Summary

Patio doors (sliding, French and bifold) are one of the largest individual ticket items a window and door installer quotes. The price spread is wide because the category covers everything from a basic 2-pane UPVC slider at £1,800 to a premium 5-pane aluminium bifold at £12,000. The differentiator isn't the door — it's the structural opening, the U-value/Part L compliance, the threshold detailing, and the access for installation.

For installers, the biggest pricing risks are: assuming a like-for-like replacement is straightforward when the existing opening needs widening (structural lintel work), underestimating the time to make the threshold weathertight and DDA-compliant on level-access designs, and missing the FENSA / Building Regs sign-off cost in the quote (around £40-£90 per certificate).

The single biggest margin opportunity is on aluminium bifold and slim-frame slider doors — the materials are 2-3x the cost of UPVC, but the customer perceives them as a premium product and accepts higher pricing without comparison-shopping. UPVC remains the most price-sensitive product category in this sector.

Key Facts

Quick Reference Table — Typical Pricing

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Door Type Configuration Material Price Range (Supply + Fit)
Patio slider 2-pane, 1800mm wide UPVC £1,800–£2,800
Patio slider 2-pane, 2400mm wide UPVC £2,200–£3,400
Patio slider 2-pane, 3000mm wide UPVC £2,800–£4,200
Patio slider 2-pane, 2400mm wide Aluminium £3,500–£5,800
French doors Pair, 1800mm UPVC £1,500–£2,500
French doors Pair, 1800mm Aluminium £2,800–£4,500
Bifold 3-pane, 2400mm UPVC £2,800–£4,200
Bifold 3-pane, 2400mm Aluminium £3,500–£5,800
Bifold 4-pane, 3600mm Aluminium £5,500–£8,500
Bifold 5-pane, 4800mm Aluminium £7,500–£12,500
Lift-and-slide 2-pane, 3000mm Aluminium £6,500–£11,000
Lift-and-slide 3-pane, 4500mm Aluminium £9,500–£18,000
Cost Component Typical Trade Cost Notes
UPVC slider 2-pane 2.4m supply only £900–£1,400 Mid-market
Aluminium bifold 3-pane 2.4m supply only £2,200–£3,500 Trade price from supplier
Aluminium bifold 4-pane 3.6m supply only £3,500–£5,500 Premium brands higher
Glazing — triple glazed upgrade +£300–£800 Per door
Cill, lintel, weather-bar materials £80–£250 Per install
Steel lintel (for new openings) £150–£450 + structural calc
FENSA / Certass certificate £25–£40 Per certificate
Skip + waste disposal £180–£300 Per house
Scaffolding (rare) £400–£900 Only on tall openings

Detailed Guidance

Site visit and survey

Always do a measure-up site visit. Bifolds and large sliders cannot be quoted off a photo:

PATIO DOOR SURVEY CHECKLIST
===========================
□ Existing opening width × height (brick-to-brick + frame-to-frame)
□ Structural opening (with lintel) confirmed
□ Cavity wall or solid wall construction
□ Existing threshold height and floor type
□ Inside floor level vs outside ground level
□ DPC location and condition
□ Cill type and weather-bar
□ Access route for new door (driveway, garden, side passage)
□ Crane / lifting required for large bifolds?
□ Existing electrics in opening (alarms, security lights)?
□ Internal finishes — plaster, tiling, skirting reinstatement?
□ External finishes — render, brick, weatherboard reinstatement?
□ Window above/beside — disturbance during install?

Bifold panels weigh 30-80kg each — for a 5-pane the panels alone are 250-400kg, plus the head track and threshold. Larger installs may need 4-person lift or a small crane.

The structural-vs-replacement decision

This is the single biggest pricing variable:

Existing Opening Action Cost Implication
Same size as new door Like-for-like replacement No structural cost
Slightly smaller (≤200mm) Pack out / extend frame +£100-£300
Significantly smaller New lintel, structural opening +£800–£2,500
Window converted to door New lintel + threshold + sub-cill +£1,200–£3,500
Solid wall to opening Major structural work +£2,500–£6,500 + structural engineer

Any new or widened opening triggers Building Regulations Part A and likely a structural calculation by an engineer (£250-£500). Include this as a separate line item, not buried in the door price.

