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Internal doors

838mm internal doors (78" x 33")

838mm is the widest standard imperial internal door, quoted as 78" x 33". It is specified for wide openings, main reception rooms, and routes that need more clear width than a 762mm door can give. A wider leaf is also a heavier one, which changes the hinges and the frame fixings.

Most people arriving at 838mm are here for one of two reasons: an opening that is genuinely wider than standard, or an accessibility requirement that a 762mm door will not satisfy.

They are different problems, and only one of them is solved by the door on its own.

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Accessibility and clear opening width

The measurement that governs whether someone can get through a doorway is the clear opening width: the usable gap with the door standing open. It is always less than the leaf width, because the frame, the stop and the thickness of the open leaf all take a share.

Approved Document M sets clear opening widths for dwellings, and the required figure depends on the width of the approach — a doorway off a narrow corridor needs a wider clear opening than the same doorway off a generous hall. [VERIFY: Approved Document M, current edition] and confirm the figure against your own layout before ordering.

Where clear width is critical, the frame and the hinges do as much work as the leaf. Rising butt hinges or wide-throw hinges let the door swing fully clear of the opening, which recovers width that a standard hinge gives away.

A wider door is a heavier door

Leaf weight scales with area, so an 838mm door is meaningfully heavier than the 762mm version of the same product. On a solid core or a solid oak leaf that weight starts to test a two-hinge hanging.

Fit three hinges rather than two on the wider sizes, and check what the existing frame is fixed to before you hang anything heavy on it. A lining that was pinned to a stud partition and has carried a hollow core door for 30 years is not automatically ready for a solid oak one.

If 838mm is still not wide enough

Beyond 838mm the imperial range stops, and the usual answer is a pair of doors rather than one very wide leaf. A pair of 610mm or 686mm doors on a wide opening gives you the width without a leaf so heavy it drops on its hinges, and it lets you open one side day to day and both when you need them.

Sliding and pocket doors are the other route where swing space is the constraint rather than width.