Last updated: 12 August 2026
UK manufacturers have carved out distinct niches in heritage-style steel windows and doors. Fabco and a select group of specialist fabricators each serve different market segments and aesthetic philosophies.
Fabco manufactures in West Sussex. The company positions itself at the premium end with 10mm sightlines, TIG-welded construction, and thermal ratings spanning from B (W20, ~2.0 W/m²K) to A+ (W20+, 1.3–1.4 W/m²K).
Here’s where most project teams hit a wall: somewhere between mood boards and manufacturer briefs, they’ve nailed the look. Warehouse glazing. Agrarian iron frames. Forge-black casements. But the technical reality (which profile system fits? What glazing spec? Which compliance route?) remains fuzzy.
This guide bridges that gap.
It moves from aesthetic intent to a solid vendor brief in eight structured steps, tackling profiles, thermal ratings, Part L compliance routes, and security standards like PAS 24.
Step 1: Define Your Heritage Aesthetic Vision
Before contacting any manufacturer, a project team needs a clear brief that translates aesthetic intent into technical language. Industrial and agricultural heritage aesthetics cover a wide range, from Victorian glasshouse glazing bars at 25mm centres to inter-war factory casements with 40mm face widths. Without specifics, manufacturers can’t quote accurately, and briefs get misread. Work through this checklist before picking up the phone.
| Specification | Value | Notes |
|---|---|---|
| Historical Reference Period | Identify the decade or era your aesthetic targets, e.g. 1890–1910 glasshouse, 1920s–1940s factory, 1950s agricultural barn | Different eras have distinct glazing bar spacings, opening configurations, and ironmongery styles. A 1930s forge aesthetic typically means wider panes, minimal subdivision, and black finish; very different from Victorian lean-to glazing with frequent bars at roughly 150mm centres. |
| Sightline Width Target | Specify in millimetres – heritage steel typically ranges from 10mm to 45mm face width depending on era and profile | Fabco’s W20 system achieves 10mm sightlines with a 32mm face width. Wider profiles read as more industrial and heavier. Confirming this number upfront stops manufacturers defaulting to their standard system when your brief needs something different. |
| Colour Reference | Provide a specific RAL code, not a word like ‘black’ – RAL 9005 Jet Black and RAL 9011 Graphite Black look very different at scale | Agricultural and industrial heritage projects most commonly specify RAL 9005, RAL 7016 Anthracite Grey, or heritage dark greens such as RAL 6009. Fabco offers bespoke RAL powder-coat finishes, so a precise code eliminates ambiguity at quotation stage. |
| Opening Configuration | List each opening type required: fixed lights, side-hung casements, top-hung vents, or French doors, with approximate quantity and size in millimetres | Industrial heritage projects often favour large fixed glazed panels with occasional top-hung vents, mimicking factory clerestory windows. Mixing fixed and opening lights in the brief allows manufacturers to price accurately from the start. |
| Glazing Bar Layout | Describe the pattern (horizontal only, grid, no bars) and note approximate pane dimensions in millimetres | Agrarian and forge aesthetics often use a simple two-pane vertical split or no bars at all, letting large glass panels dominate. Victorian glasshouse references need a denser grid. Fabco’s W20 glazing bars are fully TIG-welded into the frame structure, not clipped on, so the layout becomes a structural decision, not just a visual one. |
| Ironmongery Style Reference | Specify finish and handle type: e.g. Matt Black Nickel, Antique Brass, or plain bar handle; and note if heritage ironmongery catalogues apply | Fabco offers Frank Allart ironmongery in six finishes including Matt Black Nickel and Satin Brass. For agricultural heritage projects, Matt Black Nickel typically reads most authentically. Naming the finish prevents a premium frame arriving with mismatched hardware. |
Step 2: Specify Technical & Material Requirements
When writing a material specification for an industrial or agricultural heritage project, vague language causes problems. Terms like ‘steel windows in black’ leave too much open to interpretation. Use the language below to lock down exactly what gets made and installed.
| Specification | Example | Notes |
|---|---|---|
| Steel Profile System | Hot-rolled W20 section, 32mm face width, 10mm sightline | W20 is the industry-standard profile for heritage and industrial steel glazing. Specifying hot-rolled rather than cold-formed is important: hot-rolled sections have the authentic visual weight and proportions associated with early twentieth-century factory and agricultural buildings. |
| Surface Finish | Durable powder coat, RAL 9005 Jet Black or RAL 7016 Anthracite Grey | Bare or patinated steel is not a practical external finish. Powder coat is the correct industrial choice. Avoid gloss levels above satin for agricultural contexts. Fabco uses durable powder-coat systems over hot-dip galvanising to British Standards, which gives corrosion resistance underneath the colour coat. |
| Weld Specification | TIG welded joints throughout, glazing bars fully welded into frame structure | TIG welding produces clean, strong joints with minimal distortion. Specifying it by name rules out clipped or bonded glazing bars, which look decorative rather than structural and do not replicate the authentic steel aesthetic of original industrial frames. |
| Glazing Unit | 18mm slimline double glazing: 4mm outer pane, 10mm krypton-filled cavity, 4mm inner pane | This unit fits within the W20 profile while achieving a U-value of approximately 2.0 W/m2K, meeting Building Regulations Part L via the B-rated WER route. With the W20+ profile it achieves 1.3-1.4 / A+ …Specifying krypton fill rather than argon is worth noting in the brief, as it improves thermal performance within the same slim cavity depth. |
| Fixing Hardware | Non-rusting stainless steel fixings throughout | Specify stainless steel fixings explicitly. Standard mild steel fixings corrode faster than the frame itself and cause staining. For agricultural environments, ask whether enhanced marine-grade protection is available for any exposed metalwork. |
| Corrosion Protection | Hot-dip galvanising to British Standards applied before powder coat | This two-layer system is the correct specification language for external steel in exposed agricultural or industrial settings. Hot-dip galvanising alone is a recognised British Standard process, so referencing it by name gives a manufacturer a clear, checkable requirement. |
Step 3: Heritage Steel Specification Comparison
Not all steel profiles look the same on a building. Hot-rolled steel, the traditional choice for industrial and agricultural glazing, produces genuinely slim sightlines because the material is shaped under heat, giving it high strength without bulk. Cold-formed (or pressed) steel is bent from flat sheet and tends to produce wider, boxier frames. For heritage projects where replicating the original factory or barn aesthetic matters, profile type is one of the most important decisions a specifier makes. Fabco’s W20 system uses hot-rolled sections with 10mm sightlines and a 32mm face width, sitting at the authentic end of the spectrum.