Labour breakdown

A typical 2-pane UPVC slider replacement:

Phase Hours Notes
Remove old door 1.5 Including glass
Prep opening, fit cill 1.5 Level, plumb
Install frame, fix to brickwork 2 4-6 fixings per side
Hang doors, fit track, glaze 2 Sliders shipped pre-glazed
Seal, foam, weather-bar 1 External silicone, foam between frame and brick
Internal finishes (architrave, skirting) 1 Make good
External finishes (silicone, cill) 1 Make good
Test operation, hand-over 0.5 Demonstrate locks, maintenance
Total 10.5 hrs One full day for 2-person crew

A 4-pane aluminium bifold takes 1.5-2 days for the same crew, mainly due to track precision and panel alignment.

Where the margin sits

Threshold detailing — the source of most callbacks

Level-access (DDA-compliant) thresholds look great but are the source of most water-ingress complaints if not detailed correctly.

LEVEL-ACCESS THRESHOLD — SECTION
================================

OUTSIDE              INSIDE
  ▲                    ▲
  │                    │
  │  ┌──────────┐      │
  │  │          │      │
══════════════════════════ Internal floor level
  │  │ THRESHOLD│      │
  │  │   ≤10mm  │      │
══════════════════════════ External level
   ▲ ▲ ▲ ▲ ▲ ▲          
   French drain         
   (linear, sloped to outlet)
   60mm wide × 100mm deep

Key rules:

Get this wrong and the customer will be back within 6 months saying water came through. Build the channel into every level-access install quote.

FENSA / Certass / DGCOS certification

For replacement windows and doors, the installer registers the work with a Competent Persons Scheme:

The certificate goes to the homeowner and to Local Authority Building Control, and is required for:

Always include the cost in the quote — never absorb it. £40-£60 is a clearly separable line item.

Frequently Asked Questions

Do I need planning permission for patio doors?

Replacement doors and windows in an existing opening are permitted development and don't need planning permission, unless the property is listed or in a conservation area, or unless the work changes the appearance of a property in a designated area. New openings (converting a wall to a door, or significantly widening) may need planning permission if they change the external appearance — check with the local authority before quoting.

What U-value should I quote for?

For all replacement glazing in England since June 2022, the minimum is 1.4 W/m²K (Part L). Most mid-market doors achieve 1.2-1.4 W/m²K with standard glazing. Triple glazing or "warm-edge" spacer bars take the U-value down to 0.8-1.0 W/m²K — premium territory. The customer cares about the EPC impact (which is real but small for a single door) and noise reduction (which is significant); pitch both benefits, not the U-value number itself.

How do I quote for bifold doors over a kitchen extension?

The door is the single most expensive item in the extension and the most visible feature. Get the supplier to provide a CAD drawing showing the door in context. Quote: door supply (cost + 30-50%), install (1.5-2 days at full day rate), structural lintel and steel (separate, with calc), threshold detailing including any external drainage channel, make-good of internal plaster and external render, and FENSA certificate. Total typically £5,500-£12,000 for a 3-4m bifold on a typical kitchen extension.

Can I install a patio door myself (DIY) and get FENSA later?

No. FENSA only certifies its registered installers. A DIY-installed door requires a Building Notice to Local Authority Building Control before installation, an inspection by a Building Control officer, and a compliance certificate from the council. The total cost (BCO fees + your own time) is typically £200-£400 plus the installer-priced labour you've not saved. The "DIY + FENSA later" route does not exist.

What's the difference between bifold and lift-and-slide?

Bifolds fold concertina-style and stack to one or both sides. Maximum opening of 90-95% of the door's nominal width. Each pane is hinged. Lift-and-slide doors slide horizontally on a heavy-duty track — a single lever lifts the door slightly off the track, allowing it to glide. Maximum opening of 50% (one pane slides behind the other) or 67% (3-pane with 2 sliding). Lift-and-slide is quieter, more weathertight, and premium-priced. Bifold gives a more dramatic "open the whole wall" feel. Customer choice; both are valid for kitchen extensions.

Regulations & Standards