Hanging an exterior door is a physically demanding but straightforward carpentry task if approached methodically. The common failure modes are doors that bind in the frame, gaps that let in draughts, and poorly aligned strikes that either do not latch properly or require slamming. All of these are avoidable with accurate measurement, careful hinge positioning, and patient adjustment. This guide also covers the Building Regulations requirements that apply when you replace an exterior door — obligations that catch many homeowners by surprise.
Tools Needed
- Tape measure and combination square
- Pencil and marking gauge
- Hand plane (jack plane for straightening, block plane for final fitting) or power plane
- Chisel set (25 mm for hinge morticing)
- Mallet
- Drill/driver with drill bits and driver bits
- Hinge template (jig) — strongly recommended
- Packers and shims (hardwood or composite)
- Spirit level (1.2 m)
- Screwdrivers
- Handsaw or jigsaw (for trimming door bottom)
- Weatherstripping and threshold bar
- Silicone sealant and gun
Understanding UK Exterior Door Sizes
UK door sizes are standardised but the range is relatively limited. The most common exterior door heights are:
| Width | Height | Common Context |
|---|---|---|
| 762 mm (2’6”) | 1981 mm (6’6”) | Standard pre-1970s housing |
| 813 mm (2’8”) | 2032 mm (6’8”) | Some older properties, garages |
| 838 mm (2’9”) | 1981 mm (6’6”) | Standard modern housing (most common) |
| 914 mm (3’0”) | 1981 mm (6’6”) | Wider access, some period properties |
Always measure the existing opening (the clear structural opening in the masonry or timber frame) before ordering a door. A 1981×838 mm door leaf requires a frame rebate of approximately 1994×851 mm and a structural opening of approximately 2040×910 mm — allowing for the frame, packers and plaster returns. If replacing like-for-like in an existing frame, measure the old door leaf directly.
Measure height and width in at least three places: top, middle and bottom (for width) and left, centre and right (for height). Frames are rarely perfectly parallel, and the narrowest measurement governs.
Door Material Comparison
| Material | Cost Range (supply only) | U-Value | Maintenance | Lifespan |
|---|---|---|---|---|
| uPVC | £300–£700 | 1.2–1.6 W/m²K | Very low | 20–30 years |
| Composite (GRP skin, foam core) | £700–£1,800 | 0.9–1.4 W/m²K | Low | 30–35 years |
| Timber hardwood (oak, meranti) | £600–£2,000 | 1.4–2.0 W/m²K (solid); 1.0–1.4 W/m²K (engineered) | Medium–high | 30–50+ years with maintenance |
| Aluminium | £1,000–£3,000 | 1.0–1.4 W/m²K (thermally broken) | Low | 30–40 years |
Composite doors dominate new installations in the UK due to their low maintenance, good thermal performance and wide range of styles. Timber doors remain popular in conservation areas and period properties, and many local planning authorities require like-for-like replacement to preserve character. Always check with your local authority before changing door material in a conservation area.
Building Regulations: What You Must Know
Part L — Thermal Performance
Approved Document L1B (Conservation of Fuel and Power in Existing Dwellings) requires that replacement windows and doors in existing dwellings achieve minimum thermal performance. As of the 2021 edition (effective 2022), the requirement for a replacement door is:
- Centre-pane U-value ≤1.4 W/m²K for replacement external doors where more than 50% of the door’s internal face area is glazed
- Whole-door U-value ≤1.4 W/m²K for a solid or predominantly solid door
Most compliant composite and uPVC doors from mainstream UK suppliers already meet this threshold and will provide a FENSA or CERTASS certificate on installation if fitted by a registered installer. If you fit the door yourself, you must notify the local authority building control department and they will inspect it. Alternatively, have the door supplied and fitted by a Competent Person scheme member who can self-certify.
Timber solid doors, particularly older ledged-and-braced designs, often do not achieve 1.4 W/m²K without a thermal core or heavy weatherstripping. If replacing a non-compliant door in a listed building, a relaxation may be negotiable with building control.
Document Q — Security
Approved Document Q (Security, 2015) applies to new dwellings (new builds and change of use, not straightforward like-for-like replacements in existing homes). It requires that entrance doors meet PAS 24:2022 — a rigorous physical and manipulation attack test including anti-crowbar, anti-drill and lock manipulation resistance.
If your project is a new build, a barn conversion, or a change of use that requires a full building regulations application, the entrance door must carry a PAS 24:2022 certification. Many composite door manufacturers supply doors pre-certified to PAS 24:2022 — look for this on the product specification, not just in the marketing copy.
For ordinary like-for-like replacements in existing homes, Document Q does not apply, but fitting a BS 3621-certified lock and Secured by Design hardware is still best practice and may be required by your home insurer.
