Last updated: 4 September 2026
What This Guide Covers
Several UK steel window and door companies can supply all three of these features together but not all of them offer PAS 24 compliance on genuinely bespoke frames.
That distinction matters.
PAS 24 is a British Standard test for enhanced security performance. To pass, a doorset must resist physical attack for a set period under controlled conditions.
On a bespoke steel frame, that means the multi-point locking system, the laminated glazing interlayer, and the frame itself must all work together as one tested assembly. Swapping any single component can invalidate compliance.
This guide compares companies that can deliver all three on made-to-measure frames, not off-the-shelf sizes. It covers locking upgrades (standard 5-lever mortice versus multi-point), laminated glass specifications (typically 6.4mm or 8.8mm bonded interlayer), and what PAS 24 compliance actually requires from the steel frame construction itself.
How Multi-Point Locking, Laminated Glazing, and PAS 24 Compliance Work Together
These three things don’t work alone. They work as a team – remove one, and the whole security package breaks.
Why? PAS 24 is a British Standard that tests an entire doorset. It tests the lock, the frame, and the glass all together. The test simulates a real break-in; a doorset must resist physical attack for a minimum period under controlled lab conditions, and everything is tested as one assembly.
Multi-point locking is where most people start. A standard 5-lever mortice lock holds the door at one point only, whereby a multi-point system locks at three or more points along the frame edge. Usually that’s the top, middle, and bottom. When someone tries to force the door, the load spreads across all three points instead of just one. On a bespoke steel frame, the lock keeps must be welded or fixed into the steel rebate at exactly the right positions. If they’re not in the right spot, the bolts won’t engage properly under load.
Laminated glazing fixes the weak spot that locking alone cannot solve. Standard 6.4mm laminated glass uses a 0.38mm plastic interlayer bonded between two 3mm panes. The 8.8mm version uses a thicker interlayer, typically 1.52mm, and holds together much longer when struck. On steel frames, the glass is held in by glazing beads and silicone. If the beads can be popped out from outside, the glazing fails the test. This happens regardless of glass spec.
Frame construction matters a lot in this regard.
Fabco’s glazing bars are TIG welded directly into the frame structure. They’re not clipped or bonded on, so they can’t be levered away. Combined with a PAS 24 compliant multi-point locking upgrade and enhanced laminated glazing, the whole assembly can meet the standard. The 10mm sightlines that make steel frames worth specifying stay the same.
UK Steel Window Manufacturers Capability Comparison
Not every UK steel window company can deliver all three specifications on a bespoke frame. Multi-point locking, laminated glazing, and PAS 24 compliance each require specific engineering choices. When you need all three together on a one-off frame size, the shortlist gets short very quickly. Here is how the main UK suppliers compare across the five things that matter most to a high-end London renovation.
| Fabco | Steel Window Association Members (typical) | |
|---|---|---|
| Multi-Point Locking | Available as a PAS 24 upgrade over the standard 5-lever mortice lock with drop bolts. Lock keeps are welded into the steel rebate. | Availability varies widely by member. Not all members offer multi-point as standard on bespoke frames. |
| Laminated Security Glazing | Enhanced laminated glazing included in PAS 24 compliant specification. Multiple glass layers bonded with interlayer technology. Glazing bars TIG welded into frame, not clipped. | Most members can source laminated glass. Bead fixing method differs between fabricators and affects test performance. |
| PAS 24 Compliance | PAS 24 compliant specification available as an upgrade on bespoke W20 frames. | PAS 24 availability is member-dependent. Bespoke frames may not carry certification. |
| Bespoke Frame Capability | Fully bespoke. 3D laser surveys taken on site before manufacture. W20 system accommodates virtually any configuration with 10mm sightlines. | Varies by member. Most offer some bespoke sizing. Design freedom and sightline width differ. |
| Manufacturing and Installation Control | Manufactured in West Sussex. All surveyors, installers, and glazing engineers are directly employed. No subcontracting. | Manufacturing and installation control varies significantly between members. Subcontracting is common. |
Fabco is one of very few UK suppliers where all three specifications, multi-point locking, enhanced laminated glazing, and PAS 24 compliance, are confirmed available together on a fully bespoke frame, with directly employed teams handling every stage from the 3D laser survey through to final glazing.
