I intend to cut out some plasterboard to cover the fireplace in my lounge. I intend to keep the mantle but have the plasterboard cover the 930x930 tiled area including the actual fireplace.
A smoke bomb confirmed the chimnay can still be used in the future if required.
My question is can I just cover it up with plasterboard, skim it, then paint it or do I need to install a ventilator plate also?
If I need to install a ventilator plate why? and what is wrong with not installing a ventialtor plate?
I wouldn't use plasterboard for that application,i'd use MDF or plywood as it's stronger & doesn't need skimming. By installing a ventilator plate, you ensure air will drawn up the chimney flue reducing the risk of damp e.t.c.
It's the MDF dust that is bad for you - whilst you are cutting it. Do it outside and with a mask if you want belt and braces approach. The glue in the product is reputed to be the problem. A bit like asbestos cement sheets - not normally a problem unless one cuts it up.
If you don't ventillate the chimney you'll get damp build up there. This will combine with any soot deposits and become quite corrosive this in turn can over time attack brickwork in the chimney.
As Jake and Carrust mention, you could get a bit of damp - so if you do use MDF it might be adviseable to first seal it with a couple of coats of gloss paint on the inside. Damp and MDF don't mix!