replacing an interior door frame

[samohtom]

Hi. I've ripped out one of my interior doors and all the wooden frame around it, and now need to replace. My rough opening is 206.5cm x 77cm. There's the potential to make this about a cm bigger vertically and maybe 2cm horizontally, because there's about a cm of plaster (with mesh in it) all around both sides of the opening. The old frame was rebated both sides with the rebates facing the breezeblock wall (hope this makes sense). I was wondering what the best size frame to buy would be? Old frame is about 131 x 32mm thick. Wickes do this http://www.wickes.co.uk/Rebated-Softwood-Door-Casing/invt/200332 but it's for a 762mm door. Now forgive my ignorance, but my impression is that the Wickes door Casings go directly next to the masonry and as their linings have no rebate it makes sense that they would go inside the door casing and the door then inside the door lining?! My old door just fitted to the wood that was attached to the masonry directly.

Also, frame fixings which I can get from Screwfix etc - how do they work? With a rawl plug you have to drill, fit plug, place what you want to secure then screw in. I'm sure I've read somewhere that you just drill straight through the frame for fixing though?!

 

[r896neo]

Normal door lining sets have no rebates on the back yours was probably done like this in order to fit the lining into an opening which was built marginally too small. The door lining/casing attaches to the wall and the door hangs on this, the architrave and door stops are also attached to the casing.

You can fix it with whatever you want. Concrete screws need no plug and are better than frame fixings in my opinion. Fix the hinge side level and plumb then hang the door then true up the other side and fix it.