Bonding over a skimmed wall

[dx90]

I have a studded wall in the bathroom at the end of the bath where the shower is going. It has been plaster boarded and skimmed over but I now find out that the old stud wall is not straight and is out of level.

Do I wet the skim down with water and then use bonding plaster to straighten the wall or do I PVA first and then bond and do I have to key the wall with a knife first?

I am a bit worried about the PVA not holding the weight of the bonding and tiles?

After tiling I understand I need to use the Aquaseal Wet Room Tanking System over the new plaster before tiling. Is this correct?

Thanks for any help and advice.

 

[joe-90]

Pull the PB off and use Aquapanel - true it up - and off you go.

 

[dx90]

Thanks for your advice but but I have no choice but to bond over the the skim at this piont. I have no transport and the delivery cost I can't aford. But I do have all the plaster I need to do the job.

Do you have any advice on bonding over the old skim please?

Thanks

 

[NickB_99]

Do you have any advice on bonding over the old skim please?

I think you are leaving yourself open to big problems here -
- when skimming over boards and tiling, the skim does not adhere strongly to the board and limits the weight of subsequent tiling - so generally tiling is done straight onto board.
- some tanking before tiling may probably protect the bonding underneath - but in general gypsum plaster does not like water-rich areas like in a shower and it usually finds a way. You have both gypsum multi-finish and bonding in the mix.
- PVA is water soluble so not great in a shower area
Joe is trying to steer you away from a mistake and a more robust solution in the long run. Maybe better to wait, save a bit and ask a friend to help with the boards. You're only talking about a shower area, which is not a huge area.
If you progress with bonding, lay out money for tiles, adhesives, get shower fitted etc you could find a big problem in the long run.

That said, if you're pressing ahead anyway, trying to plumb up a wall with bonding is do-able, but you'll need levels to work from.
Usually when floating Bonding you create a couple of screeds to work off. Usually make these with some thin pieces of wood and put plaster in between and float off these with a darby or straight edge. It depends how much thickness you need to build out. In could be a 'wedge' shape on the wall feathered to nothing, which I'd imagine is tricky - especially if you're not experienced.

 

[dx90]

Thank you for answering my questions and the advice. I will have a very good think about what you have both said before making a decision.

If I do go ahead and use bonding will I need to PVA the wall first or can I just wet it down and bond over., what is best?

Thanks

 

[Micilin]

Don't use PVA , use Thistle Bond it or Wickes Bonding Agent . Apply day one, plaster day 2

 

[dx90]

Micilin,

Why not use PVA and what is the difference between ThistleBond-it Plaster Bonding Agent and PVA?

Apart from the price.

Thanks

 

[dx90]

I've just been reading up on Thistle Bond-it Plaster Bonding Agent and some one said to just mix some sand into the PVA and brush that on the skim to give it a key as it does the same thing.

What do you think or does Thistle Bond-it dry into the wall differently?

 

[dx90]

I have a question about bond-it and similar products.

Does bond-it reactivate like PVA when it gets wet?

 

[Micilin]

I have a question about bond-it and similar products.

Does bond-it reactivate like PVA when it gets wet?

No, and PVA does not reactivate as much as start to break down!

 

[dx90]

Micilin, thanks for the answer.

 

[1john]

Bonding behind wiles on a wall at the head of a bath with a shower on is a recipe for disaster, aquapanel will be by far the cheapest and best option if you only need to do the job once.