Door opening in studwork

[Jupiter01]

Hi,

I know the exact size of door I am after and am trying to determine what size the opening in the studwork needs to be. Is there a simple formula I can apply? e.g. add x mm for door lining, etc.

I am planning to go with oak door lining so for the time being I just need to understand the size of opening in the studwall. This comprises of the timber upstand and the header to which I will eventually fix the door lining and then the door.

I hope this makes sense.

 

[noseall]

Typically a 30" door casing would sit inside a gap of aboot 32" wide along with a wee bit of packing.

We select uber straight studs for the door openings and fix the hinge side of the casing direct to one of the studs. The latch side we pack. If you are savvy, you can actually use the plasterboard edge to pack against though this is a wee bit risky, particularly if you don't get the boards bobbins.

However, some casing legs do vary in thickness. Our local BM stock a full 6" wide casing (for 100mm masonry walls that are to be dabbed) and these turn out a wee bit thicker than regular casings, so would require a slightly bigger opening.

We don't fit our stud header until the casing is in place. Always fix the header with a decent (15mm) gap above the casing header.

 

[Jupiter01]

Thanks @noseall.
Can I please clarify, does a "casing" refer to what I am calling the "door lining"?

Is it possible to determine the opening size (stud to stud) based on the target door size?

 

[noseall]

Can I please clarify, does a "casing" refer to what I am calling the "door lining"?

Yes they are similar. Both usually show a finished thickness of 20mm. A casing is a pre-cut moulding that has the rebate cut into it whereas a liner has knock-on strips forming the slammer strips.

Is it possible to determine the opening size (stud to stud) based on the target door size?

Yes as long as you know the finished size of your door lining. Either that or chance on larger fitting gaps.

762mm door + 40mm door liner (both legs) + 4mm fitting gap (both sides of door) + liner/casing packing? Add this lot up and it usually comes in at 32" in old money.

 

[Jupiter01]

When using solid oak door linings and not the stuff you can rub down, make good and paint white, is it best practice to put the door lining on after plastering?

 

[noseall]

You will need to seal the oak otherwise it will turn black when in contact with the acidic plaster.

 

[Jupiter01]

isn't it therefore best to put this on after plastering, I was wondering?