Aluminium is the material of choice for folding doors because it is strong enough to carry big glass on slim frames. But 'aluminium bifold' covers everything from budget imports to engineered systems, so knowing what to check protects you when quotes vary wildly.
Configuration first
Decide how many leaves and which way they fold before you talk price. A common Hertfordshire layout is a three- or four-leaf set with a single traffic leaf for everyday use, so you are not folding the whole wall to let the dog out. Get the swing and stack direction drawn on a plan. Our Schüco bifold explainer shows how the leaf count changes the look.
- Frame material
- thermally broken aluminium
- Glazing
- double or triple sealed unit
- Finish
- polyester powder coat, any RAL
- Security
- PAS 24 recommended
- Warranty
- check both frame and paint
Glazing and thermal numbers
The glass does most of the thermal work. Ask for the whole-door Uw, not just the centre-pane glass figure, so you are comparing like for like. If overheating on a south elevation worries you, solar-control glass is worth the small uplift — see solar control glazing and the wider picture in U-values explained.
Finishes that last
Anthracite grey (RAL 7016) remains the runaway favourite, but a quality polyester powder coat will hold any colour for years. Dual-colour — a darker outside, neutral inside — is popular and usually a modest extra. Matt finishes hide handling marks better than gloss.
Comparing quotes fairly
Cheap bifolds and engineered ones can look identical in a photo. Line up the glass spec, the security rating, the threshold type and the installer's warranty before you judge on price. For a trusted local reference point, folding door specialists in Hertfordshire will quote against a proper drawing, and it is always worth reading how to choose a bifold supplier first.