Bifold doors, sets of two or more panels that fold and stack to one or both sides of an opening, are one of the most requested features in rear extension and kitchen renovation projects. They create a wide, unobstructed opening between the interior and garden, and their sleek frames photograph well. But they come at a price, they have practical limitations, and they are not always the best choice for every opening.

What Do Bifold Doors Cost?

Costs split into supply-only and supply-and-fit. Most homeowners have them installed as part of a wider project, so the labour is bundled into the build cost. If you are replacing like-for-like on an existing opening, expect to pay a joiner around £250–£350 per day for installation (a specialist door fitter may charge more), with a standard 3-panel set taking one to two days.

ConfigurationWidthSupply-Only Cost
2-panel, uPVC1.2 – 1.8 m£900 – £1,800
3-panel, aluminium2.1 – 2.7 m£2,200 – £4,000
4-panel, aluminium2.7 – 3.6 m£2,600 – £5,5001
5-panel, aluminium3.6 – 4.8 m£4,000 – £7,500
6-panel, timber3.6 – 5.4 m£5,000 – £9,000+
Full-width spanning 5 m+Various£7,000 – £15,000+

Prices are for thermally broken frames with double glazing. Triple glazing adds roughly 15–25% to the supply cost.

Standard Bifold Door Sizes

Bifold doors are made to bespoke dimensions, but panel sizes fall within fairly consistent limits:

  • Panel width: Origin, for example, makes leaves from 400 mm to 1,200 mm wide; narrower leaves mean more frames in the view, and wider ones are heavier to fold2
  • Heights: most domestic sets are around 2,100 mm high, and panels up to about 3,000 mm high are available2
  • Overall width: Origin makes sets of up to ten doors, for openings from 1,400 mm to 9,000 mm wide and above; a wide opening in a loadbearing wall needs a lintel or steel beam above it, sized by a structural engineer2

For most UK rear extensions, openings of 2.4 m to 4.2 m with 3 to 5 panels are the most practical and cost-effective configurations.

Material Comparison

MaterialProsConsTypical Frame Depth
Aluminium (thermally broken)Slim sightlines, durable, low maintenance, wide colour choiceHigher cost than uPVC70–100 mm
uPVCCheapest option, good thermal performanceBulkier frames, limited colours, can warp over time90–120 mm
TimberWarm aesthetic, FSC-certified options available, paintableHigher maintenance, susceptible to moisture80–120 mm
Timber-aluminium (hybrid)Timber interior, aluminium exterior, best of bothMost expensive option90–120 mm

Aluminium is a popular choice in new-build and high-end renovation in the UK because the thermally broken frames are slim, very durable, and available in a wide range of RAL colours to match the house. Origin’s aluminium bifold frames, for example, are 75 mm deep front to back.2

Building Regulations and Glazing Standards

Any new or replacement external door (including bifolds) in England must meet the requirements of Approved Document L (Conservation of Fuel and Power); Wales publishes its own version.3 Key thermal requirements for 2026:

  • Whole-door U-value: ≤1.4 W/m²K for a new or replacement door in an existing home; the limiting value for a door in a new dwelling is 1.6 W/m²K, but a new dwelling must also meet whole-house energy targets3
  • Doorset Energy Rating: for a door whose internal face is more than 60% glazed, as a bifold is, Approved Document L accepts a Doorset Energy Rating of Band C or better as the alternative to the 1.4 U-value.3 The Window Energy Rating is for windows, not doors3
  • Safety glazing: all panes within 1,500 mm of the finished floor level (and, in side panels, within 300 mm of the door edge) must be toughened or laminated safety glass to BS EN 12600 (Class 3, or Class 2 where the pane is wider than 900 mm)4
  • Air permeability and water tightness: better-quality systems are rated to Class 4 air permeability under BS EN 12207 and Class E1200 water tightness under BS EN 12208, ask suppliers for their test ratings56

A replacement door can be fitted by an installer registered with a competent person scheme, who certifies that the work complies without involving building control; otherwise the work needs building control approval.7 For a new or widened opening (as opposed to a replacement), the structural work also needs Building Regulations approval, and the lintel or steel beam over a wide opening in a loadbearing wall is normally specified by a structural engineer.8

Alternatives to Bifold Doors

Bifolds are not the only way to open up a rear elevation. The main alternatives are:

Sliding patio doors (including lift-and-slide): panels slide on tracks rather than folding. They take up less floor space when open, put fewer frames in the view when closed, and can perform better thermally at the same price point. The trade-off is that at least one panel is always behind another, so the opening is never fully clear.

