How to plaster over uneven boards?

[redhexagonal]

I had a wall that was not parallel to the wall opposite, so I built it out with plasterboard and moved the door frame a bit. How can I plaster over the stepped plasterboard, should I use undercoat/bonding first? It will be at least 12.5mm at the deepest bit (see pics 1 and 2) . There is also a bit on the right of the door that will need to be 5mm deep by the frame and 0mm by the wall (see pics 3 and 4) - what would be the best way to do that?

 

[foxhole]

Why did you step the plasterboard.?

 

[Alastairreid]

Put another bit of board in to make up the 12.5mm any other deviations can be made up with bonding after you have taped the joints.

 

[redhexagonal]

Why did you step the plasterboard.?

The wall was not parallel to the opposite side of the hallway, The door was about 20mm nearer to the opposite wall on one side than the other. So I moved the door frame out on one side , added 20mm of wood to the other side of the frame , dot and dabbed some plasterboard over the original board parallel on the left of the door but the rest of it I had to step some 9mm boards. Thats the flattest I could get it, basically the framing is not parallel and I’m trying to level the boards onto that frame. Its a new build and the framing is all over the shop

 

[redhexagonal]

Put another bit of board in to make up the 12.5mm any other deviations can be made up with bonding after you have taped the joints.

So I tape joints then try and get it roughly flat with undercoat plaster? Is it easy enough after that to get the wall flat with a skim coat?

 

[Alastairreid]

Any making up would be done with the bonding coat, you want a level surface for approx 3-4mm skim, the bonding can go to 10mm without slumping.

 

[lostinthelight]

Must have been bugging you a lot to go to that much trouble to true it, If you lived in an old stone property you'd be ecstatic if the walls were only that far out

 

[redhexagonal]

Must have been bugging you a lot to go to that much trouble to true it, If you lived in an old stone property you'd be ecstatic if the walls were only that far out

It was noticeable because it's a hallway. It tapered in about 40mm to the front door