Door Frame Installation: Lining Sets, Packing & Plumb/Level Checks

Summary

Door frames and linings are among the most important second-fix carpentry items. A door that sticks, binds, swings open on its own, or won't latch properly almost always traces back to a lining that was not set accurately. Getting the lining right before the door is hung eliminates 90% of door problems — and rehinging a door on a bad lining is a frustrating, time-consuming exercise.

The terminology varies by trade. A lining (or lining set) is the timber surround inside a partition or studwork wall opening — it has no external rebate and accepts a separate stop bead. A frame (or door frame) has an integral rebate moulded in and is typically used for external doors or internal fire doors where a solid rebated frame is required for gasket or intumescent strip installation. Most internal domestic doors go into linings; external and fire doors go into frames.

The door width and height determine the opening size but the lining sets the finished aperture. Understanding the relationship between rough opening, lining size, and finished door size is fundamental. Getting the rough opening wrong means re-trimming the opening — far more work than getting it right first time.

Key Facts

• Standard door sizes (UK): 1981×610mm, 1981×686mm, 1981×762mm, 1981×838mm, 2040×826mm (newer standard)
• Rough opening width: Door width + 2 × lining thickness + 2 × packing allowance (typically 10mm each side) + clearance (5–6mm each side for door) — total = door width + approx. 50mm for internal
• Rough opening height: Door height + head lining thickness + packing + floor clearance (typically 5–10mm gap to floor covering) — total = door height + approx. 60mm
• Standard lining thickness: 32mm or 38mm PAR softwood
• Standard lining width: 95mm (for 75mm stud + 2 × 12.5mm board = 100mm wall), 108mm, 133mm, or custom to match wall thickness
• Width tolerance: Lining should match wall thickness exactly — overwide linings require scribing; underwide linings leave a gap requiring cover strips
• Fix per leg: Minimum 3 fixings per leg on a 2.0m door height; fix at top, bottom, and middle minimum
• Screw size: 100mm × 5mm screws into stud, or 75mm × 4mm into header over opening
• Packing material: Hardwood or plywood packing pieces, or proprietary polypropylene packing wedges; never use compressible material
• Stop bead width: Typically 12mm × 38mm planted stop; position 3mm back from the face of the door for a shadow gap effect, or tight against the door face for sound reduction
• Fire door lining: Must be solid hardwood or engineered hardwood, not softwood — check fire door supplier specification
• Intumescent strip: Fitted in a groove in the rebate or stop of a fire door frame; check FD30 or FD60 specification for size
• Hinge positions: Standard residential: 150mm from top and bottom of door; third hinge at mid-point for doors over 2040mm or heavy/fire doors
• Door clearance gaps: 2mm at hanging side and closing side; 3mm at top; 5–8mm at bottom (to floor covering, or 10mm over carpet)

Quick Reference Table

Detailed Guidance

Sizing the Rough Opening

Before framing the rough opening in a stud wall, calculate the correct size.

Width calculation:

• Chosen door: 762mm
• Lining two legs (both sides): 2 × 32mm = 64mm
• Packing both sides: 2 × 10mm = 20mm
• Door clearance both sides (fitted gap): 2 × 3mm = 6mm
• Rough opening width = 762 + 64 + 20 + 6 = 852mm (approx. 855mm as built)

Height calculation:

• Door height: 1981mm
• Head lining: 32mm
• Packing at head: 10mm
• Door top clearance: 3mm
• Floor to finished floor covering: 8mm (carpet) or 5mm (hard floor)
• Rough opening height = 1981 + 32 + 10 + 3 + 8 = 2034mm minimum

Frame the opening using king studs and trimmer studs (see stud walls). Always fit a header over the opening — a doubled 47×100mm minimum for stud wall openings.

Fitting the Lining Set

Step 1 — Prepare the opening:

• Check rough opening is close to calculated size
• Plumb the trimmer studs using a long spirit level — out-of-plumb studs make the lining hard to set correctly

Step 2 — Assemble the lining:

• Most lining sets arrive in three pieces to be assembled on site
• Join head to legs using lining cramps, pocket screws, or pinned housing joints
• Check the assembled lining is square: measure diagonals — they should be equal within 1mm

Step 3 — Set and fix:

• Offer the lining into the opening
• Use folding wedges (pairs of tapered packing pieces driven from each side) to hold the lining in position
• Level the head using a spirit level — adjust packing under each leg
• Plumb each leg in two planes (face and edge) using a spirit level
• Check squareness again by measuring diagonals — adjust packing as needed
• Fix through the lining into the stud/trimmer with 100mm screws at packing positions only — do not over-fix as this can pull the lining out of true
• Recheck plumb and level after each fixing is made

Step 4 — Finish:

