Door size and opening size are not the same
In quotations and bills of quantities doors are described by their door size (e.g. 900 × 2100), while the opening in the wall must be slightly larger to take the frame and leave room for fitting. How much larger depends on the frame type – which is why every quotation of ours includes opening preparation guidelines for the doors offered.
Example: for one common frame type the structural opening is door width + 20 mm and door height + 10 mm, with a tolerance of about ±5 mm. Other types have other dimensions – always check the guidelines for the specific door.
The opening height is measured from the finished floor. If the floor is not laid yet, agree the finished floor level with the flooring contractor – otherwise the door will not fit after the floor is laid, or the gap under the leaf will be too large.
Wall type and thickness
The manufacturer's instructions specify which walls the door may be fitted in – masonry, concrete or plasterboard – and how thick they must be. With some frames the wall must be at least 10 cm thick, and in plasterboard walls the opening must be reinforced with studs as instructed.
The wall around the door must have at least the same fire rating as the door – an EI2 60 door in a wall that lasts 30 minutes does not give 60 minutes of protection.
Rebated frame or tubular frame
There are two common ways of fitting:
- a frame that rests against a rebate in the wall – the opening needs straight, plumb reveals and enough room for the frame overlap (e.g. at least 30 mm)
- a tubular (wrap-around) frame – it wraps the wall, so any wall thickness works; practical for replacing existing doors
Which type suits depends on the opening – so please send a photo of the opening with the sizes.
Before the doors arrive, check
- the opening width at three heights (bottom, middle, top) and the height on both sides
- that the reveals are plumb and the wall around the opening is flat
- the finished floor level and whether there will be a threshold
- that there is solid material around the opening for fixing – no voids or crumbling plaster
- that finishes (plaster, linings) are done or planned as instructed
What not to do
Do not force a door into a narrow opening by cutting the frame, do not shorten the leaf because the floor is too high, and do not fill an oversized gap with expanding foam unless it was tested with the door. Any such “adjustment” can void the door's classification – more in the article on installation as part of the system.
Measuring on site
If you are not sure, by arrangement we come to site and measure the openings and check the handing before ordering – site visits are charged by distance. For a quotation, sizes and photos of the openings are enough; see the fire doors page for what else we need.
