The short answer
Each additional bifold leaf typically adds roughly £700–£1,000 to the total, so a 4-door set costs meaningfully more than a 3-door. In uPVC, a 3-door set commonly runs £1,950–£2,800, with a 4-door set stepping up toward the £2,800–£3,500 bracket. In aluminium, a 3-door set typically falls in the £3,500–£7,000 range and a 4- or 5-door set runs higher again, with a 5-door aluminium system reaching roughly £5,260–£7,500. Beyond the leaf count, the wider opening a larger set needs may bring in a bigger lintel and more structural work, and the split configuration (for example 3+0 versus 2+1) affects how the doors stack. The price difference is real, but it buys both a wider opening and more glass.
Going from three leaves to four is not just one more panel — it usually means a wider opening too, which can pull in extra structural work. Here is how the brackets and the extras compare.
Typical UK costs
- Each extra leaf+£700–£1,000
- 3-door uPVC£1,950–£2,800
- 4-door uPVC~£2,800–£3,500
- 3-door aluminium£3,500–£7,000
- 5-door aluminium~£5,260–£7,500
What an extra leaf adds
The simplest way to read the difference is per leaf: each additional door adds roughly £700–£1,000 in materials and fitting. So a 4-door set is broadly a 3-door plus one leaf — but the bigger factor is often the wider opening a four-leaf set needs. A wider span can require a larger structural lintel and more opening-up work, which adds beyond the door cost itself. Configuration matters too: a 3+1 or 2+2 split changes where the doors stack and which way the traffic door opens, so it is worth deciding the layout before pricing.
| Set | uPVC | Aluminium |
|---|---|---|
| 3-door | £1,950–£2,800 | £3,500–£7,000 |
| 4-door | ~£2,800–£3,500 | higher than 3-door |
| 5-door | £3,560–£4,240 | ~£5,260–£7,500 |
| Each extra leaf | +£700–£1,000 | +£700–£1,000 |
Indicative UK figures for guidance; aluminium varies widely by quality and span. Sources: ExpertSure and MyJobQuote bifold cost guides.
Why width matters as much as leaf count
A four-leaf set almost always means a wider opening than a three-leaf, and that is where hidden cost can appear. If the new aperture is wider than the old one, you need a structural lintel sized for the span (commonly £500–£1,500 for the lintel) plus the building-regs work that goes with opening up a wall. Two quotes for a 3-door and a 4-door can therefore differ by more than the price of one extra leaf, because the larger set carries more structural work. Settle the opening width and configuration first, then price both options on the same scope.
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We'll match you with a FENSA-registered door installer who measures your opening and quotes the 3-door and 4-door layouts, with material, glazing and any structural work set out clearly.
Frequently asked questions
How much more is a 4-door bifold than a 3-door?
Each extra leaf typically adds roughly £700–£1,000, so a 4-door uPVC set steps up toward £2,800–£3,500 from a £1,950–£2,800 3-door. A 4-door aluminium set runs higher than its 3-door, partly because of the wider opening it needs.
Why does a 4-door set cost more than just one extra panel?
Because a four-leaf set usually means a wider opening, which can require a larger structural lintel and more opening-up work. That structural cost is on top of the price of the extra leaf.
Does the door configuration affect the price?
The split — such as 3+0, 2+1 or 2+2 — affects how the doors stack and which is the traffic door, and a wider configuration may need more structural support, but the leaf count and material are the main price drivers.
Sources & further reading
- ExpertSure — bifold doors cost by material and panel count
- MyJobQuote — bifold door installation cost guide
Figures on this page are typical UK ranges drawn from published sources and depend on your specific opening and material. They are guidance, not a quotation.