How to Price Bifold and Sliding Door Installation: Supply, Fit and Reveal Costs
Quick Answer: A 3-pane aluminium bifold (3,000mm wide) typically prices at £4,500–£7,500 supply-and-fit in 2026; a 4-pane runs £6,000–£9,500; a sliding patio door (2,400mm two-pane) £3,800–£6,500. Build the quote bottom-up: supply, structural opening (steel beam, lintel, padstones), fit labour (2 days for two fitters), threshold detail, internal reveal making good, and floor finishing. Door supply alone is rarely more than 60% of the cost on a typical job — opening-formation, structural and finishing always add at least 25–35%.
Summary
Bifold and sliding door installs are the second-most lucrative product line for a domestic glazing fitter (after window replacement in volume) but they are the most exposed to underquoting. The frame and glass is only one of seven cost zones — the others are structural opening, lintel/beam, threshold and drainage, internal reveal making good, electrics if trickle vents or smart locks are specified, and external paving level adjustment. Quotes that ignore any of these come in £1,500–£4,000 short of cost.
In 2026, aluminium bifold supply prices are stable but threshold accessories (low-line aluminium, retractable seals, integrated drainage) have climbed 15–22% as suppliers move to thermally-broken frames to meet the U-value 1.4 W/m²K replacement threshold under Approved Document L1B. Sliding doors with slim sightlines (Origin OS-77, Schueco AS PD 75, Smart Visofold equivalents) command £8,000–£15,000+ and have lead times of 6–10 weeks. Standard bifolds from volume manufacturers run 4–6 weeks.
Key Facts
- Trade discount on aluminium bifold frames — 25–35% off retail through Origin, Schueco, Reynaers and Smart Systems trade channels; 35–45% on full-installer accounts
- U-value compliance — replacement bifolds must achieve 1.4 W/m²K whole-door or WER Band B (Approved Document L1B 2022). New build 1.2 W/m²K
- Approved Document Q — new dwellings require PAS 24:2016 enhanced security on bifolds
- Door supply lead time — 4–6 weeks volume manufacturers, 6–10 weeks slim-sightline architectural suppliers
- Fit time — 2-pane sliders 1 day for two fitters, 3-pane bifolds 1.5 days, 4–7 pane runs 2–2.5 days; longer if structural beam and threshold detail are part of scope
- Structural opening cost — RSJ 152×89×16 (4m): £400–£650 supply, £350–£550 install, £150–£300 padstone build-up, £150–£300 making good — total typically £1,200–£1,900
- Threshold types — flat (low-rise, no-trip <8mm rise, premium £180–£350 over standard), weathered (15–25mm step, standard), oversail (50mm — not Part M compliant for new build)
- Approved Document M (volume requirement) — flat threshold for accessibility in new dwellings; not retrospective on replacements
- Floor level adjustment — typically £400–£1,200 across the doorset where internal screed differs from external paving
- Glass per leaf — bifold leaves are typically 600–900mm wide; weight rises ~15–22kg per leaf with double glazing, hence the importance of correctly sized hinge and roller carriages
Quick Reference Table — UK Trade Supply Costs 2026
Spending too long on quotes? squote turns a 2-minute voice recording into a professional quote.
Try squote free →| Product | Width × Height (mm) | Configuration | Trade supply | Supply + fit + opening | Notes |
|---|---|---|---|---|---|
| Aluminium bifold | 2,400 × 2,100 | 3-pane | £2,200–£3,400 | £3,800–£6,000 | Standard kitchen-to-garden |
| Aluminium bifold | 3,000 × 2,100 | 3-pane | £2,800–£4,000 | £4,500–£7,500 | Most common 3-bed semi extension |
| Aluminium bifold | 3,600 × 2,100 | 4-pane | £3,400–£4,800 | £5,500–£8,800 | Larger family kitchen |
| Aluminium bifold | 4,200 × 2,100 | 5-pane | £4,200–£5,800 | £6,500–£10,500 | Single-storey rear extension |
| Aluminium bifold | 5,400 × 2,100 | 6-pane | £5,500–£7,500 | £8,500–£14,000 | Premium architectural |
| Aluminium bifold (slim sightline) | 3,000 × 2,100 | 3-pane | £4,800–£6,500 | £6,800–£10,500 | Origin OB-72, Reynaers SlimLine |
| UPVC bifold | 2,400 × 2,100 | 3-pane | £1,400–£2,000 | £2,800–£4,500 | Lower spec, residential only |
| Sliding patio door (2-pane) | 2,400 × 2,100 | XO | £1,800–£2,800 | £3,000–£5,000 | Standard inline slider |
| Sliding patio door (2-pane) | 3,000 × 2,200 | XO | £2,400–£3,400 | £3,800–£6,500 | Most common kitchen wall |
| Sliding patio door (3-pane) | 4,500 × 2,400 | OXX | £4,500–£6,500 | £7,000–£11,500 | Large rear opening |
| Slim sliding (Schueco AS PD 75) | 3,000 × 2,400 | 2-pane | £6,500–£9,500 | £9,000–£14,500 | 30mm sightline, premium |
| Lift-and-slide | 4,500 × 2,400 | OXX | £8,500–£12,500 | £12,500–£18,500 | Heavy-duty mechanism |
| Pivot door (single) | 1,200 × 2,400 | Single-leaf | £4,800–£7,500 | £6,500–£9,500 | Architectural feature |
Frame prices include thermally broken aluminium, double-glazed sealed unit, and stock RAL or anthracite finish. Premium colours (matt, dual-colour) typically add £150–£400 per door set.
