Door Frame Fitting: Plumb, Level and Wedging Technique

Summary

Fitting an internal door frame ("door lining" for internal doors; "door frame" usually denotes external) is one of the foundational carpentry tasks. The principle is simple — plumb, level, square, rigid — but the technique that delivers a frame the door will hang from cleanly for 25 years is more demanding than it looks.

The job sits at the boundary of first-fix and second-fix carpentry. First-fix carpentry typically installs the lining (the frame within the structural opening) before plaster; second-fix carpentry hangs the door, fits the architrave, locks and ironmongery after decoration. Many tradespeople, especially home-builders and small contractors, do both — but the techniques are different.

The single most common mistake is racking — the frame is plumb when measured but goes out of plumb when the door swings, because the frame is wedged in only one direction and twists under the door's weight. Wedge every fixing point in both directions; never assume "good enough" plumb at a single point.

Key Facts

• Door lining — internal frame, simple 3-sided assembly (no threshold), 22-32mm thick softwood standard.
• Door frame — external or robust internal frame, usually rebated, with a threshold.
• Standard internal door size (UK) — 1981mm × 762mm × 35mm (also written 78" × 30" × 1⅜"). Other common sizes: 1981×686, 1981×838, 2032×813.
• Fire door dimensions — FD30 typically 44mm thick, 1981×838 standard for accessible openings.
• Door clearance — 3mm gap on hinge, head and lock sides; 6-8mm gap at base above the floor (allows for carpet/finish).
• Lining width — must match the wall thickness. Standard widths: 88mm (4" stud), 113mm (4½" partition with plaster), 133mm (5"), 145mm, plus inch increments.
• Maximum fixing centres — 600mm per BS 8000-5; typically 4-6 fixings per side for a standard 78" door.
• Fixings — frame screws (8x100 or 8x125), or 100mm wood screws into hardwood/softwood plugs in masonry openings. Avoid brick-and-mortar nails — they split as the frame moves.
• Shim material — hardwood wedges or composite/plastic shims, never softwood (compresses over time).
• Plumb tolerance — better than 2mm over the full frame height (a 1.5m spirit level should show level along the full leg).
• Level tolerance — better than 1mm at the head over the door width.
• Door swing direction — convention: stand outside the room looking in, the door swings away from you; hinges are on the side you decide based on furniture layout and circulation.
• Architrave — the moulded trim around the frame after plaster, typically 70-95mm wide, mitred at corners at 45° (or with a square block in period properties).
• Door lining sets — pre-cut, pre-rebated 3-piece kits sold as "stop included" or "loose stop" sets. Most installers use stop-included.

Quick Reference Table — Standard UK Door Sizes

Detailed Guidance

Frame fitting sequence

DOOR LINING INSTALLATION — STEP BY STEP
=======================================
1. Check opening: width = door width + lining thickness × 2 + 6mm (3mm each side)
                  height = door height + lining thickness (top) + 12mm clearance to floor
2. Assemble lining: head + 2 legs, screwed (8x60 from outside, predrilled)
3. Cut legs to length (allow 6mm above floor — settled later)
4. Insert lining into opening, head at correct height
5. Plumb hinge-side leg first — front-to-back and side-to-side
6. Pack and fix hinge-side leg (top, middle, bottom — 3 fixings min for 78" door)
7. Square head — check diagonals (should match within 2mm)
8. Plumb lock-side leg — wedge until matches hinge-side
9. Fix lock-side leg
10. Check plumb again — adjust if needed
11. Test with door — hang temporarily before plastering

Plumb in both axes

This is where most installers fail. The frame must be plumb:

• Side-to-side (perpendicular to the wall) — the leg is vertical, neither leaning into nor away from the room.
• Front-to-back (along the wall) — the leg is vertical, not tilting toward the architrave or away.

Use a 1.5m spirit level on each face of each leg. A 600mm level shows local plumb but misses gradual twist. The full leg height must be plumb.

PLAN VIEW — TWO AXES OF PLUMB
=============================

       ROOM SIDE
           ▲
           │
    ──┬────┼────┬──
      │    │    │    ← Frame leg cross-section
      │    │    │      Must be plumb side-to-side
      │    │    │      AND front-to-back
    ──┴────┼────┴──
           │
           ▼
       PASSAGE SIDE

SECTION VIEW
============

  HEAD ──────────────
                 ▼ 
                 │  ← Frame leg
                 │     must be plumb
                 │     from base to head
                 │     (whole length)
                 │
  BASE ──────────────

Wedging technique

For each fixing point:

1. Drive a screw into the lining centre.
2. Behind the lining at that point, insert a pair of opposing hardwood wedges from each side of the frame.
3. Tap the wedges together (one from inside, one from outside) until the frame is tight against the structural opening on both faces.
4. Drive the screw home.
5. Check plumb — adjust wedges if needed.

