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I am installing large ceramic tiles: 300x600 x11mm thick on 12.5mm plasterboard on a stud wall. The wall only has standard spacing for the studs and ideally should have more noggings to support the plasterboard. If I push the plasterboard on the areas where there is no wood behind, it moves a little.

Is using flexible adhesive and grouting the solution to avoid problems with the tiles coming off? If so, any products people can recommend? I guess the plasteboard is not going to come off with sufficient screws fixing it.

If I push the plasterboard on the areas where there is no wood behind, it moves a little.

This needs to be addressed first, or I think your asking for trouble

How do I do this? I do not think it is possible to make plasterboard mounted on stud walls completely rigid unless the stud wall is virtually solid

What distance apart were the studs?

600mm centres. Studs 50mm wide by 75mm deep.

600 is a little wide, although you can get away with that distance.

I'd put some extra dry wall screws in the plasterboard to try and stiffen it up a little.

If you think that there is still too much give in it then you should remove the plasterboard and fit some noggins to be on the safe side, then replace the plasterboard. If it is being tiled over it does not matter about any additional cuts in the plasterboard.

I had a "crazy" idea which I have never seen used in stud walls: Inject PU foam between the plasterboard leaves like they do in masonry cavity walls, through a small hole in the plasterboard between studs and noggings. As the foam sticks to the two sheets of plasterboard, it would make a very strong sandwich construction and give you insulation at the same time. Trouble is the cavity already has wool insulation...

The studs are closer near the wall ends, like doorways. The pitch of 600 mm is obviously there because it gives the pitch of 1200mm to fix the plasterboard leaves. There are extra noggings where the basin, bath and wall taps are located so that the stress is on the stud walls, not the plasterboard.

The thing is I am not worried about the plasterboard moving "a little", it is what I read in other postings about tiles coming off that worries me.

You have to be careful with expanding foam as it can expand and distort the plasterboard quite badly.

I think you would be very unlucky if the tiles fell off and once it is tiled I would guess that it would stiffen up the plasterboard considerably.

Shall I still use the flexible adhesive and grouting?

32KG Max per Metre. (Unplastered plasterboard)
20 KG if plastered

So weigh the tiles, calculate cements/grouts........and hey presto



Or Better still..........rip down plasterboard and replace with 12mm Hardibacker..........45kg per metre then

I already calculated the tiles weight and it is within the limit of what plasterboard can take. It is the support for the plasterboard that I was worrying about

Still would hardibacker it

The thing is I do not want to re-do a job that was done only recently. I am looking for a possible solution on what has been done already. I know there is always a better way to do it!

If the plasterboard is flexing...........then you need noggins...........not an easy thing to put in without removing plasterboard

The thing is I do not want to re-do a job that was done only recently

Might be a pain, but not as bad as replacing everything once the job is done and your not happy with it.