The complete bifold door buying guide

1. Material — the first and biggest choice

Bifold doors come in three materials: aluminium, uPVC and timber. Each has a clear best-fit use case.

Aluminium — the default choice for new installations

Pros: slimmest sightlines (70mm visible frame between panels), largest possible panel widths (1.2m max), 25–30 year service life, any RAL colour, recyclable. Cons: more expensive than uPVC, needs thermal-breaking for good U-values (which all modern systems have).

Best for: modern extensions, kitchen-diners, any installation where slim frames matter, contemporary aesthetics.

uPVC — the budget choice

Pros: roughly 30–40% cheaper than aluminium, excellent thermal performance (uPVC is naturally insulating), no maintenance, available in many foil finishes. Cons: chunkier frames (100mm sightlines typical), smaller maximum panel widths (1m), 20–25 year service life, can yellow slightly with UV over decades.

Best for: refurbishments, family homes, conservatories, budget-conscious projects where slim sightlines aren't critical.

Timber — the period/listed choice

Pros: traditional appearance, often the only option permitted in listed buildings and conservation areas, longest service life (40–60 years), best natural thermal insulation. Cons: highest upfront cost, requires re-finishing every 8–10 years, dimensional movement with humidity (mitigated by using engineered timber).

Best for: period properties, listed buildings, conservation areas, barn conversions, properties where character matters more than minimal sightlines.

2. Sizing the opening

The opening width drives panel count, but it's not a strict formula — the same width can be configured multiple ways depending on what you want.

Opening width	Typical panel count	Notes
1.8–2.4m	2–3 panels	Smallest practical bifold
2.4–3.0m	3 panels	Most popular for smaller extensions
3.0–4.0m	3–4 panels	Standard for kitchen-diner extensions
4.0–5.0m	4–5 panels	Substantial installation
5.0–6.0m	5–6 panels	Large openings, often with traffic door
6.0m+	6–7 panels	Heavy installation; structural support critical

Above 6m you should also consider whether a corner bifold (two sets meeting at a 90° corner with no post between them) or a combined bifold-and-slider arrangement might serve better. Both add architectural drama but also cost and complexity.

3. Configuration — which way they open

Bifolds can open inwards or outwards, and they can stack to the left, the right, or both ways from the centre.

• Opening outwards (most common): panels swing out into the garden. Preserves internal floorspace. Requires unobstructed exterior space for the stacked panels.
• Opening inwards: panels swing into the room. Useful when external space is limited (balconies, narrow patios). Takes up floor space when open.
• Stacking left or right: panels fold to one side only. Simplest, lowest cost, allows for an integrated traffic door.
• Dual-stacking: panels split and fold to both sides from the middle. More balanced appearance, no traffic door possible.

Traffic doors

A traffic door is one panel that operates independently as a normal hinged door — for everyday use without folding the whole set. Highly recommended for installations used daily. Typically the leftmost or rightmost panel; specified at survey stage.

4. Glazing

Double glazing is standard. Most bifold systems achieve good U-values with quality double glazing — triple glazing is only worth specifying for Passivhaus projects, very exposed locations, or where regulatory requirements demand it.

Glass options to consider:

• Solar control glass for south-facing installations — prevents summer overheating, mandatory in some specifications
• Acoustic glass for properties facing busy roads or airports
• Self-cleaning glass — Pilkington Activ — for upper-floor or hard-to-reach installations
• Privacy glass — obscure, frosted, or switchable — for overlooked installations
• Safety glass — laminated or toughened — mandatory in any panel below 800mm from floor level

5. Threshold

The threshold is the bar that sits at the bottom of the door, between the room and the outside. Two main choices:

Standard rebated threshold (50mm step up): best weathertightness rating (Class 4 air permeability), traditional appearance, but creates a step that's a trip hazard and impassable to wheelchairs.

Low-profile threshold (5–10mm step): near-flush transition between inside and outside, satisfies Part M accessibility, ideal for indoor-outdoor flowing schemes. Slightly reduced weatherproofing performance (Class 3 vs Class 4) — academic for most UK locations.

For new installations we recommend the low-profile threshold in almost all cases. The Class 3 vs Class 4 difference is irrelevant unless you're in a very exposed coastal location.

6. Hardware and security

Modern bifolds use multi-point hook locks on every panel. The standard you want to specify is PAS 24 — this is the UK security certification required by Secured by Design and Approved Document Q for new builds. PAS 24 bifolds are as secure as any other modern external door.

For insurance purposes, mention PAS 24 to your provider when changing external doors. It usually satisfies any security clause without requiring further specification.

7. Choosing an installer

Three signals to look for:

1. FENSA or CERTASS registration. This is the self-certification scheme for window and door installations — it means the installer can sign off your building regs without involving the council. Non-registered installers are workable but you'll need to arrange building control separately.
2. Directly-employed installers, not subcontractors. Ask the question directly. Subcontracted installation crews have rotating quality; directly-employed teams have continuity and accountability.
3. A specialism, not a generalist. Companies that install windows, doors, conservatories AND bifolds are unlikely to be best at any of them. Bifold-specific specialists know the engineering nuances that catch out generalists — threshold drainage, hinge alignment over time, panel weight calculations.

8. What to ask for in a quote

• System name and manufacturer (e.g. Origin OB-49, Schüco AS-FD75, Reynaers MasterPatio)
• Frame finish (RAL number)
• Glass specification — including U-value, gas fill (argon or krypton), spacer type (warm-edge)
• Threshold type
• Number of panels, opening direction, traffic door yes/no
• Guarantee terms — frame, hardware, glazing separately
• Installation timeline and what happens if delivery delays beyond it
• Removal and disposal of existing doors/frames
• Making-good — internal plastering and external pointing/rendering

9. Realistic timelines

Survey to installation: typically 6–10 weeks. Most of this is manufacturing lead time — the installation itself takes 1–3 days. Don't accept a "we can install next week" promise — quality manufacturers don't have stock; everything is made to order.