Step-by-Step: Hanging an Exterior Door
Step 1 — Prepare the frame. Check the existing frame is square, plumb and in sound condition. Rot in the frame must be cut out and repaired before hanging a new door. Use a spirit level to check all four sides. Note any out-of-plumb or out-of-square — you will plane the door to match the frame rather than assume the frame is true.
Step 2 — Size the door leaf. A correctly fitting door should have a gap (known as the ‘stile clearance’ or ‘hanging gap’) of approximately 2–3 mm on the hinge side, 2–3 mm on the latch side, and 2 mm at the head. The threshold gap depends on the floor finish and any threshold bar fitted — typically 5–10 mm. Transfer the frame measurements to the door and mark the lines to be planed or sawn.
Step 3 — Plane to size. If trimming more than 5 mm from the width, use a circular saw or jigsaw first, then finish with a plane. Always plane from the face to the back to avoid splitting the face veneer. For the top and bottom, plane inwards from each corner to avoid breaking out the face.
Step 4 — Mark hinge positions. For exterior doors, use three 100 mm (4-inch) hinges — two are inadequate for the weight and wind-loading of an exterior door. Standard hinge positions are 150 mm from the top of the door, 250 mm from the bottom, and one centred between them. A hinge jig ensures consistent positioning between door and frame; it is the most reliable way to avoid misaligned hinges.
Step 5 — Mortice the hinges. Use the hinge as a template, scoring around it with a Stanley knife. Chop out the mortice with a chisel to the depth of the hinge leaf — no more. A hinge leaf recessed too deeply causes the door to bind; one not recessed enough leaves a gap at the frame. The hinge should sit exactly flush with the surface.
Step 6 — Fit hinges to the door. Fix the hinge leaves to the door with the screws supplied. For timber doors, pilot holes prevent splitting. Use all screws — short-hinging a heavy door by using only two screws per hinge is a common cause of hinge failure.
Step 7 — Hang the door. With a helper or door horses, lift the door into the frame and pack it at the correct height with shims under the bottom edge. Align the door hinges with the frame mortices and fix the frame side of the hinges. Open and close the door — check the gaps on all sides and that the door swings freely without binding.
Step 8 — Adjust and plane as needed. Doors rarely fit perfectly on first hanging. Tight spots will leave witness marks on the frame — plane those areas carefully. If the latch side does not close flush, the hinges may be over-morticed (causing the door to spring away from the latch side); pack out the hinge mortice with thin card.
Step 9 — Fit the lock. Mark the lock body position on the door edge and chisel out the mortice to accept the lock case. Mark the spindle, keyhole and bolt positions on the face and drill through. Fit the latch/lock body and mark the frame for the strike plate. Mortice the frame for the strike box and fit the strike plate. Test the latch and deadbolt engagements — both should feel positive without requiring force.
Step 10 — Weatherstripping. Compression seals should be fitted to the head, hinge side and latch side of the frame before the door is finally closed up. The seal should compress evenly when the door is shut. For the threshold, fit an appropriate threshold bar or draught excluder — the type depends on the floor level relationship between inside and out, and whether a low-threshold (wheelchair-accessible) detail is required.
Step 11 — External sealing. Apply a bead of low-modulus silicone sealant between the frame and the external masonry reveal, and between the frame and the internal plaster. This prevents water ingress at the frame perimeter — a common cause of frame rot that is not visible until significant damage has occurred.
Common Mistakes
- Hanging with two hinges. Three 100 mm hinges are the minimum for a full-size exterior door. Two will cause sagging and frame distortion within a year.
- Not pilot-drilling timber. Driving hinge screws without pilot holes into hardwood stiles risks splitting the door. In softwood frames, over-driving screws strips the thread; countersink properly.
- Ignoring the threshold. A well-hung door with a leaking threshold will still produce draughts and water ingress. The threshold detail deserves as much attention as the hanging.
- Not notifying building control. Replacing an exterior door in a house requires either a Competent Person certificate or a local authority notification. Many homeowners are unaware of this and only discover it during conveyancing.
- Mismatching door and frame hand. Confirm the handing (which side the hinges are on, viewed from outside) before ordering. Reversing a door costs time and sometimes money if the door is pre-bored for hardware on the wrong side.
Pro Tips
- A hinge jig is worth the £20–£40 investment for any door hanging job. It removes guesswork from the most precision-critical stage of the process.
- For composite doors with multipoint locking, the lock adjustment screws on the gearbox are the primary fine-tuning tool for door alignment — use them before reaching for the plane.
- In exposed locations, apply end-grain sealer to any timber door at the top and bottom edges, even if the door is pre-primed. End grain absorbs moisture fastest and is the most common starting point for rot.