French doors: a classic two-panel outward-opening configuration. Excellent thermal performance, simple mechanism, lower cost (typically £1,200–£3,500 supply-and-fit for aluminium or timber), but the opening is limited to the width of two leaves, typically up to about 1.8 m.

Pivot doors: a single large panel on a central pivot, creating a dramatic full-width opening. Expensive (£5,000–£20,000+) and better suited to large openings in contemporary properties.

Frameless glass walls: structural glass systems with minimal framing, moving into architectural glazing territory. Costs start around £2,000/m² and rise steeply. Requires specialist structural design.

Which Option Is Right for You?

  • Choose bifolds if you want most of the opening to disappear and have enough patio space for the folded stack (the folded panels stand out from the frame by roughly the width of one panel).
  • Choose sliding doors if thermal performance and a less interrupted view when the doors are closed are the priority, or if the opening exceeds 5 m.
  • Choose French doors if the opening is 1.2–1.8 m and budget is tight.

What to Ask a Supplier

  1. What is the whole-unit U-value (not just centre-pane)?
  2. What are the air and water tightness class ratings?
  3. Is the frame thermally broken, and what is the thermal break material?
  4. What is the maximum span before an intermediate post or support is needed?
  5. What guarantees do you offer on the hardware and seals?

Compare guarantees as well as prices: many suppliers offer ten years or more on the frame and shorter terms on hardware such as rollers and locks.

Summary

Bifold doors are a genuinely useful product for rear openings of 2.4 m to 5 m, but the cost and the space they demand when open are real limitations. For most standard openings, aluminium thermally broken bifolds at the mid-price range, £3,000–£6,000 supply-and-fit for a 3 or 4-panel set, represent good value. Always check U-values and test ratings, not just the price per panel.

References (8)

