The Schüco AS FD 75 is the door most UK homeowners actually mean when they say "Schüco bifold." It's the flagship folding-door system in the residential range, and after several years on the market it has become the reference against which other aluminium bifolds are judged. This guide walks through what the system does, where the 75mm number comes from, and how it holds up on real openings in and around St Albans.
What the "75" refers to
Schüco's residential systems are numbered by the depth of the frame profile in millimetres. AS FD 75 uses a 75mm-deep aluminium profile with a polyamide thermal break separating the outer and inner faces. In practical terms, that gives you enough material to accommodate double or triple glazing, run the multi-point locking gear, and hit thermal performance figures that clear current Building Regulations comfortably.
For context, the shallower AS FD 60 exists in Schüco's commercial range but has largely been superseded for UK residential work — the 75mm depth is the residential standard now.
Sightlines and configurations
The single number that tends to matter to homeowners is the sightline — the visible width of aluminium where two panels meet. On the AS FD 75, the mid-rail interlock sits at around 124mm across the meeting stiles. That's slim without being fragile-looking, and it's the honest answer: if a supplier claims dramatically slimmer sightlines on a folding door, they're either measuring differently or they're specifying a different system.
Standard panel configurations range from two-panel through to seven-panel arrangements. Common residential builds we see across Hertfordshire are:
- 3-panel (2+1) for openings around 3.0m — traffic-door on the right, two folding left.
- 4-panel (3+1) for openings up to ~4.0m — the sweet spot for a typical rear extension.
- 5-panel (4+1) up to ~5.0m — noticeably more folded stack width, plan for it.
- 6- and 7-panel for larger openings — usually split (3+3 or 4+3) with a French-style meeting stile in the middle.
Thermal performance
With triple glazing and warm-edge spacers, the AS FD 75 achieves overall U-values down to around 1.3 W/m²K. With standard double glazing it sits at approximately 1.6 W/m²K. Both are well inside current Approved Document L limits for replacement doors (which set 1.4 W/m²K as the trigger for new build and slightly higher for replacement work).
For an extension you're heating year-round, our editorial view is that upgrading from the base double-glazed spec to a warm-edge triple pays back sensibly on a payback horizon that fits most homeowners' plans.
Security ratings
The AS FD 75 is available with PAS 24 : 2016 certification and can be built to Secured by Design spec. That involves reinforced hinges, laminated inner glass, and the concealed multi-point espagnolette lock the system is known for. If you're specifying a bifold on the ground floor, insist on PAS 24 as a baseline — some cheaper folding systems on the UK market are not tested to that standard.
Threshold options
Three thresholds are commonly used:
- Standard weathered threshold — best weather performance, ~65mm upstand.
- Low threshold — around 25mm, a workable compromise.
- Flush/rebated threshold — level with the finished internal floor, requires careful detailing of drainage outside.
The flush option is what most architects specify, but it depends on there being a properly designed drainage channel and a covered overhang above. Rushed flush thresholds are the single most common cause of bifold water-ingress complaints — see our installation guide for the detail.
Sourcing an AS FD 75 near St Albans
Schüco does not sell direct to homeowners. The system reaches you through authorised fabricator-installers who cut, weld and glaze the frames locally. In our editorial coverage of the Hertfordshire market, 5EC Aluminium is one of the fabricators consistently supplying and fitting the AS FD 75 across St Albans and the surrounding area — their folding door page details the system depths and typical configurations they carry.
For manufacturer-level product data, Schüco's UK site publishes the full technical dossier, including U-value tables and Declaration of Performance documents.
Editorial verdict
The AS FD 75 is not the cheapest folding door on the market, and it isn't trying to be. What it delivers is a properly engineered system with predictable performance, workable panel weights, and a serviceable hardware set that authorised fabricators can support long-term. For a rear extension or a garden-facing kitchen in a St Albans property, it remains the folding door we'd specify by default.