New interior door casing to knock through.

[AND1234]

What is the preferred method for door casings/frames where knock throughs are created into extensions?
The total wall thickness is 300mm.

Do you inset a standard casing leaving enough space for plasterboard and arc all the way around, or knock up full width casing (assuming its not hardwood and going to be white glossed...)

 

[noseall]

Return the plaster back to the casing.

Make sure that the casing width you choose allows you to overhang enough of the casing to deal with say 25mm of plaster material and still leave enough 'meat' for fixing to the masonry. So, a 133mm (5"-1/4) should do.

If you do decide to go down the full width route then you would need a decor plywood liner, as timber is likely to cup or twist.

 

[AND1234]

Return the plaster back to the casing.

Make sure that the casing width you choose allows you to overhang enough of the casing to deal with say 25mm of plaster material and still leave enough 'meat' for fixing to the masonry. So, a 133mm (5"-1/4) should do.

If you do decide to go down the full width route then you would need a decor plywood liner, as timber is likely to cup or twist.

Thats great cheers.
I think i'll go the 133mm casing route.
How much wider would you cut the opening then?
I guess i'd need the width of a casing (32"?) plus enough for plaster either side and the arc? So the casing would have to be packed off the brick a fair distance? Any one got any pics or drawings how this could be done?

 

[noseall]

This is the best way...

Make the opening about 2" wider than the overall casing width. A 30" door casing will be about 806mm overall so make your brick - brick 860mm.

Then buy a plasterboard and some drywall adhesive and line the entire opening, being careful to keep the minimum opening a few mill bigger than you need.

It is best to do, what will be the hinge side first and get it as true as yer boots then do t'uther side. I like to have say a 5mm fitting gap.

Once all the adhesive has gone off you are left with a nice level flat surface to fix your casing to. Be sure to mark off or take note of where all the full bricks are for fixing purposes. You will need 4" screws.

Always fix the hinge side of the casing tight against the plasterboard then pack the latch side.

Always damp the brickwork down before applying the dab.