Figures in this note were checked against the sources below on 2 October 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1costsupplier figureWickes.RN-3IEM3HA price, true at 2026-09. Wickes's published price for the item the cost register files as "benchmark: aluminium bifold door, three panel, around 3 m wide", which is the figure a cost footnote on this page points at.
  2. 2technicalsupplier figureOrigin, guidance.RN-4QQUNDA UK bifold maker's product FAQ. It gives its minimum and maximum leaf widths, maximum panel height and the largest set it makes.
  3. 3technicalvery strongMinistry of Housing, Communities and Local Government.RN-L0FCJXThe in-force U-value tables a DIY insulation or door note must quote, with the exact numbers. Table 4.2, limiting U-values for new fabric elements in existing dwellings, sets roof 0.15, wall 0.18, floor 0.18, swimming pool basin 0.25, window 1.4 or Window Energy Rating Band B minimum, rooflight 2.2, doors with more than 60 per cent of the internal face glazed 1.4 or Doorset Energy Rating Band C minimum, and other doors 1.4 or Doorset Energy Rating Band B minimum. Table 4.3, for existing elements, gives a roof threshold of 0.35 and an improved value of 0.16, which is the figure a loft insulation note needs: paragraph 4.12 says a retained element whose U-value is higher than the column (a) threshold, for example through a loft or garage conversion, should be upgraded to the column (b) value. Paragraph 4.13 allows a lesser upgrade only where the improved value is not technically or functionally feasible or would not achieve a simple payback of 15 years or less. Paragraph 4.8 requires a replacement element to be no worse than the one it replaces as well as meeting Table 4.2. Paragraph 4.10 gives the heritage exception: where character must be maintained, a centre pane U-value of no more than 1.2 or low-emissivity secondary glazing. Note 9 records that the timber window concession of 1.6 or Band C ended on 14 June 2023. The 2021 edition came into force on 15 June 2022; a 2026 edition exists at https://assets.publishing.service.gov.uk/media/69c122a6cfa346b9d4704a55/ADL1_2026.pdf.
  4. 4technicalvery strongMinistry of Housing, Communities and Local Government.RN-XH6E39The standard that decides whether a loft ladder is legal and when a raised deck needs a balustrade. Published 3 January 2013, it covers protection from falling, collision and impact including stairs, ladders, ramps, guarding and vehicle barriers. Paragraph 1.31 states that retractable ladders must not be used as a means of escape. Paragraph 1.32 permits a fixed ladder, with fixed handrails on both sides, only for access in a loft conversion containing one habitable room, and only where there is not enough space without altering the existing space for a compliant stair, which is the rule that catches most loft ladder installations. Paragraph 1.29 restricts alternating tread stairs to loft conversions. For a private stair the maximum pitch is 42 degrees (Table 1.1 note 1), the normal relationship between rise and going is twice the rise plus the going between 550mm and 700mm, and for dwellings external tapered steps forming part of the building need a going of at least 280mm. Paragraph 3.1 requires guarding wherever it is reasonably necessary for safety at the edge of a floor, gallery, balcony, roof, light well, basement or similar sunken area. Paragraph 3.2 requires guarding to be at least the height in Diagram 3.1, allows any wall, parapet or balustrade to serve as guarding, and requires it to resist the loads in BS EN 1991-1-1 with its UK National Annex and PD 6688-1-1, with BS 6180 for barrier and infill panel design. Handrails should be positioned 900mm to 1000mm from the pitch line or floor.
  5. 5technicalstrongBSI Knowledge, a standard.RN-ECESDKBS EN 12207:2016, the air permeability classification for windows and doors, Class 1 to Class 4. The tested figure behind a claim that a window is draughtproof, and one of the three performance classes, with watertightness and wind resistance, that a window should be declared against.
  6. 6technicalstrongBSI Knowledge, a standard.RN-D9GQYABS EN 12208:2000, the watertightness classification for windows and doors, tested by spraying water at increasing pressure until it leaks. Produces the class letter and number a window's declared performance quotes, which is what matters on an exposed elevation where driving rain, not cold, is the problem.
  7. 7technicalvery strongPlanning Portal, guidance.RN-33F8DPThe Planning Portal on building regulations for doors and windows: since 1 April 2002 the regulations have applied to all replacement glazing, covering thermal performance, safety glazing, means of escape and ventilation. That 2002 date is the one that matters at sale, because it is when a FENSA certificate or a building regulations notice started being expected for replacement windows.
  8. 8technicalvery strongThe National Archives, legislation.RN-ZCMRHVRegulation 3 of the Building Regulations 2010, the meaning of building work. Lists what counts: erecting or extending a building, providing or extending a controlled service or fitting, material alteration, work required by a material change of use, and inserting insulation into a cavity wall. If a job is not on this list it is not building work, so this is the first place to check whether approval is needed at all.

  1. LPD Aluvu Anthracite Grey Left Hand External Bi Fold Door Set 3590 x 2128mm, Wickes, accessed 2 October 2026. Priced at 2026-09, so no calibration is needed. wickes.co.uk

  2. Origin’s experts answer your FAQs about bi-folding doors, Origin, accessed 29 September 2026. origin-global.com

  3. Approved Document L: Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments, HM Government (GOV.UK), accessed 7 September 2026. assets.publishing.service.gov.uk

  4. Approved Document K: Protection from falling, collision and impact, 2013 edition, HM Government (GOV.UK), accessed 7 September 2026. assets.publishing.service.gov.uk

  5. BS EN 12207:2016 Windows and doors. Air permeability. Classification, BSI Knowledge, accessed 7 September 2026. knowledge.bsigroup.com

  6. BS EN 12208:2000 Windows and doors. Watertightness. Classification, BSI Knowledge, accessed 7 September 2026. knowledge.bsigroup.com

  7. Doors and windows: Building regulations, Planning Portal, accessed 29 September 2026. planningportal.co.uk

  8. The Building Regulations 2010, regulation 3: Meaning of building work, legislation.gov.uk, accessed 2 October 2026. legislation.gov.uk