Plasterboarding over cavity from old to new extension

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New Member

I wonder if anyone is able to give me some advice of what the best way is to plasterboard over the cavity onto existing interior wall?

I have had an extension done and have a doorway cut into the new extension. I wondered how I would go about going over the cavity, can I plasterboard straight over with no support in the cavity area as a door will not be used in this opening.
The exisiting plastered wall is there but I need it run flush but there is a door frame already there, and need to build the studwork to suit
Can hardwall be used here and the skim over the top if I fill in the hollow areas of the blocks with cement ?

I had attached some images so you can see what I am talking about, thank you for your time.


New Member
Hi Malc,

Thank you for your reply.
Where the plasterboard is against the blocks that is level with the existing wall, so I cannot put on top of the existing blocks, would Hard wall be okay to put in here, or would it crack?

Do you think it is worth filling up the hollow parts of the existing blocks with cement before the cavity closer in?

Thanks for your time


New Member
Hi Zolco

Thank you for your response, so just make all the brick and block work is level for dab and sits 15mm below the existing plasterwork so it ends up flush when plastered.