Deep internal door lining

[stephen_lowfield]

Hi,
I am doing a self build extension and struggling how to do this:
I need a door liner for the bathroom door. its a old external wall the thickness will need to be 340mm (this is including the 12.5mm plasterboard either side as I have done battens on either wall)
My thoughts is to use plywood (possibly 9mm) and then attach the door liner through the plywood into the brickwork behind. Is this the right way to go about it or is there another way?

 

[JohnD]

I have lived in an old house with thick walls.

You can fix battens to the brickwork around the front and back of the opening, and an extra one where you will hang the door to take the screws, then fix a skin of ply. Use mouldings to hide the joints and give a nice architrave.

In upmarket houses, the lining is panelled to match the door.

I would pack the cavity behind the skin with mineral wool and seal with pink fire foam. This will prevent draughts and muffle noise, and in the unlikely event of a fire will block smoke and flame in the void.

If the building requires fire doors, you would have to detail it to comply with regulations, which I do not know as they change often.

 

[chirpychippy]

I would, assemble the door lining brace the bottom of the lining with a batten and possibly the middle to hold the frame parallel, brace the top corner either using a square or the 3,4,5 method. Offer the lining into the hole, plumb it level it as best you can, then you can work out what size the packing needs to be left and right.

I would suggest 4 screws each side, pack behind the hinges. Get everything bang on level and plumb, foam the rest.