Detailed Guidance
The seven cost zones of a bifold or slider quote
- Door supply — frame, glass, hardware, threshold accessories, trickle vents (if required), and stock or specified colour
- Structural opening formation — knock-out, RSJ supply and install, padstones, lintel, brickwork over and reinstatement
- Threshold detail — low-rise vs weathered threshold, drainage channel for flat-threshold installs, mastic seal under aluminium cill
- Fit labour — two-man crew, allow 1–2.5 days depending on door size and structural complexity
- Internal reveal making good — plaster reveal, MDF or hardwood architrave, skirting return, floor finish trim
- External make-good — render or brick patching at jamb returns, lead apron at structural opening if abutting a flat roof
- Floor level / threshold drainage — paving step or stepped threshold formation if internal floor and external paving differ in level
A 3-pane 3m bifold without structural opening typically runs £4,500–£6,000. The same door with a new structural opening (RSJ, padstones, plaster, threshold drainage) typically runs £6,500–£8,500.
Structural opening — when do you need a steel beam?
For internal-to-garden bifold installs replacing existing French doors of similar width: usually no new beam needed if the original lintel is sound and the load path is unchanged. For new openings (knocking out a kitchen rear wall to fit a 3.6m bifold): always a steel beam, sized by a structural engineer.
Typical structural fees:
- Structural engineer's calc: £350–£750 for single-beam domestic
- RSJ supply (152×89×16, 4m): £400–£650
- Padstones (typically 3 courses solid blockwork or precast concrete padstones): £150–£300 supply
- Beam install labour (two-man, includes propping and reinstatement): £600–£900
- Brickwork/blockwork over (where beam is shallow and walling continues above): £150–£400
- Plastering both sides: £200–£450
Total structural opening adds £1,650–£3,400 to a typical quote.
Threshold types and Part M accessibility
Three threshold options:
- Flat (no-step) — premium thermal break aluminium with retractable rain seal. Required by Approved Document M for new dwellings. Best for level patio access. Adds £180–£350 over standard.
- Weathered (low-rise) — typically 15–25mm step. Standard issue. Best for replacements where internal floor sits above external paving.
- Oversail (50mm) — used where there's a significant level difference. Not Part M compliant. Avoid in new dwellings.
For replacement work in existing properties, weathered is the default and Part M doesn't apply retrospectively. For new dwellings or single-storey extensions where the paving and internal floor will be levelled together, specify flat threshold and confirm the drainage detail with the client.
Drainage at flat thresholds — the most-missed detail
Flat-threshold bifolds and sliders need drainage in front of them. Without it, water sits on the threshold seal, ingresses past the rain bar, and ruins the threshold and adjacent flooring. Standard solutions:
- Heelguard linear drain (50–100mm wide channel, ACO or equivalent) connected to surface water drain — £150–£280 supply, £200–£400 install per linear m
- French drain with gravel and geotextile — £80–£150 per linear m, lower spec but acceptable for non-critical
- Threshold pan (bespoke aluminium) — built into the door supply, +£200–£400 added
Always include drainage on flat-threshold quotes. It's one of the biggest sources of post-handover complaints.
Glass and security upgrades
Default spec is 4-20-4 toughened double glazing with low-e coating. Common upgrades:
- Acoustic glass — laminated 6.4mm + 4mm with 16mm argon, +£60–£120/m². Specify on roadside elevations.
- Solar control glass — low-g glass for south-facing apertures, +£35–£70/m². Approved Document O (overheating) compliant.
