How do I attach multiboard to the wall

[TenaciousJohnny]

Hi,

I am redoing my shower. The plumber has fitted a new shower tray & I am looking to retile the area so the plumber can fit the shower cabinet & shower. The existing tiles were fixed to 10 mm plasterboard. The plasterboard was in turn attached to the (solid brick) walls by blobs of cement which means that there is actually an 11 mm gap between the walls & the back of the plasterboard (21 mm from the wall to the front of the plasterboard).

Removing the tiles revealed that the existing plasterboard in the bottom half of the shower area was very wet & needs replacing. I have cut away a large area of the wet plasterboard & removed the cement attaching it to the wall.

I plan to replace the plasterboard I removed with multiboard. However, I am not sure how to attach it. I need to re-create the 11 mm gap between the wall & the the new multiboard so that it is flush with the plasterboard that doesn't need replacing.

Presumably I need to use the same method as was used before - ie cement the multiboard to the wall? If so, what sort of cement should I use? Do I just put lots of blobs of cement to a depth of say 15 mm & push the board into the cement until I get the multiboard flush with the existing plasterboard? Do I put the cement on the multiboard or the wall?

Any help much appreciated. I have never worked with cement before.

Thanks,

Johnny

[Stuart Noble]

You put the blobs on the board. Plasterboard adhesive is easier because it's lighter and the blobs are more likely to stay in position as you lift the board. Seal the wall with 1 pva: 4 water to be on the safe side. Best to use Aquapanel or similar if it's going to get wet with the new setup.

[Lobster]

Just to be clear, it definitely isn't cement you need here - plasterboard adhesive is different stuff. Having said that, what's multiboard?

I'd agree about using Aquapanel, but it's supposed to screwed to a rigid frame, not dab'n dotted (dot'n dabbed?). And it doesn't sound like the OP has enough clearance to attach battens for it now.

David

[TenaciousJohnny]

Thanks for both of your advice. Ill look for some plasterboard adhesive .

saw multiboard at b & q - was described as water resistant plaster board -maybe the same as aquapanel?

John

[Stuart Noble]

I've used adhesive with it where the board rests on the floor, but it's so heavy compared to PB that the next board up would probably have to be screwed to the wall. I don't think you necessarily need battens.

[Janet Bale]

No it's not the same. It is just what you said above. Aquapanel is much more expensive and not worth using just for patching in existing plasterboard. Plasterboard adhesive is also called bonding. Just dob and dab it on. Use a wettish mix with large dobs and gently push it back to be flush with the rest. You can use a large block of timber to bang it into place but be careful as the adhesive goes off quickly. Paint with PVA before you tile.

Martin

[Stuart Noble]

Bonding isn't pb adhesive. Probably similar but not worth taking the risk.

[TenaciousJohnny]

Thanks for the responses. I have bought some plasterboard adhesive & am going to use that. One more question. I am going to have to use 2 pieces of the multiboard on the wall where the shower is. Do I have to worry about sealing the gap between the 2 pieces with silicon or something? I will ultimately be tiling over the area. TIA Johnny

[Lobster]

No - if any water gets under there later you're stuffed anyway, and if you cover it all with silicon that will dissuade the tile cement from sticking properly. You do want to make sure there's no relative movement between the two adjacent bits of board; make sure both are well supported behind at the edges, and fill the gap with adhesive (now) or tile cement (later).

David

[TenaciousJohnny]

OK - Thanks for that

[Janet Bale]

Tut tut Stuart Noble :-)

I have a large white bag in my garage right now labeled "LaFarge bonding compound - adhesive for plasterboard". It is used all the time in the trade for dot and dab dry lining. I use it myself. Check out the LaFarge website

for loads of good technical info including pictures of how to do it. Yes you can buy general purpose plasterboard adhesive as well but I think it's more expensive.

Martin Noble

[Stuart Noble]

If I go into a BM and ask for a bag of "bonding", that isn't what I'll be given though is it?

[Janet Bale]

Depends on your BM I suppose. When I go in mine they just say "It's in the plasterboard shed mate!" and I have to pick it up myself.

[Stuart Noble]

What, 25 kgs? And you a woman. What's the world coming to?

[Janet Bale]

Idiot! Don't let the family name down Stuart. Last time I looked I was a bloke. I am using my wife's account and if you read my posts fully you would see that I sign them Martin.

Interesting topic for discussion though. How seriously are female posters taken on this DIY forum?

Martin Noble

[S Viemeister]

People have generally been reasonably polite and helpful to me.

Sheila

[Holly, in France]

Aha! So *this* is why that question suddenly appeared. All makes sense now. I've changed the title for othes that might not have cottoned on.

Me too. And so have you to them :-).

-- Holly, in France Gite to let in Dordogne, now with pool.