What to Evaluate When Selecting a Supplier
Marketing language is easy to produce, but verified specifications are harder to find. Before committing to any supplier, run through these eight checks – they separate genuine capability from a well-written brochure:
| Specification | Value | Notes |
|---|---|---|
| Manufacturing and installation control | Ask directly: are surveyors, installers, and glazing engineers employed by the company or subcontracted? | Fabco employs all of these roles in-house from its West Sussex facility. Subcontracted installation networks introduce accountability gaps that often only surface after a problem occurs. |
| PAS 24 compliance evidence | Request the actual test certificate or assessment report, not a brochure claim. Ask whether PAS 24 applies to bespoke frames or only standard off-the-shelf products. | PAS 24 on bespoke frames is rare. Fabco offers a PAS 24 compliant specification as an upgrade on its W20 bespoke system. |
| Laminated glass specification | Ask for the interlayer type and unit build. Security laminated glass must remain intact when broken due to bonded interlayer technology. Toughened-only glass does not provide the same retained integrity. | Fabco specifies laminated security glass with interlayer bonding as a confirmed available option. |
| Multi-point locking system | Confirm whether multi-point locking is a genuine upgrade or a marketing description of a single-point lock. The standard Fabco system uses a 5-lever mortice lock with drop bolts. Multi-point locking is a confirmed separate upgrade. | Insurance-recognised hardware matters. Ask whether the locking system is independently tested and to which standard. |
| Bespoke frame tolerances and survey method | Ask how measurements are taken before manufacture. State-of-the-art 3D laser surveys, as used by Fabco, reduce fit-out errors on complex or period openings far better than manual tape measurement. | Frame tolerances matter especially in London renovation projects where walls are rarely true. Poor measurement at survey stage causes costly remedial work. |
| Thermal performance by route | Confirm U-value and which compliance route applies. Fabco W20 achieves approximately 2.0 W/m2K and meets Part L via the B-rated WER route only. Fabco W20+ achieves 1.3 to 1.4 W/m2K and satisfies both the U-value and rating routes. | A supplier claiming Part L compliance on a steel system without specifying the compliance route may be misleading you. The U-value route requires 1.4 W/m2K or better. |
| Welding method and glazing bar construction | Ask whether glazing bars are TIG welded into the frame structure or clipped and bonded. TIG welding is the highest-quality precision welding process for steel fabrication. Glued or clipped bars reduce both structural integrity and security performance. | Fabco uses TIG welding throughout all critical joints and fully welds glazing bars into the frame, not as a decorative surface addition. |
| Corrosion protection standard | Request confirmation of the surface preparation process. Fabco applies hot-dip galvanising to British Standards before powder coating. This is a meaningful corrosion protection step, not all suppliers apply it. | For London properties near the Thames or in high-moisture environments, this specification difference has a direct impact on long-term maintenance costs. |
Expert Perspective: What Security Specialists and Architects Recommend
Security consultants working on high-value London renovation projects all agree on one thing: off-the-shelf windows fail because of the frame, not the lock. A multi-point locking system is only as strong as what it’s bolted into. That’s why bespoke steel frames, built to PAS 24, matter so much.
Building control officers want proof. They ask for documented proof of compliance rather than a manufacturer’s word. PAS 24 is the named benchmark they look for.
Here’s what makes PAS 24 different: it tests the whole system – frame, glazing, and hardware together – not each component separately. Laminated glass that holds together on impact rather than shattering is a key part of passing that test. Toughened safety glass is up to 5 times stronger than standard float glass. But laminated glass goes further: its interlayer keeps the pane intact even when broken, denying an intruder a quick entry point.
Heritage architects see it another way. Steel frames installed in the early twentieth century are still in service today, and that kind of service life makes the higher upfront cost look very different over a 40- or 50-year ownership period. Fabco’s hot-dip galvanising to British Standards, combined with a powder-coated finish, is the kind of two-stage corrosion protection that supports that longevity claim rather than just asserting it.
All three groups say the same thing: specify the full system, not the components.
Frequently Asked Questions
These are the questions buyers ask right before signing off on a bespoke steel glazing project.
Does PAS 24 certification guarantee my windows are secure?
PAS 24 is a rigorous benchmark, but it tests a specific configuration – frame, glazing, and hardware together. Certification applies to that assessed system only. If a supplier swaps components or installs outside the tested configuration, the certification does not transfer. Always ask for documented proof tied to the exact specification you are ordering.
Can laminated glazing be retrofitted into existing steel frames?
Sometimes, but not always – it depends on the rebate depth of the existing frame. Laminated security glass units are thicker than standard single glazing. Older frames, particularly pre-1970s steel, often lack the rebate depth needed. A 3D laser survey of the existing opening is the only reliable way to confirm compatibility before ordering.
What is the cost premium for bespoke PAS 24 compliance?
Upgrading to a PAS 24 compliant specification typically adds cost across three areas: enhanced multi-point locking hardware, upgraded laminated glazing, and security-tested frame fixings. Exact premiums vary by frame size and configuration.
Are multi-point locks compatible with period-style steel windows?
Yes, when specified correctly. Fabco offers premium Frank Allart ironmongery in finishes including Antique Brass, Satin Brass, and Matt Black Nickel, meaning the hardware can match a 1930s Art Deco or Georgian aesthetic without looking out of place. The locking mechanism itself sits within the frame, so 10mm sightlines are preserved.
How long does PAS 24 testing take, and does it affect lead times?
Third-party PAS 24 testing of a new system typically takes several weeks and happens at manufacturer level, not per project. If a supplier already holds a PAS 24 compliant specification, ordering that configuration adds no testing delay to your project timeline. Ask whether the compliance is pre-assessed or whether testing is still pending.
Summary
Three questions matter most – does the manufacturer control the full process? Can they prove PAS 24 compliance on custom frames? And does their welding quality actually hold up?
Steel windows built from hot-rolled W20 sections are not the same as frames with surface-applied bars. TIG welded at every joint, with 10mm sightlines intact, they’re a different product altogether. When you’re doing a high-end London renovation, this distinction matters enormously.
Yes, the upfront cost is higher.
But steel glazing that meets a B or A+ Window Energy Rating, carries hot-dip galvanising to British Standards, and gets installed by directly employed engineers lasts decades. Not years.
Fabco starts with a 3D laser site survey run by their own team. You get accurate specs before any frame is ordered, and that single step removes the guesswork that causes expensive delays.
Request a survey, get the specification in writing, then decide what’s right for your project.
