/sqm; unplastered plasterboard will accept up to 32kg/sqm but plastered, this reduces to 20kg/sqm including adhesive & grout. For tiles that size, I would forget plasterboard & only use a cement tile backer board. If you’ve not tiled before, such large tiles are going to be a real challenge for you to hang & look good; the largest tiles I’ve ever hung is 600mm x 300mm.

Apparently the Aquaboard is a decent tile backerboard, the most important element of course being that it is naturally waterproofed/moisture resistant, hence why I'm considering the above two.

Are you referring to Lafarge Aquaboard? If so it’s not a tile backer board, it’s a Gypsum based moisture resistant plaster board, of similar specification to British Gypsums MR plaster board; if you use either of these, it should still be tanked. Knauf Aquapanel is a cement based tile backer board but there are others.

I'll buy a suitable BAL adhesive depending on the final choice of board.

The size weight of the tiles rather than the boards is more relevant to the adhesive you need; for large heavy format tiles, you will need a flexible cement powder adhesive;
http://www.bal-adhesives.co.uk/products/rapidset-flexible
& a flexible grout;
http://www.bal-adhesives.co.uk/products/microflex

 

[sergeantash]

http://www.bal-adhesives.co.uk/products/wp1-coating
This is the kit which includes tape & solution;
http://www.bal-adhesives.co.uk/products/waterproofing-kit
or you can use a tanking membrane.

Yep thats the stuff, thats what I mean't by sealing the board - BAL seems to be the stuff to have!!

The tiles are fairly large, I don't have a specific size to hand but they're approximately 1.5ft x 3/4ft and of a standard thickness, 6mm?

450 x 700mm aren’t tiles, they’re paving slabs ! Is that right ? You need to check the weight/sqm; unplastered plasterboard will accept up to 32kg/sqm but plastered, this reduces to 20kg/sqm including adhesive & grout. For tiles that size, I would forget plasterboard & only use a cement tile backer board. If you’ve not tiled before, such large tiles are going to be a real challenge for you to hang & look good; the largest tiles I’ve ever hung is 600mm x 300mm.[/quote]

Sorry I have misrepresented the sizes a little, I don't have the tile's to hand but on second thought, I'd say they're about 260mm x 400mm, not sure of the weight but they seem about average for a tile of that size.

The walls that don't need 'sorting' are regular plaster on top of concrete/brick and so shouldn't pose a problem, its just this single wall that backs onto the shower bath that I'm worried about.

Are you referring to Lafarge Aquaboard? If so it’s not a tile backer board, it’s a Gypsum based moisture resistant plaster board, of similar specification to British Gypsums MR plaster board; if you use either of these, it should still be tanked. Knauf Aquapanel is a cement based tile backer board but there are others.

Yep thats the stuff, LaFarge - haven't heard of Knauf but I'll check that out on the way home tonight.

Then there's the question of whether I dot/dab the chosen boarding or attach to batons - the problem being that the wall in question is only just 2inch thick and I don't want to shrink the bathroom anymore than it already is (70" x 86") - apparently concrete boards cannot be dot-dab'ed, only batoned.

 

[Richard C]

Yep thats the stuff, thats what I mean't by sealing the board

What your referring to is tanking.

- BAL seems to be the stuff to have!!

I only use BAL but there are others equally as good, just avoid the cheapo DIY products most sheds stock; although B&Q now stock Mapei which is good.

Sorry I have misrepresented the sizes a little, I don't have the tile's to hand but on second thought, I'd say they're about 260mm x 400mm, not sure of the weight but they seem about average for a tile of that size.

They are still relatively large tiles so I recommend you use a flexible powder cement adhesive not tub mix.

Yep thats the stuff, LaFarge

It’s not a tile backer board, it’s just a Gypsum based, moisture resistant plaster board.

- haven't heard of Knauf but I'll check that out on the way home tonight.

Knauf make Aquapanel (available from Wickes) which is a cement based backer board; other tile backer boards are available.

Then there's the question of whether I dot/dab the chosen boarding or attach to batons - the problem being that the wall in question is only just 2inch thick and I don't want to shrink the bathroom anymore than it already is (70" x 86") - apparently concrete boards cannot be dot-dab'ed, only batoned.

Not recommended by the manufacturer but you can dot & dab the panels to the wall in the usual way. Make sure you know exactly where the adhesive dots are (use a 200 x 200mm grid pattern) & once the panel is fixed & the adhesive has gone off, mechanically fix the panels to the wall using suitable length through fixings (frame screws) on the same 200 x 200mm grid pattern. The screws must pass through the panel & the adhesive dots into the wall or the panels will crack when you tighten the fixings.

 

[sergeantash]

Not recommended by the manufacturer but you can dot & dab the panels to the wall in the usual way. Make sure you know exactly where the adhesive dots are (use a 200 x 200mm grid pattern) & once the panel is fixed & the adhesive has gone off, mechanically fix the panels to the wall using suitable length through fixings (frame screws) on the same 200 x 200mm grid pattern. The screws must pass through the panel & the adhesive dots into the wall or the panels will crack when you tighten the fixings.

