Can we tile and paint directly on to the plasterboard in our bathroom?

[CrapBag]

Bit of a cock up in our soon to be new bathroom. Plumber said to just tile over existing tiles to save time, money and taking them all off. We were going to but decided not to as they are about half the room and mainly unnecessary so we told him we wanted them off and my relative could do the plastering.

So he took them off yesterday, then came to ask me when the plastering was going to be done because that would delay things. Me being utterly clueless had no idea it would need be done first and it isn't possible. Relative is away then will be back at work. Plasterer that plumber knows has broken his hand.

I said he will have to carry on and just do what we can after.

When he was leaving for the day, he said he could put up plasterboard instead and we wouldn't need to get it plastered at all and we could paint straight on top. Is this right? I would be happy to do this but I don't want to end up with a shit looking bathroom. Problem is because the plastering can't be done, the walls will be bad behind the built in furniture which you will see when you open the cupboards so plasterboard would solve this.

Also the cupboard had to rebuilt and the shower is on the side of it (a plasterboard wall) The plumber also said it was OK to tile straight onto this but use unibond. Again, is this the right thing to do?

[PigletJohn]

In a bathroom, it is preferable to tile onto Tile Backerboard which is water resistant and will not crumble to mush when water gets to it.

The plasterer with the broken hand surely has a buddy or two.

[CrapBag]

Damn. Its already been put up. He said put a layer of unibond on first and it would be fine. I am assuming this is to make it water proof? What about painting directly on to it? Will it be OK with a couple of mist coats? Plumber said he has painted directly onto a plasterboard wall in his front room and it looks better than plaster as its perfectly smooth.

I don't know about the plasterer knowing anyone else, its someone the plumber knows, not us.

[PigletJohn]

you can put unibond on plaster if you are going to tile it, but not to paint over (it is water soluble, so emulsion softens it and may make it bubble or peel). Tilers sometimes use some kind of primer, Unibond is a PVA glue and not the best thing here.

If you are going to paint it, emulsion will be OK (use a vinyl silk which is more durable and washable than matt).

You can get Plasterboard Jointing compound which is a sort of fine filing plaster for the joints and nail heads. It is better than ordinary decorators filler. Wickes and builders merchants have it, you might find it at DIY sheds. Buy the smallest bag or tub. Apply sparingly and knife flat. Avoid sanding on plasterboard as you may damage the paper skin.