Last updated: 4 September 2026
Introduction: Why Selection Criteria Matter
When interior designers need custom steel windows, doors, and room dividers made just right, they call the same names again and again. Fabco is amongst the top of the list. A few other British shops make the cut too, and these firms build to tight measurements and perfect finishes.
Fabco stands out in one particular way. Each project gets its own engineer assigned to it, and before anything is built, the team uses 3D laser surveys to check measurements. Then comes a five-step process to deliver the finished work.
Why pick the right fabricator? It matters more than you’d think.
Get it wrong and problems can pile up fast; A powder-coated RAL colour comes back mismatched, or sightlines specified at 10mm arrive at 14mm. Sign-off meetings stall because no single point of contact owns the decision.
For high-end interiors, those failures cost real money. The solution is simple – evaluate fabricators against the same measures every time and check and double-check for accuracy, for welding standard, and for delivery structure. All of which helps to prevent unwelcome surprises.
Step 1: Define Your Project Requirements
Write down your answers to these five questions before you call anyone. They decide everything else.
What is your aesthetic intent? Steel sightlines aren’t all the same. Fabco’s W20 system sits at 10mm, some competitors offer wider sightlines. That difference changes how a room reads.
What thermal targets must you hit? External glazing in new builds must meet Building Regulations Part L. Fabco’s W20 achieves approximately 2.0 W/m²K and a B Window Energy Rating, meeting Part L for replacement windows via the WER/DSER rating route only. Our W20+ variant reaches 1.3-1.4 W/m²K, rated A+. Know which route your project needs before the conversation starts.
Do any doors need fire rating? FD30 certification requires a specific steel profile, the W40, and changes fabrication complexity significantly.
What’s your timeline? Bespoke steel lead times vary by fabricator. Ask each one early on to avoid disappointment.
How complex are your internal partitions? Fixed screens, sliding doors, and room dividers each carry different structural requirements. List every configuration type before reaching out.
Get these answers on paper first. You’ll ask better questions and spot weak answers faster.
Step 2: Evaluate Fabricator Capabilities Against Your Criteria
Once you know what your project needs, you can measure fabricators against it. The six criteria below are what separate reliable steel specialists from suppliers who look good on paper but struggle under real project conditions. Use this table to score each fabricator you speak to.
| What strong looks like | What to avoid | |
|---|---|---|
| Manufacturing control | Full in-house fabrication, surveying, installation, and glazing by directly employed teams. Fabco manufactures in West Sussex with no subcontracted delivery stages. | Subcontracted installation or glazing teams. No single point of accountability across the five key delivery stages. |
| Design sign-off process | Dedicated project engineer per job. State-of-the-art 3D laser surveys used before production begins. Written sign-off at each stage. | No named project contact. Measurements taken by a third party. No formal review milestone before fabrication starts. |
| Thermal performance (verified) | Stated U-values backed by a recognised rating route. Fabco W20 achieves approximately 2.0 W/m2K, B-rated. Fabco W20+ achieves 1.3 to 1.4 W/m2K, A+-rated, exceeding Building Regulations Part L. | Unverified or approximate U-values. No Window Energy Rating or Doorset Energy Rating on record. Claims made without a named compliance route. |
| Welding standard | TIG welding throughout all critical joints. Glazing bars fully welded into the frame structure, not clipped, glued, or surface-applied. Minimal weld distortion. | MIG welding or bonded glazing bars. No stated welding specification. Decorative bars that are not structural. |
| Fire rating capability | FD30 fire-rated doors and screens using W40 steel profile. Independently assessed by Warringtonfire. | No independent fire assessment on record. Fire rating claimed without a named test house or report number. FD30 applied to W20 profiles, which is outside assessed scope. |
| Finish accuracy and sightlines | 10mm sightlines on W20 and W20+ systems. RAL colour-matched, UV-resistant silicone throughout. Hot-dip galvanising to British Standards before powder coat. Frank Allart ironmongery available in five finishes. | Sightlines wider than 15mm. Generic silicone not colour-matched. No stated surface preparation standard before finishing. |
Any fabricator who cannot give you a named project engineer, a verified U-value rating, and a stated welding process before the contract is signed is carrying risks your project cannot afford. The specifics in this table are the questions worth asking.
Step 3: Validate Quality, Finish Accuracy, and Collaborative Processes
Comparing brand listings is only the start; real validation means checking what a fabricator can prove before a contract is signed. These five touchpoints separate fabricators who can document their quality from those who only describe it.
