Joining plasterboard corners without skimming

[jocollett]

Hello, hope someone can give me some advice.

I've moisture resistant plasterboarded our bathroom using large sheets and will be using tiles halfway up the walls to avoid obvious joints being visible. However there will be some visible internal corner joints and some external corner joints around the window.

I was wondering what the best way was to make these corners look ok. I'm wanting to paint directly onto the PB and avoid skimming.
Also do i need plasterboard primer before I paint?

Thanks

 

[Richard C]

Is it just the window reveals that's being left untiled?

 

[jocollett]

Hi Richard

My plan is to tile halfway up the wall and into reveals leaving the top half untiled and the bottom half tiled. This means there will be PB joints exposed where the reveal meets the wall and where the reveal meets the window.

Thanks

Jo

 

[Richard C]

I want to get an overall idea of the extent of untitled boards; what about the other walls in the bathroom, what's happening there?

 

[jocollett]

Ok. So looking left as you stand in the door. Wall 1 will be fully tilled with bath along it's length. Wall 2 (opposite the door) will hold the window and will be lower half tiled with the end of the bath in the left corner, then the toilet then the sink in the right corner. Wall 3 will be also be lower half tiled the top half is previously skimmed plasterboard that i'm keeping as is. There will be a radiator on this wall. The 4th wall holds the door on the right and the end of the bath with shower to the left. This will be tiled up to the roof behind the shower screen but above the door will not be.

Hope that makes sense.

 

[Richard C]

Yup, that makes sense. If the boards aren’t being plastered, it’s normal to use taper edge boards; the joints & internal corners are taped, filled & sanded flush.
External corner tape http://www.british-gypsum.com/produ...es/gyproc_accessories/gyproc_corner_tape.aspx
should be used on external corners &, again, filled & sanded flush. If it's going to have any chance of lasting, the whole must be sealed before decorating;
http://www.british-gypsum.com/produ...gyproc_accessories/gyproc_drywall_sealer.aspx

Leaving PB (even MR) unplastered in a damp environment such as a bathroom is a very bad idea. My advice would be to either fully tile the wall, including the reveals, or get the untilled section taped, skimmed & blended into the area to be tiled prior to tiling. It will cost a little more but will save all that messing about with tapes, filler & sandpaper & will look 1000 times better. Without reinforcing tape, any filler used on the internal corners will crack, the external corners will be very vulnerable & easily damaged & the face of the unplastered boards will be relatively soft, easily damaged & prone to effects of moisture. I’m no fan of tape & fill even if it's done properly but it’s never going to look good as a skim, especially if you’ve used square edge boards; but in a bathroom I think it would be a huge mistake.

Note that Moisture Resistant plasterboard must be primed before plastering;
http://www.british-gypsum.com/produ...le_plaster_bonding_agents/thistlebond-it.aspx

 

[jocollett]

Thanks Richard thats all really useful info. Sounds like I need to do some more work on it. I'll take your advice and either fully tile or skim the 2 exposed plasterboard sections.
Jo

 

[sweavo]

Hi Folks,

This thread's really helped me (thanks Richard). I have a similar goal, with the bath area tiled to the ceiling and all other areas mostly untiled.

I put up aquapanel (cement-based) around the bath area, and I gather that plaster doesn't bond properly to cementboard. The rest of the room is in tapered MR PB.

I'm thinking tile adhesive on top of the cementboard but skim on top of the MR plasterboard. I'm about ready to get the plasterer in but I'm faced with two questions.

1) best way to join MR PB to aquapanel

2) at the skim layer, how to make a neat transition from plaster to tile?

I had intended to paint onto PB but seeing it in place, skim would give a much better finish.

 

[Richard C]

I put up aquapanel (cement-based) around the bath area, and I gather that plaster doesn't bond properly to cementboard. The rest of the room is in tapered MR PB.

Knauf technical say not but that’s because they want you to buy their “special plaster”. It can be done using ordinary Gypsum if the surface is properly prepared & Knauf more or less admitted this to me. I had a special application in mind but it’s not usually an issue as AQP is normally a base for tiles; what were you proposing?

If skimming, you should use square edge boards rather than taper edge. It won’t be a problem, just a little more work for your spread; MR must be primed before plastering;
http://www.british-gypsum.com/produ...le_plaster_bonding_agents/thistlebond-it.aspx

I'm thinking tile adhesive on top of the cementboard but skim on top of the MR plasterboard. I'm about ready to get the plasterer in but I'm faced with two questions.
1) best way to join MR PB to aquapanel

Assuming your leaving the skimed PB untiled; I tape the joints as normal, prime the AQP as below & skim the PB over the joint & blend to nothing into & over the AQP. I always make the join at least 150mm outside the tiled/wet area. To prime the AQP for plaster, give it 3 coats of 1:1 PVA/water & leave it to dry out thoroughly for at least 24 hours; just before plastering, I mist spray the surface of the AQP with water & skim.

Some will advise to tank the AQP, this will make it bullet proof but it’s not really necessary in a domestic environment unless in a wet room; the choice is yours.

2) at the skim layer, how to make a neat transition from plaster to tile?

Plaster before tiling & get the plasterer to blend the skim to nothing around 300mm into the tile area; if he’s any experience with bathrooms, he should know what to do.

I had intended to paint onto PB but seeing it in place, skim would give a much better finish.

I think you’ve already gathered I don’t like tape & fill; to me it shouts cheap & nasty & I think you would be just asking for trouble in a bathroom.

 

[sweavo]

super helpful reply Richard, thanks a million.