Door linings and door frames are two different things, and confusing them at the timber merchant leads to ordering the wrong product and rework on site. This guide explains the distinction, covers common sizes and materials, walks through installation, and gives 2026 UK pricing so you can budget accurately from the start.
Door Lining vs. Door Frame: What’s the Difference?
A door lining (also called a door casing in some regions) is a simple three-piece surround that lines the opening in a timber-frame or masonry wall. It consists of:
- Two vertical side jambs (legs)
- One horizontal head jamb (top)
The lining sits inside the structural opening, fixed to the surrounding studwork or masonry with screws and packers. The door is then hung directly from the lining — hinges are cut into the lining’s face or rebate.
A door frame (or door set) is a more robust, factory-machined unit, typically used for external doors or fire doors. It includes a substantial rebated section that the door closes against and is engineered to support greater weights, provide weatherseal, and offer fire resistance. Frames are usually supplied with a sill for external applications.
In practice: interior domestic doors in the UK almost always use linings. External doors and fire-rated doors use frames. A carpenter quoting for “hanging internal doors” will almost always assume linings unless specified otherwise.
Standard Sizes
UK door openings follow standard rough opening (RO) dimensions, and linings are specified to suit.
Lining Width
The critical dimension: the lining must span the full wall thickness so the face of the lining leg sits flush with the plasterboard or plaster surface on each side. Standard wall thicknesses and corresponding lining widths:
| Wall Construction | Approx. Wall Thickness | Standard Lining Width |
|---|---|---|
| 100 mm stud + 12.5 mm PB each side | 125 mm | 133 mm (allows for packing) |
| 100 mm stud + 15 mm PB + skim | 132 mm | 138 mm |
| 140 mm stud + 12.5 mm PB each side | 165 mm | 170 mm |
| 215 mm brick + 12.5 mm plaster each side | 240 mm | 245 mm |
Most timber merchants stock linings in widths from 95 mm to 245 mm in 5 mm increments, or sell wider boards for cutting down on site.
Lining Height and Length
- Head jamb: typically 838 mm or 926 mm for standard single doors (838 mm for a 762-wide door, 926 mm for an 838-wide door)
- Side jambs: 2100 mm minimum; commonly sold at 2100 mm or as 4.8 m lengths
Standard UK door sizes follow BS 4787:
- 762 × 1981 mm (2’6” × 6’6”) — the most common interior door
- 838 × 1981 mm (2’9” × 6’6”)
- 686 × 1981 mm (2’3” × 6’6”) — narrower, used in en-suites and WCs
Lining Materials
Softwood (Redwood / Whitewood)
Scots pine or similar Scandinavian softwood. The default material for painted interior door linings. Usually supplied with a slight moisture content tolerance — allow to acclimatise for 48 hours in the building before fitting.
- Grain can telegraph through paint if not primed correctly
- Easy to cut and fix; works with standard hand tools
- Available primed or unprimed; primed is worth the small premium
MDF (Medium Density Fibreboard)
Increasingly popular for painted applications. Absolutely stable — no grain, no movement — giving a flawlessly smooth paint finish. Heavier than softwood, which matters when handling 2.1 m lengths. Does not tolerate moisture; not suitable for bathrooms or external-adjacent openings. Also less robust for hinge fixing: pilot holes are essential to prevent splitting.
Hardwood
Oak, ash, or sapele for clear-finished (varnished/oiled) linings. Significantly more expensive. Often used in heritage properties or high-specification joinery.
Engineered / Veneered
A substrate (typically LVL or MDF) faced with a hardwood veneer. Good stability, lower cost than solid hardwood, used in mid-range joinery.
Lining Types
Plain lining (no rebate): the simplest form. Architrave covers the joint between lining and wall surface. The door stop — a small planted bead the door closes against — is nailed to the lining face after hanging.
Rebated lining: factory-machined with a 12 mm deep rebate for the door to close into. More common in fire-door applications where the rebate is part of the fire seal. Slightly more expensive but a neater finish and better acoustic seal.
Pre-machined / pre-hinged lining sets: the lining is machined with hinge recesses and strike plate positions already cut to match a specific door size. Labour-saving on site; worth the premium when hanging multiple identical doors.
Costs (2026 UK Trade Prices)
| Item | Specification | Approximate Cost |
|---|---|---|
| Softwood lining set (unprimed) | 133 mm wide, standard door | £20–£35 |
| Softwood lining set (primed) | 133 mm wide | £28–£50 |
| MDF lining set | 133 mm wide | £25–£45 |
| Hardwood (oak) lining set | 133 mm wide | £70–£140 |
| Pre-machined softwood lining set | 133 mm wide, hinge recesses cut | £40–£90 |
| Softwood door stop bead | 2.1 m length | £2–£5 |
| Carpenter to fit lining | Per door | £60–£120 (plus materials) |
Installation Overview
- Check the rough opening: width should be door width + 20 mm for linings + 10 mm packing clearance each side; height should be door height + 15 mm head clearance.
- Mark the centre line of the opening and work outward symmetrically.
- Fix the head jamb first using frame fixings (75–100 mm) through the lining and packers into the lintel or head stud. Check level.
- Fix the side jambs: plumb using a spirit level; screw through the jamb at hinge, lock, and mid-point positions into the studwork or masonry packers.
- Check the diagonal from corner to corner — both diagonals equal confirms the opening is square.
- Hang the door: mark and cut hinge recesses, fit hinges, offer the door up, pack as needed.
- Fix the door stop: once door is hung and closes freely, nail the stop bead in place with the door in the closed position to guarantee a consistent gap.
- Fix architrave: cover the joint between lining and wall surface on both sides. Mitre the corners at 45°. Align the architrave face 3–5 mm back from the lining face (the “reveal”).
Building Regulations
For fire doors (required in all new dwellings at the door to an integral garage, between floors in houses of 3+ storeys, and in conversions to flats), the frame and lining must be compatible with the door’s fire rating (typically FD30 or FD60). Frame rebates must be at least 25 mm deep. Intumescent strips and smoke seals are required — many are supplied pre-fitted to the door edge or must be fitted into the frame rebate. Check Part B of the Building Regulations and the door manufacturer’s installation instructions.
For acoustic performance in new-build party walls (Part E), linings must be installed to minimise sound flanking paths — solid packing and acoustic mastic around the perimeter.
Getting the lining specification right before ordering saves the frustrating scenario of a carpenter on site planing down a lining that’s 20 mm too wide, or worse, returning to the merchants mid-job.