- Triple glazing — 4-12-4-12-4, +28–40% on glass cost. Compatible only with thicker frame profiles (Origin OB-49, Reynaers SL 60).
- PAS 24:2016 enhanced security — multi-point locking, anti-lift devices, Secured by Design accreditation, +£250–£450 on hardware
Bifold vs sliding — which to recommend?
The choice usually comes down to:
| Factor | Bifold | Sliding |
|---|---|---|
| Maximum opening | Full opening (95%+) | Half opening (50%) |
| Sightlines | Wider mullions (60–80mm) | Slimmer (30–50mm) |
| Threshold | Bigger track | Cleaner aesthetic |
| Cost (3m, 2026) | £4,500–£7,500 | £3,800–£6,500 |
| Maintenance | More moving parts | Simpler track and rollers |
| Best for | Indoor-outdoor entertainment | Daily use, garden views |
For a south-facing garden with regular entertaining: bifold. For a north-facing, less-used garden where view matters more than maximum opening: sliding.
Frequently Asked Questions
How long does a bifold installation take?
Door fit alone for a standard 3-pane in an existing opening: 1–1.5 days for two fitters. With structural opening formation: 3–4 days minimum. Threshold drainage, internal making-good, floor finishing and external rendering add another 2–4 days, especially if you're working sequentially with other trades.
What's the cost of bifold doors for a UK 3-bed kitchen extension (homeowner-friendly)?
For a typical UK 3-bed home adding a kitchen extension with a 3m aluminium bifold door, expect total bifold cost £4,500–£7,500 supply-and-fit in 2026. Cheaper UPVC bifolds £2,800–£4,500 but rarely match the look. Slim-sightline architectural sets (Origin, Schueco, Reynaers) £6,500–£10,500. Allow another £1,500–£3,000 for the structural opening if the wall is being knocked out, plus drainage and floor levelling. Always get itemised quotes — total cost should be £6,000–£10,000 for a standard door + opening package on a 3-bed extension.
Do I need planning permission for a bifold door in a rear elevation?
Usually no — bifold doors fit within Permitted Development Rights for replacement and minor alteration on most domestic properties. Planning is required only where: the property is in a Conservation Area with Article 4 restrictions, the property is Listed (any change to fabric needs Listed Building Consent), or the bifold is part of an extension requiring its own planning application. Confirm before quoting. The customer is liable, but installer reputation suffers when post-installation enforcement is served.
What's the lead time difference between volume and architectural manufacturers?
Volume aluminium bifold manufacturers (Smart Systems, Aluk, Liniar UPVC) — 4–6 weeks. Specialist slim-sightline manufacturers (Origin, Reynaers, Schueco, Visofold) — 6–10 weeks for stock products, 12–16 weeks for non-standard sizes or colours. Always confirm lead time before signing customer contract — slipped lead times are the most common reason fitters lose deposits to customer cancellation.
What goes wrong most often on a bifold install?
Top three failures: (1) under-specified structural beam — the engineer's calc was based on assumed loading and the actual loading was higher, beam deflects, doors stick. (2) Threshold drainage missed or under-spec — water pools on flat threshold, leaks into floor build-up. (3) Frame goes in out of square — even 3–5mm twist causes the locking mechanisms to bind. Always lift the frame onto packers, level perfectly across all axes, and re-check after every fixing.
Regulations & Standards
Approved Document L1B (2022) — replacement door U-value 1.4 W/m²K
Approved Document M (Access to and use of buildings) — flat threshold required in new dwellings, not retrospective
Approved Document Q (Security) — PAS 24:2016 mandatory in new dwellings
Approved Document K (Protection from falling, collision and impact) — safety glass in critical locations
Approved Document O (Overheating, 2022) — solar gain assessment for new dwellings; bifold and slider sets often trigger compliance steps
BS 6262-4 — code of practice for safety glass in critical locations
BS EN 14351-1 — windows and external pedestrian doors product standard
BS 8213-4 — survey and installation of windows and doorsets
PAS 24:2016 — enhanced security performance
CDM Regulations 2015 — domestic project responsibilities
Approved Document L1B — Conservation of fuel and power, existing dwellings
Approved Document M — Access to and use of buildings (volume 1: dwellings)
PAS 24:2016 — enhanced security performance for windows and doors
window replacement pricing — package quoting alongside doors
single-storey extension build-up — common scope including bifold supply
steel beam supply and install costs — structural opening element
FENSA self-certification routes — required for bifold and slider replacements