Fluid Steel Door (External): Slim Steel Doors from 45mm

Frame and leaf together come to a 45mm face width on a 60mm construction depth. On an external door that is a slim steel section — enough that the glass rather than the frame is what you see from across a room, with glazing-led features that preserve those proportions, and with a range of colours and finishes that support the door’s aesthetic appeal; slim enough, too, to sit beside the 20mm window sections without the two looking like different buildings.

Doors are made to 1250mm wide by 2500mm high per leaf at leaf weights up to 150kg, single or double, opening inwards or outwards, with or without fixed side sections or a skylight above. Glass or panel infill runs to 47mm. A double-leaf door therefore covers openings that a single leaf cannot, without moving to a heavier section, and is suitable for both residential and commercial openings.

The system makes doors with segmented or round arches, and curved fixed glazing alongside them. On a Georgian or Victorian entrance the arch is usually the whole character of the opening, and squaring it off is the compromise most replacement schemes end up making. In the right design, steel can preserve the visual character usually associated with timber and complement period details with a slimmer profile. Sheet metal clad leaves are available in the same profile, with or without glass cut-outs, where a solid door is wanted.

Galvanised steel, powder coated or enamelled, is the standard specification, with steel doors treated to prevent corrosion; powder-coated finishes are also highly resistant to UV rays, chipping and flaking, and this service can include colour matching to suit the project. Stainless steel 1.4401 comes bright or polished and is specified in coastal and pool environments where a galvanised finish would suffer. Corten is chosen where a weathered, oxidised exterior is wanted — as at Rusty House, where a Corten facade sets the material language for the whole extension. All three use durable materials, not a coating imitating them. Steel also has lower maintenance requirements than timber and does not warp, crack, swell or splinter with changing weather.

The system is cycle tested to Class 7 under EN 12400 — 500,000 opening cycles, making it a popular choice for a busy property entrance and suitable for high-traffic entrances, and ten times the figure published for the matching steel window. On a front door this is the specification that matters most, because the failure people actually experience is not a break-in but a door that drops, binds or stops closing properly after a few years of daily use.

Water tightness is Class 8A at 450 Pa and air permeability Class 4 at 600 Pa, with sound insulation to 45dB and Class 2 operating forces. This level of acoustic performance is useful where sound reduction matters, including noise-sensitive interior areas and other internal settings. Mechanical strength and impact resistance are both Class 4, under EN 13115 and EN 13049, with shear coupling to EN 14024 and prefabricated barrier glazing to DIN 18008-4. Steel doors are also highly resistant to weather damage, and separate steel fire door specifications can be produced where fire resistance is required, subject to the relevant certified rating and safety standards. The system is CE marked under EN 14351-1.

The system is thermally separated and the published frame value is from 1.9 W/m²K, so insulated steel doors can still deliver good thermal performance when detailed properly, making them suitable for a home or business where more stable indoor temperatures and lower energy bills matter. Steel conducts more readily than aluminium, and a steel door will not match a thermally broken aluminium one on thermal performance, though steel insulated doors can still improve efficiency in various environments — anyone quoting you a figure under 1 is quoting the glass, not the door. Where steel is specified, it is because the section or the material is required. If thermal performance is the priority, the Fluid Timeless Door gives a comparable visual language in aluminium at roughly a third of the cost.

Slim 3D screw-on hinges in stainless steel allow adjustment in three planes after installation, which matters on a heavy door in a period opening that has moved. The striking plate adjusts through four settings and compensates up to 3mm of offset, so a door that drifts can be reset rather than reworked. Locking is by mortise lock with or without top locking, multipoint lock, or electric strike, with hardware upgrades such as digital locks available where the specification calls for them on a security door. Thresholds include a barrier-free variant for level access. Custom hardware, panel options, and weather and draught-proof seals can also be specified to suit the opening and other specific requirements. On selected steel door sets, additional security features can include anti-jemmy studs.

The door and the window are compatible systems sharing a 60mm construction depth and the same three materials, so a whole elevation reads as one range. Their test data is not identical and should never be copied between them: the window is Class 9A for water and Class 4 for durability with an RC2 security rating; the door is 8A and Class 7 with no published security rating. Where security certification is required, steel doors are typically specified against recognized forced-entry standards such as PAS24; this is how security steel doors are often tested and how a product may be secured and certified when the published status confirms it. Each is specified from its own datasheet.

An EPD is published for the system, giving verified environmental data for whole-life carbon assessment, and BIM models are available for the full profile range. On schemes chasing BREEAM or LEED credits both are usually requested at specification stage, and it is often the point at which an unverified product is substituted out.

Steel work on a period building is survey-led — openings are rarely square and rarely consistent between bays, and an arched opening never is. We survey, supply and install, so the measurements that set the sizes and the team that fits them are the same. For advice on options and pricing, contact our friendly team today. See the Fluid Steel Door at Chevening and Dulwich Curves, or see one at our Watford showroom.

Architects — for listed buildings and heritage schemes where a steel section is required and the profile will be inspected, and for arched or curved openings. Request section details, BIM models, the EPD and test certification.

Homeowners — for a front or garden door where the building’s character depends on an authentic steel profile, including arched openings.

Developers — for schemes needing one material palette across doors and windows, with an EPD and BIM models available for environmental assessment and coordination.