Thanks for this, sounds like a perfect solution as it won't then shrink the room substantially! With Dot/Dabbing, do you also run a line of Driwall Adhesive along the borders of the board, then dot in the inner area as you suggested in 200x200mm grid patterns?

 

[Richard C]

You could put in an intermediate dot but it’s not as important with the cement based board as it is much stiffer than plasterboard; the screws provide the mechanical integrity.

Many seal between the board edges with silicone but I don’t as not much sticks to silicone; spread too much of it about & you may start having problems with adhesion. Knauf make a sealant specifically designed for this but immediately before tiling, I fill the joint with a light skim of tile adhesive & tape the joins with glass fibre reinforced joint tape. Make sure you plan your tiles & board joints so they overlap, don’t let the two coincide. Run a bead of silicone around the bath (fill it with water first & leave overnight) & down the corner wall joint rather than rely on grout; use flexible grout everywhere else.

 

[sergeantash]

You could put in an intermediate dot but it’s not as important with the cement based board as it is much stiffer than plasterboard; the screws provide the mechanical integrity.

Many seal between the board edges with silicone but I don’t as not much sticks to silicone; spread too much of it about & you may start having problems with adhesion. Knauf make a sealant specifically designed for this but immediately before tiling, I fill the joint with a light skim of tile adhesive & tape the joins with glass fibre reinforced joint tape. Make sure you plan your tiles & board joints so they overlap, don’t let the two coincide. Run a bead of silicone around the bath (fill it with water first & leave overnight) & down the corner wall joint rather than rely on grout; use flexible grout everywhere else.

Thanks again for the brilliant information. Just been to B&Q and bought 3 sheets of Aquaboard (concrete board), I have dot-dab'ed standard Gyrop plasterboard before but unsure whether I did it right, have you a good guide including how hard you actually press the board to the wall once you offer it up? Unfortunately the three pieces will have to be mounted stacked to cover the height of the bathroom - should I set the first piece level, wait for it to set, screw-secure it (as you mentioned above) and then fix the boards above a few days later using the first board as a guide?

Thanks again for all your help!

p.s. when securing the board with screws, should I rawlplug too?

 

[Richard C]

I have dot-dab'ed standard Gyrop plasterboard before but unsure whether I did it right, have you a good guide including how hard you actually press the board to the wall once you offer it up?

How hard do you push! Hard enough for the adhesive to grab & to get the boards level but cement based boards being very stiff will self level to a certain extent. If you’ve dot-dab'ed before you will know that you control the stand off by the size of the adhesive dots you use, depending on how level the wall is, if the wall is fairly flat, you can board it tight.

Here’s a couple of guides to D&D;
http://www.british-gypsum.com/pdf/SB07_DriLyner_02.pdf
http://www.ultimatehandyman.co.uk/PLASTER_BOARDING_DIREcT_BOND.htm

Strips of adhesive are shown in the British Gypsum guide but for fixing cement board, use dabs every 200 x 200mm as I said & similar to the hanyman guide.

Unfortunately the three pieces will have to be mounted stacked to cover the height of the bathroom - should I set the first piece level, wait for it to set, screw-secure it (as you mentioned above) and then fix the boards above a few days later using the first board as a guide?

Once the adhesive has grabbed the boards should stay put if you’ve done it right; you could leave it, say, an hour between each level to give the adhesive a chance to go off a little but you should be able to board out in one go, certainly in the same day. Don’t fix the boards to the wall until the adhesive has set thoroughly, at least 24 hours.

p.s. when securing the board with screws, should I rawlplug too?

You must plug the wall but using separate plugs is a lot of messing about as you will have to drill the boards, mark through to the wall & then drill the holes first; too much work. It’s easier to use through (frame) fixings, something like this;
http://www.diy.com/diy/jsp/bq/nav.j...refview=search&ts=1272612571047&isSearch=true

 

[sergeantash]

Richard once again thanks for your really comprehensive assistance - I think I have the confidence to give it a go tonight so I'll let you know how I get on!! These boards weigh a tonne, its incredible that a few dab/dobs can support it, plus the nail in screws of course

Thanks again, watch this space!

 

[Richard C]

plus the nail in screws of course

It's a hammer in fixing not a nail screw which is soemthing quiet different so don't hammmer the screw into the plug will you

 

[sergeantash]

plus the nail in screws of course

It's a hammer in fixing not a nail screw which is soemthing quiet different so don't hammmer the screw into the plug will you

Lol whooops, I did buy the right thing in the end (the exact product infact that you linked to), thanks again for the guidance, really appreciate it!

 

[sergeantash]

Just to say a mahussive thanks to RichardC for his excellent assistance with the fitting of this concrete board, I am still unsure why the manufacturers don't suggest mounting the board in this style as it is truly solid and feels like it could support an immense weight!!

Anyway, all done as you suggested and looking brilliant! Thank you once again for your help Rich!

Untitled

• sergeantash
• 8 May 2010
• 1

p.s. I haven't yet fitted all of the upper board's reinforcing frame screws, hopefully sorting those today!

 

[samlauncher]

Appreciate the info, it’s good to know.

Lucky Cement