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Bi-Fold Door Calculator
Calculate bi-fold door panel configurations, costs and U-values for aluminium, uPVC, timber and composite frames with UK Part L compliance.
Structural opening width
Standard 2100mm
Indicative £/m² — override the default (0 = auto)
Fitting labour
From the product datasheet (0 = use typical estimate)
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How We Calculate This
This calculator estimates bi-fold door costs based on opening size, frame material, panel count and glazing.
The formula
Total = (Area × Base Rate × Glazing Multiplier) + Installation
- Base rates vary by frame material
- Triple glazing adds ~30% to supply cost
- Panel width = Opening width ÷ Number of panels
- Weight = Area × kg/m² × Glazing factor
A note on the figures
The default supply rates (aluminium ~£950/m², uPVC ~£650, timber ~£850, composite ~£1,200), the weight rates and the typical U-values are indicative 2026 ballpark estimates — actual prices and thermal performance vary widely by system, brand and specification. Enter your own £/m² and the whole-door U-value from the manufacturer datasheet (Advanced Options) for an accurate figure. The 1.4 W/m²K Part L check follows Approved Document L 2021 (Vol 1, Table 4.2) for replacement glazed doors. If you are comparing systems, our UK sliding door cost calculator prices inline, lift & slide and pocket sliding doors on the same supply-plus-installation basis.
Frequently Asked Questions
Under Approved Document L 2021 (Volume 1, Table 4.2), replacement glazed doors must achieve a whole-door U-value of 1.4 W/m²K or better (or Doorset Energy Rating band C). For new builds the notional specification is 1.2 W/m²K. Whole-door figures vary widely by system: double-glazed thermally-broken aluminium bi-folds commonly run 1.6-2.0 W/m²K, so not every double-glazed door passes — some slim premium systems reach 1.4. Triple glazing typically achieves 0.8-1.2 W/m²K and comfortably meets the limit. Always confirm the U-value from the manufacturer datasheet.
Bi-fold leaves typically run 600-1200mm wide, with around 1000-1200mm the practical maximum (limited by sash weight — residential hardware is usually rated to 80-100kg per leaf, commercial up to ~120kg). For a 3m opening, 3-4 panels work well; for 4-5m, 5-6 panels. Odd numbers allow a traffic door. Going much above 1200mm per leaf risks excessive weight and faster track and roller wear.
Yes. Bi-fold doors require compliance for thermal performance (Part L), structural opening (Part A), and accessibility (Part M). Installation must be by a FENSA-registered installer or you need a building control certificate.
Aluminium is most popular due to slim sightlines, strength and low maintenance. uPVC is cheapest but has thicker frames. Timber offers traditional appearance but needs maintenance. Composite combines both at premium cost.
A typical aluminium bi-fold panel weighs 30-45 kg/m². A 3m x 2.1m 3-panel set weighs approximately 200-270 kg total. Triple glazing adds about 30% more weight. Track and rollers must be rated for the total weight.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.