Never leave a fixing point unwedged. Without a wedge, the frame is fixed at one face but can flex away from the other under door load.

For masonry openings, drill and plug at each fixing point with a 10mm plug, then 100mm woodscrew through the frame. Three fixings per leg minimum, six preferred.

For stud-wall openings, the structural opening is framed with a stud each side and a header above; the lining screws into these directly.

Fire doors — additional rules

FD30 and FD60 internal fire doors require:

• Intumescent strips in the lining rebate or door edge (manufacturer's instructions)
• Smoke seal as a separate brush/blade seal where required by BS 9999
• Maximum gap of 3mm around the door perimeter on hinge/head/lock sides; 8mm at threshold (sealed with intumescent if rated)
• Fire-rated fixings for hinges (intumescent pads behind each hinge)
• Self-closing device (overhead closer) on most regulated fire doors
• Door labels — every fire door must carry an identifiable manufacturer label confirming the fire rating

A fire door with a non-fire-rated lining is not fire-rated. Match the lining specification to the door specification.

Door hanging — second-fix

Once plaster is dry:

1. Mark hinge positions on door edge (top hinge 150mm from top, bottom hinge 230mm from bottom, middle hinge centred between).
2. Mark hinge positions on frame (matching).
3. Chisel hinge mortises (3-3.5mm depth for 75mm hinges).
4. Screw hinges to door (2 screws each, full screws after door hung).
5. Lift door into frame, screw top hinge first, then bottom.
6. Check swing — door should swing freely with consistent 3mm gap on hinge, head, lock.
7. Adjust shims under hinges if door binds or has uneven gaps.
8. Fit handle/latch — 1000mm from floor centreline standard.
9. Fit door stops if not rebated lining — set to allow door to close fully without slamming.

Common faults and fixes

Frequently Asked Questions

What's the difference between a door lining and a door frame?

A door lining is a simple 3-sided assembly (two legs + head) used inside the house, screwed into the structural opening. A door frame is usually rebated and may include a threshold; it's the more robust assembly used for external doors and sometimes for higher-spec internal fire doors. Most internal doors in modern UK housing are hung in door linings; the words are used interchangeably in practice.

How much clearance should I leave around the door?

Standard internal door: 3mm gap on hinge, head and lock sides; 6-8mm at the base above the floor finish. For carpeted areas, allow 10mm at the base. For fire doors, the gap is exactly 3mm — wider gaps fail the fire rating. The base gap on a fire door is filled with an intumescent threshold seal if required by the spec.

Can I use nails instead of screws to fix a lining?

No — modern best practice is screws only. Nails work loose as the building settles and the door is repeatedly used. Frame screws (8x100 or 8x125) are the standard. Hammer-fixed lining nails are sometimes seen in older properties but are not used in new work.

How thick should the lining be?

Standard internal lining is 22-25mm thick. For heavier doors (engineered hardwood, fire doors), use 32mm thick. The width (depth into the wall) must match the wall: 88mm for a standard 75mm stud + plaster, 113mm for a standard partition wall with plaster both sides, increasing in 1" increments thereafter.

What's the trick to hanging a door perfectly?

Hang the top hinge first with just one screw and check the door swings. Adjust if needed. Then add the bottom hinge with one screw, check again. Only when both hinges are correctly positioned should you add the middle hinge and the full complement of screws. This iterative approach catches misalignment immediately and avoids the "fix one hinge to find it's pulling the door out of plumb" trap.

Regulations & Standards

• BS 8000-5:2017 — Workmanship on building sites — Code of practice for carpentry, joinery and general fixings.

• BS 4787-1:1980 — Internal and external wood doorsets, door leaves and frames. Specification for dimensional requirements.

• BS 8214:2016 — Code of practice for fire door assemblies.

• BS 9999:2017 — Code of practice for fire safety in the design, management and use of buildings. Smoke seal requirements.

• Building Regulations Approved Document Part M — Access to and use of buildings. Door widths for accessibility (800mm clear width minimum for habitable rooms).

• Building Regulations Approved Document Part B — Fire safety. Fire door requirements.

• Building Regulations Approved Document Part E — Resistance to the passage of sound. Acoustic requirements for doors between flats.

• BS 8000-5:2017 (BSI) — primary workmanship standard

• Approved Document M — Access (gov.uk)

• Approved Document B — Fire safety (gov.uk)

• British Woodworking Federation — Door fitting guidance — industry body

• TRADA — Timber technical resources — timber industry standards

• skirting board installation — related second-fix work

• fire doors — fire door specification and rules

• architrave mitring — finishing the frame

• building regulations overview — Part M door widths