Rough opening

A rough opening is the framed opening left in a wall to receive a door or window unit, sized to the unit plus a packing gap so it can be fitted square. The carpenter sets it out at frame stage, well before linings and second fix, and it is the structural hole the finished unit later sits in.

How it is set out and sized

• Build to the maker’s size. Window and door suppliers publish a rough-opening size for each unit. Frame to that, not to the unit’s own dimensions.
• Allow a packing gap. The opening is a touch larger than the unit (commonly around 10 mm each side) so it can be plumbed, levelled, and packed square, then fixed off. Too tight and it will not pack; too loose and there is nothing solid to fix to.
• Frame the opening properly. Jack and trimmer studs form the jambs; in a load-bearing wall a lintel carries the load over the head; a sill or threshold closes the bottom.

Why it matters

• Square and plumb. An out-of-square opening racks the unit, so a door binds or a window will not seal. Frame inspection checks openings before lining (see frame inspection).
• It is not the clear opening. The rough opening is the framed hole; the clear opening is the usable passage width once the door is hung and open, which matters for access and moving furniture.
• Wrong is dear to fix. Once linings, reveals, and trims are on, resizing an opening means pulling finishes off.

Also known as: framed opening, structural opening, RO.

Category: Carpentry / framing

Related

• First fix and second fix sequence
• Clear opening
• Lintel

See also

• Internal doors
• Timber windows
• Frame inspection checklist

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Last updated: 2026-05-26. Verified: 2026-05-26. Quarterly review for currency.