| Specification | Value | Notes |
|---|---|---|
| Site audit of completed projects | Request access to at least two finished installations of similar scope, ideally within the past 18 months. | Look specifically at sightline consistency, silicone finish, and ironmongery alignment. On Fabco projects, the 10mm sightline on W20 and W20+ systems should be uniform across every frame. Inconsistency here points to poor in-house quality control. |
| Finish sample review | Request a physical powder-coat sample in your specified RAL colour alongside the silicone used at glazing stage. | Fabco uses RAL colour-matched, UV-resistant silicone throughout wet glazing. A fabricator who cannot supply a matched silicone sample alongside the frame finish carries a visible finish risk on every joint. |
| Design sign-off documentation | Ask for a copy of the fabricator’s standard sign-off pack, including drawing approval stages and named project engineer details. | Fabco assigns a dedicated project engineer per project as a single accountability point across survey, manufacturing, and installation. If no named individual is confirmed before contract, escalation routes are unclear. |
| Thermal performance certificate | Request the Window Energy Rating or Doorset Energy Rating certificate, not just a quoted U-value figure. | Fabco W20 holds a B-rated WER with a whole-window U-value of approximately 2.0 W/m2K. Fabco W20+ holds an A+ rating with a U-value of 1.3 to 1.4 W/m2K. A fabricator who quotes a U-value without a named rating route or certificate cannot confirm Part L compliance. |
| Case studies matched to project type | Request at least one documented case study matching your project category: heritage, contemporary extension, commercial, or internal partition. | Fabco’s W40 system carries an independently assessed FD30 fire rating from Warringtonfire. If your brief includes fire-rated internal screens, verify the fabricator’s assessment covers doors and screens, not doorsets only. |
Trusted UK Fabricators: Quality & Design Collaboration Profiles
Steel fabricators are not interchangeable. The differences that matter most to designers – finish accuracy, drawing approval stages, named accountability – only show up when you compare them side by side.
Fabco
Manufacturing base: West Sussex, UK
Systems available: W20, W20+, W40 (FD30 fire-rated doors and screens)
Sightlines: 10mm (W20 and W20+)
Thermal range: 2.0 W/m²K (W20, B-rated WER) to 1.3-1.4 W/m²K (W20+, A+-rated WER)
Fire rating: FD30, independently assessed by Warringtonfire, covering doors and screens
Design collaboration model: Dedicated project engineer per project; 3D laser survey before production; drawing approval stage included; RAL colour-matched silicone standard across all wet glazing
Security: PAS 24 compliant specification available as upgrade; standard 5-lever mortice lock with drop bolts
Heritage fit: Strong. The W20 works well in listed buildings, conservation areas, and period properties. Single glazing is accepted where planning requires it.
Contemporary fit: Strong. W20+ beats Part L on both U-value and rating routes. It looks identical to W20 from the outside.
Internal partitions: W20 screens and room dividers are available. W40 handles fire-rated internal screens when FD30 compartmentation is needed.
Best for: Designers who want one named contact, proper fire-rating paperwork, and a fabricator that makes and installs everything itself – no subcontracted networks.
Limitation to note: Premium price point. You’ll spend more upfront than some mid-market suppliers. The lifecycle cost argument is strong, though, given steel lasts for decades.
For fabricators beyond Fabco, apply the checklist from Section 4: request WER certificates, matched silicone samples, and documented sign-off packs before shortlisting.
Frequently Asked Questions: Selection and Collaboration
These are the questions designers ask most when shortlisting steel fabricators. Short answers, real numbers.
How do I know if a fabricator has a rigorous design sign-off process?
Ask for a sample sign-off pack from a previous project. A serious fabricator will show you drawing approvals, material selections, and a named engineer assigned to the project. Fabco uses state-of-the-art 3D laser surveys before production starts, with a dedicated project engineer as a single point of contact throughout.
Does in-house manufacturing actually guarantee better quality?
Not automatically, but it removes the risk of quality breaking down between suppliers. Fabco employs its own surveyors, installers, and glazing engineers rather than subcontractors, meaning quality control runs continuously across all five stages of delivery.
How do I verify thermal performance claims?
Ask for the Window Energy Rating certificate. Fabco’s W20 holds a B rating at 2.0 W/m²K. The W20+ achieves an A+ rating at 1.3 to 1.4 W/m²K, exceeding Part L on both the U-value and rating routes.
Are steel fabricator lead times predictable?
UK-based manufacturers generally offer better scheduling control than imported systems. Because Fabco manufactures in West Sussex with directly employed teams, project coordination stays within one organisation rather than across multiple suppliers.
Is bespoke steel worth the higher upfront cost?
Steel windows installed in the early twentieth century are still in service today. The higher initial investment spreads across decades of service life. Fabco’s powder-coated finish with UV-resistant, RAL colour-matched silicone also reduces maintenance costs over that period.
Which steel system do I specify for a fire-rated internal partition?
You need the W40 profile, not the W20. Fabco’s W40 FD30 system is assessed by Warringtonfire for up to 30 minutes integrity-only fire resistance on doors and screens.
Summary
Brand reputation is just the start. Real protection comes from checking three specific areas: fabrication quality, thermal credentials, and delivery accountability. These checks keep design sign-off consistent throughout a project.
Look at welding method and sightlines. Fabco’s W20 holds 10mm. Check energy ratings using certificates, not just what companies say. The W20+ achieves A+ at 1.3-1.4 W/m²K. Ask about installation teams – are they directly employed or subcontracted?
Those three checks matter most. Apply them consistently to every fabricator: that’s how you find the reliable ones from the ones that only look good on paper.
