Door frame size and prebuilt rebated door casings

[macadonald]

Hi guys,

Hoping for some advice please. As part of my house renovations, I have removed the old door frames and casings and am replacing them with new frames on both solid walls and a couple of stud walls.

As my old ash block walls were all 2 inch, I've been using 2 inch (75mm) timber for the frames. I was advised to leave a gap of 2 inches bigger than the door I want to install. So for a 28inch door, my gap is 30inch and so on.

I plan on buy prebuilt door casings to fit in and pack till they are square. Firstly, is the 1 inch on either side enough? This would mean that the door casing at it's narrowest part would need to be no more than an inch.

Also, if I have 75mm timber, plus 2x 12.5mm plasterboard plus a little plaster, so is that works out to requiring a door casing that is approx 100mm wide.

Do all these dimensions sound okay to you? Am I okay carrying on like this. I know carpenters will make almost anything work, but I'm trying to save money and do it myself.

Thanks

 

[misterhelpful]

Standard door linings are approx. 27/28mm thick so I would suggest leaving a little more than 2" wider than the actual door to allow for packing both sides and thus minimizing any door trimming. I believe fire door linings are 32mm so you may need to take that into consideration.

Both are available in 4" (106mm) and 5" (132mm) widths so if you have 75mm studs (which are 3" not 2" as you stated) you will need the 4" ones as this will allow for the thickness of both plasterboards. If your studs are 2" then you may have to custom build your casings.

Door hanging is not the easiest job to get right if it's your first attempt, so good luck!

 

[macadonald]

Misterhelpful,

Thanks for your response. A little worried now. If the casing thickness is approx 27/28mm on each side, that certainly is a little more than 1" on either side. I assume your suggested 2" gap for packing etc is 2" on either side?

Will head out to Wickes and buy/measure up a casing tonight. Possibly something I should have done earlier.

I may get away with using 27" doors instead of the intended 28" doors I had originally intended. Anyone feel that 27" doors are too small for a bathroom and small 3rd box bedroom?

 

[misterhelpful]

macadonald,

The measurements I gave you were actually those of Wickes' door linings so it may be a good thing that's where you are planning to go!

The total thickness of both sides is approx. 56mm (2 and1/4") so you are not too far out if you have left 2", although 3" would have allowed plenty of room for any packing. If it is not possible to change the studwork, and assuming it is square, then the worst case scenario should be that you will have to trim your doors by about 1/2 inch. Other than that you could buy narrower, planed, stock timber, to make your own frames that will fit better.

It would have been wiser to get the casings first, as this would have given you a better idea of the opening required, but we all know hindsight is a wonderful thing.

With regards to the 27" door dilemma, many houses have this size for such rooms and hardly look any different. The only problem you may have is with large items of furniture.