• Once fixed, check that the lining face is flush with the plaster face on both sides (or set for the planned plaster depth if plastering after lining installation)
• Fit the architrave (see skirting architrave)

Hanging the Door

With the lining set plumb and square:

1. Plane the door to fit the opening with correct clearances (2mm each side, 3mm top, 5–10mm bottom)
2. Mark hinge positions on the door — standard positions are 150mm from the top and 225mm from the bottom (to centre of hinge knuckle)
3. Mark corresponding positions on the hinge leg of the lining — ensure the door marks and lining marks are at the same height
4. Cut hinge recesses to the exact hinge leaf thickness — recesses must be exactly right. Too deep, and the door binds on the hinge side; too shallow, and the door binds on the latch side
5. Fix hinges to door first, then offer up and fix to lining
6. Check operation — door should swing freely and remain stationary when released at any angle (not swing open or close on its own, which indicates the lining is out of plumb)
7. Mark and fit the lock/latch and strike plate last

Fire Door Linings and Frames

Fire doors (FD30, FD60) must be hung in a solid frame with intumescent seals. Requirements:

• Frame material: Solid hardwood or equivalent — must achieve fire resistance to match the door
• Intumescent strips: 10mm × 4mm or as specified by the door manufacturer — route into the frame rebate or stop bead
• Cold smoke seals: Fitted to the top and latch edge on FD30 doors in sleeping risk locations
• Hinges: Minimum 3 ball-bearing hinges for FD30; fire-rated steel hinges (CE marked) — check door manufacturer's specification
• Certification: Fire doors must be supplied with a certificate of conformity; the completed door, frame, and hardware combination must match a tested specification
• Door closers: Required on all fire doors — check the closer is rated for the door weight and achieves full latch engagement

External Door Frames

External door frames differ from internal linings:

• Rebated frame: The rebate stops draughts and provides a weathertight seal location
• Weatherbar: Aluminium or hardwood weatherbar threshold — must direct water away from the interior
• DPC: A damp-proof course must be installed behind the frame at the threshold and at the jambs before fixing to masonry
• Frame fixing: Expanding bolts into masonry at 600mm centres, or frame fixings through the frame into the reveal
• Insulation and draught seal: Fill the gap between frame and masonry with low-expansion PU foam; fit draught-stripping around all edges

Frequently Asked Questions

What causes a door to swing open or closed on its own?

The lining is out of plumb. If the hinge leg of the lining leans backward (top away from the room), the door will swing open. If it leans forward (top into the room), the door will swing closed. Check the hinge leg with a long spirit level. Another cause is hinges that are recessed to different depths — unequal recesses tilt the door face relative to the lining.

My door keeps dropping and binding at the bottom — what has gone wrong?

The screws in the top hinge have pulled out. This is usually a fixings problem — screws into thin door stiles or into the lining timber at the wrong depth. Refit with longer screws (50mm into door stile, 50mm into lining). On a heavy door, fit a third hinge.

Should I fit the lining before or after plastering?

Either approach works, with different requirements. Fitting before plastering means the lining acts as a screed guide and the plaster is brought up to the lining face — neater result but the lining must be protected during plastering. Fitting after plastering allows the plaster to dry completely and gives a clean reference surface — the lining face is set flush with or just proud of the plaster. Both methods are used in practice.

What size lining do I need for a 100mm stud wall with 12.5mm plasterboard?

A 100mm stud wall with one layer of 12.5mm plasterboard each side gives a total wall thickness of 125mm. A standard 120mm lining is a near match but will sit 5mm proud of the plaster face on each side — these can be left as a shadow reveal or covered with a narrow scribing strip. A custom 125mm lining is the ideal fit. Check with your supplier for the nearest available width.

Can a fire door be fitted in a standard softwood lining?

No — fire doors must be fitted in frames that form part of an approved tested combination (door + frame + hardware). Most FD30 fire door manufacturers specify solid hardwood or engineered timber frames. Using a standard softwood lining with a fire door invalidates the fire rating and would fail a Building Control inspection.

Regulations & Standards

• Building Regulations Approved Document B (Fire safety) — fire door requirements, means of escape

• Building Regulations Approved Document M (Accessibility) — door opening widths for accessible dwellings

• BS 8214 (Timber-based fire door assemblies — code of practice for installation) — fire door installation requirements

• BS EN 1154 (Building hardware — controlled door closing devices) — fire door closer standards

• FDIS — Fire Door Inspection Scheme — Fire door specification and compliance guidance

• Timber Research and Development Association (TRADA) — Door frame and lining specification

• Building Regulations Approved Document B — GOV.UK — Fire door requirements

• skirting architrave — Architrave fitting after lining installation

• stud walls — Framing openings in stud walls

• part b fire — Fire door requirements and compartmentation

• part m access — Accessible door widths