| Profile Type | Typical Sightline | Industrial Heritage Aesthetic Effect | |
|---|---|---|---|
| Hot-rolled steel (e.g. Fabco W20) | Hot-rolled steel | 10mm sightline, 32mm face width | Closest match to original 1920s-1950s factory and agricultural glazing; slim, graphic, authentically industrial |
| Cold-formed steel | Cold-formed / pressed steel | Typically 20-35mm sightline | Broader frames; suits utility or budget conversions but reads as modern rather than heritage |
| Aluminium slimline | Extruded aluminium | Typically 18-25mm sightline | Lighter appearance; lacks the material weight and shadow-line depth associated with original steel frames |
| Timber with steel appearance | Painted softwood or hardwood | Typically 44-68mm face width | No authentic steel aesthetic; often used where budget limits steel but heritage character suffers noticeably |
For agricultural and industrial heritage projects, hot-rolled steel with sightlines at or below 15mm is the only profile type that genuinely replicates the original glazing aesthetic; anything wider reads as a modern substitute.
Not every steel window maker genuinely understands industrial heritage aesthetics. These questions reveal whether a manufacturer can actually deliver.
Ask every shortlisted manufacturer these questions:
- “What profile system do you use – hot-rolled or cold-formed?” Hot-rolled steel produces the authentic sub-15mm sightlines that match original factory glazing. Cold-formed sections typically run 20–35mm wide and read as modern.
- “What sightline width does your standard system achieve?” Anything above 15mm struggles to replicate pre-1960s agricultural or industrial windows. Fabco’s W20 system achieves 10mm sightlines with a 32mm face width.
- “How are glazing bars attached – welded or applied?” Genuinely structural bars are TIG welded into the frame. Glued or clipped bars are decorative and visually unconvincing up close.
- “Can you supply hot-dip galvanised protection to British Standards?” This is measurable corrosion protection, not just a paint finish.
- “Do you manufacture in the UK, and do you employ your own installation teams?” Both affect programme control and accountability on complex heritage sites.
Strong answers are specific. Vague ones are a warning sign.
Step 4: Review Samples & Approve Finishes – FAQs on Heritage Steel Specification
Once samples arrive on site, approving them correctly saves costly rework later. These are the questions heritage specifiers ask most often at this stage.
How long does powder coating take to fully cure before I can assess the colour accurately?
Powder-coated steel is typically touch-dry within minutes of the oven cycle, but allow 24 hours before comparing against RAL reference charts under natural daylight. Assess colour at midday rather than under artificial lighting, which shifts warm tones significantly.
Which RAL colours are considered heritage-appropriate for agricultural and industrial steel glazing?
Original factory and agricultural glazing was almost universally finished in black or very dark grey. RAL 9005 (jet black) and RAL 7016 (anthracite grey) are the most widely accepted by conservation officers. Fabco offers bespoke RAL colours, so specifiers can match surviving original paintwork using a spectrophotometer reading.
How do I confirm glazing bars are genuinely structural rather than decorative?
Ask the manufacturer for a fabrication drawing confirming TIG welding of bars into the frame structure. Fabco fully welds all glazing bars into the W20 frame rather than clipping or bonding them, which is verifiable on the physical sample by running a fingernail along the junction – bonded bars show a sealant line.
What maintenance schedule should I expect for powder-coated heritage steel windows?
A well-applied powder coat on hot-dip galvanised steel to British Standards requires inspection every 5 to 10 years, with localised touch-up only if chipping occurs. This is significantly less demanding than the annual painting cycles associated with original pre-1960s factory glazing.
Do conservation officers require physical samples or will digital renders suffice for approval?
Conservation officers commonly ask for a physical powder-coated sample and a glazed section – slim sightlines like the 10mm W20 profile are difficult to appreciate without one. Digital renders are accepted as supporting material only. Slim sightlines like Fabco’s 10mm W20 profile are difficult to appreciate without a tangible sample.
Fabco operates from West Sussex and makes bespoke steel windows and doors. They use hot-rolled W20 sections with 10mm sightlines, some of the narrowest widely available in the UK market. Their W20 system works well for barn conversions, mill buildings, and listed industrial structures. All glazing bars are TIG-welded into the frame (not clipped), and every project uses directly employed surveyors and installers rather than subcontractors. The company appeared on Grand Designs and has over two decades of British production behind it.
Summary
Getting heritage steel glazing right means keeping control at every stage. Loose specification, subcontracted surveys, or generic manufacturing can each quietly dilute the authenticity a project demands.
Fabco’s model addresses this directly.
With 10mm sightlines, TIG-welded glazing bars, and a five-step delivery process run entirely by directly employed surveyors, engineers, and glaziers, the design intent doesn’t get lost between West Sussex and site. The W20 system meets Building Regulations Part L via a B-rated WER, while the W20+ hits a U-value of 1.3–1.4 W/m²K – both without sacrificing the slim steel profile that makes industrial heritage projects work.
