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Bathroom Fitting

Plasterboard and Backerboard Next to Eachother on Breeze Block walls

Anonymous user 16/03/2024 - 2.45 PM

So, extension done and bathroom is going to be plastered soon (12.5mm board with dot and dab in all areas except shower. Tiler told me to use either construction board or tile backerboard (12mm). I have two questions; q1. On the part of the shower that is on the breeze block inner skin, how do I attach 12mm backerboard so it aligns with the dot and dab plasterboard that will be next to it?? I think I am reading I should dot and dab with tile adhesive and then screw through with plugs after its set? This way the plasterers will then be able to get them level with eachother. is this right? When you do come to mechanically attach, you are meant to drill through the dot and dab - how do you know where each dab is after its on? q2. When putting 12.5mmm plasterboard next to 12mm backerboard on studs, is it easy enough to tile level - I know its only 0.5mm. Im not tiling, but don't want too get it wrong for my tiler! Thanks for answering my silly questions!

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4 Answers

Dave Fettis

Rating: 5 out of 5

Canning Town, London

I would fix vertical batten at 300 centres. Ensure you are flush to the back of the dabbed p/board. The plaster board should be plumb both ways. No dips or bellies. You can cast a strait edge IE, your level, over your battens. You now know where to fix your CP/ backer board. You can pre mark and pre drill your backer board if desired you can use waterproof adhesive also. (Available in tubes) . Wd be nice if the CP board area was say 100mm bigger than the wet area. Even a 1 mm step is not too much for the tiler to overcome. He should us a 5 mm notched trowel with a quality powder mix flexible adhesive. ( Not the rubbish in a tub ) ensure he uses PVA ON THE FRESH BOARD.

Answered1 December 2021

Anonymous user

I would mount the backer board using treated batons cut down to size as spacers you could use the addition of dot and dab as extra security but once the backer board is fixed in place with screws it is not going to move anyway. A .5 mm discrepancy is not Going to make a great difference to the Plasterer. Equally the Tiler will be very used to using a suitable adhesive off which they can build up a surface should they need to.

Answered2 December 2021

Chris Morgan Bathrooms

Rating: 5 out of 5

Bridgend, Mid Glamorgan

Agree with the previous answer until the end, Do Not use PVA on any tile surface substrate, adhesive companies will not warranty if it fails. PVA is a plasterer’s compound, it forms an impervious layer so laid on plaster dries at the same rate, if used under tile adhesive it will rehydrate, become creamy then partially Crystalize , making a powdery surface between your wall and tile adhesive, is not definitely going to fail be could well do. Use SBR recommended for tiling.

Answered6 December 2021

Wigglesworth Limited

Rating: 5 out of 5

Southampton

Alternatively, use a build up of battens in the wall, then 9mm ply finished with 9mm plasterboard which you then waterproof with a tanking system. This gives you some insulation, the knowledge that you can fix pretty much anything anywhere, a flexible backing which will not fail via the plasterboard, all completely waterproof. Not a cheap option, but no comebacks.

Answered7 December 2021