Is there a minimum thickness for plasterboard when tiling

[Hotwire]

As some of you may know ive recently had a plasterboard wall replaced in my bathroom. The plasterboard was supposed to be 12.5mm thick and have 2 layers either side, but only 2 x 9mm board was used each side. These boards were screwed to the timbers. Im a bit concerned about the thickness of these boards being able to support tiles sized 17" x 12" weighing in at 2.3kg each. In an earlier post i was told that plasterboard with a skim of plaster would support 20kg,s a sq metre but no board thickness was given. Can somebody put my mind to rest over wether this board is going to be up to the task . Thanks.

 

[worpler]

maybe try tileforums.com.....is dedicated totally to tiling questions.

 

[Hotwire]

Thanks i will check tileforums.

 

[Thermo]

it should support it, but contact british gypsum or knauff and they give you all the technical blurb you need

 

[TexMex]

The 20kg/m generally refers to a plastered plasterboard wall. It is a limitation of the bond between the plaster and the board. When the boards have not been plastered (ie tiling directly on to the bare boards), this figure generally rises significantly. Although this would depend on the tile adhesive, a figure of 32Kg/m would be quite normal.

Doing a quick bit of maths on your tiles, they come out to about 17Kg per m. Shouldn't be a problem. Check the spec of the adhesive.

 

[Hotwire]

I gave British gypsum a call and the girl i spoke to said she didnt have any info but she would go and consult colleague. The news wasn't what i wanted to here, she said they wouldnt recommend tiling on it as it may bow. Then advised me i should have used 12.5mm board. The only light that may be at the end of the tunnel is i didn't say there were noggins in the wall and that may have made a difference. Heres the spec for the finished wall as measured by me , it may shed a bit more light on it.

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Thanks for the working out TexMex, the wall though has a skim of plaster.

Im so hacked off with this, nothing ever seems to go smooth.


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[TexMex]

Now the way I see it, the man concern is that the surface board is just 9mm thick. Immediately behind this is another 9mm board. Now if those two boards were bonded together that would be 18mm and very stiff (as plasterboard goes). Since both layers are bonded to the studs, they are already held together there.

Now what I'd be inclined to do is just bosh in some of these things, in an arrangement, similar to below. You wouldn't need the actual screw (as shown in the picture), as you don't need to actually fix anything to the plaster board. You would therefore, be left with the head of the fixing, flush with the face of the wall.

Fixing them in place is also very quick, you just litterally screw them in. With a power driver, you could probably do the whole wall in about half an hour.

 

[Hotwire]

Yeah i get your drift TexMex but i dont fully see how these fixings are gonna be able to hold the two boards together. Ive done a search on the net to see if i could find any technical spec for them as not using them before i cant figure out there length from the pic. Holding the two boards together seems to be a simple way out of a sticky problem though and could be the way to go. Ive just looked on the Knauf site and one of the products is this 9mm board so i will give them a ring and see if they can come up with some more info.

 

[TexMex]

Pop down B&Q, Wicks or whatever and have a look at them. I think you'll find that the threaded part is at least 20mm long. Since these fittings rely on the outside thread (with no extra support) to hold them into the plasterboard, even when you hang something from them, it follows that, if that thread extends into the other board, they will also be firmly anchored into that as well. If you have any offcuts of plasterboard about, buy one and give it a try. I reckon they'll work pretty effectively.

After all, the boards are already pretty secure, you only add put a bit more resistance into the two separate boards parting company.

 

[Hotwire]

Wish i would have read your reply before i went out ive justy passed a B&Q, but theres a diy shop up the road so i will take a look there. Ive rung Knauf this morning and there saying this board is not for timber construction but to be used with metal studs. They didnt have a recommendation for tiling on it saying only 12.5 mm was recommended. Im gonna go and get one of these metal redidriva fixings and see if ive got some of cuts of board to try it on, then im putting everything on the back burner till monday. Seeing as its my birthday today and im gonna take it easy and forget the hassle for a while.

 

[Hotwire]

Hey TexMex, your idea seems good. I gave it a try and it holds those 2 boards tight, dont know if it would stand the test of time but well thought of. The only problem ive got is this was an insurance job using there builders so im gonna contact them and see what they say. I will post the eventual outcome here. Ive also resized my original picture so people dont have to scroll from side to side.