Specifying Steel Doors: An Updated Guide for Architects in 2026

Why Steel Door Specification Demands Precision

Specifying an entrance door appears straightforward until you consider the number of performance requirements converging on a single building element. Security, thermal efficiency, fire resistance, acoustic performance, durability, aesthetics and accessibility must all be addressed within a specification that is buildable, verifiable and compliant. For steel entrance doors, the specification process carries additional considerations around weight, structural interface and finish durability that differ materially from timber or composite alternatives.

This guide provides architects with a current, practical framework for specifying steel doors in 2026, covering performance standards, structural detailing, hardware selection and the manufacturer engagement process.

NBS Specification Clauses

The NBS system remains the standard specification platform for UK construction projects. Steel entrance doorsets fall primarily under section 32-20 (External Doorsets) within NBS Create and NBS Chorus. When drafting clauses for a bespoke steel entrance door, the specification should address the following as a minimum:

Doorset type — single leaf, double leaf, with or without sidelights and fanlights
Security classification — PAS 24:2022 as baseline, LPS 1175 SR2 or SR3 where enhanced security is required
Thermal performance — target U-value, referencing Approved Document L
Fire resistance — FD30 or FD60 where required by Part B or the Fire Safety Act
Acoustic performance — weighted sound reduction index (Rw) where relevant
Finish specification — RAL colour, application method, coating thickness
Hardware schedule — locking mechanism, handle, knocker, letter plate, numerals, closer, threshold
Glazing specification — if applicable, glass type, thermal and security ratings

Each clause should reference the relevant British or European standard and specify the required level of independent certification. Avoid generic phrases such as "to approved detail" — these create ambiguity that inevitably leads to site disputes. Learn more about our process for working with architectural practices.

Performance Requirements

Security

The regulatory baseline for entrance door security in England and Wales is PAS 24:2022, mandated by Approved Document Q. This applies to all new dwellings and conversions creating new dwellings. For refurbishment projects, PAS 24 is recommended but not always mandated — though specifying below this standard is difficult to justify professionally.

Beyond PAS 24, the Loss Prevention Certification Board's LPS 1175 standard provides graded security ratings. SR3 is the highest rating routinely specified for residential applications, resisting sustained attack with professional tools over an extended period. For high-value residential projects across London, Manchester and Birmingham, SR3 is increasingly the default specification rather than an enhancement.

Secured by Design accreditation confirms that the doorset meets police-approved security standards. It is a valuable specification line for projects where end-user insurance requirements or planning conditions reference crime prevention. Our security specification provides the full technical detail architects need for their documentation.

Thermal Performance

Approved Document L (2021 edition, with 2023 amendments) sets the maximum U-value for new entrance doors at 1.4 W/m`K in new dwellings. Best practice for premium residential projects targets significantly better performance — U-values of 1.0 W/m`K or below are achievable with modern steel door construction incorporating thermal breaks and insulated cores.

When specifying thermal performance, consider:

Whole-doorset U-value — not just the door leaf. Frame, threshold and glazing all contribute
Thermal bridging — steel is inherently conductive, making thermal break design critical. Specify continuous thermal breaks through the frame section
Psi values — for SAP calculations, the junction detail between doorset and wall affects the overall dwelling performance. Request psi values from the manufacturer
Air permeability — specify a maximum air leakage rate. Well-engineered steel doorsets achieve excellent airtightness due to precision manufacturing tolerances

Fire Resistance

Where fire resistance is required — communal entrances, flat entrance doors, doors in compartment walls — the specification must state the required rating and reference the relevant test standard. FD30 (30 minutes integrity) and FD60 (60 minutes integrity) are the common residential ratings. The doorset must be tested as a complete assembly including frame, hardware, glazing and intumescent seals.

The Fire Safety Act 2022 and Building Safety Act 2022 have tightened requirements for residential buildings, particularly those above 18 metres. Architects specifying entrance doors for higher-risk residential buildings should review the latest approved documents and consult the manufacturer on compliance. For detailed fire performance data, see our fire rated doors page.

Acoustic Performance

Acoustic specification for entrance doors is less standardised than security or thermal performance, but it is increasingly relevant for urban residential projects. A weighted sound reduction index (Rw) of 30-35 dB is typical for a well-constructed steel entrance door. Projects in noise-sensitive locations — adjacent to major roads, railway lines or flight paths — may require higher performance, achievable through enhanced sealing, laminated glazing and increased door leaf mass.

Specify the required Rw value and request test evidence from the manufacturer. Laboratory test results provide the most reliable data; field performance will typically be 3-5 dB lower due to installation variables.

Structural Considerations

Steel entrance doors present structural interface challenges that differ from lighter doorset types. Addressing these at the specification and detailed design stage prevents costly site remediation.

Weight

A bespoke steel entrance doorset — including leaf, frame, sidelights and hardware — can weigh between 120 and 300 kilograms depending on configuration. This has direct implications for:

Structural opening support — the lintel must be designed to carry the doorset weight plus any superimposed load. Steel lintels are typically required; timber or thin-gauge metal may be inadequate
Fixing strategy — heavy-duty mechanical fixings into masonry or structural steelwork. Chemical anchors into blockwork or concrete. The manufacturer should provide a fixing specification
Floor structure — the threshold and sub-floor must support the concentrated load at the hinge points without deflection or cracking

Opening Preparation

The structural opening should be prepared to tolerances tighter than those acceptable for lighter doorsets. Specify a maximum deviation of plus or minus 5 millimetres on width, height and diagonals. Out-of-square openings create problems with seal alignment, operation and long-term performance that are difficult to resolve after the doorset is installed.

For new-build projects, provide the doorset manufacturer with the structural opening dimensions at design stage and request a confirmed frame size. For refurbishment, a site survey by the manufacturer before production is essential — do not rely on approximate or historic drawings.

Structural Interface Detailing

The junction between doorset and surrounding wall requires careful detailing:

DPC and cavity tray continuity — the doorset must not bridge the damp-proof course or interrupt cavity tray arrangements
Thermal bridge mitigation — insulation must be continuous around the frame perimeter. Specify an insulation return detail
Weather sealing — external mastic, compression seals or a combination. The detail must accommodate differential movement between the doorset and the surrounding masonry or cladding
Fire stopping — where fire resistance is required, the perimeter gap must be filled with fire-rated material and intumescent sealant in accordance with the test evidence

Threshold Details

The threshold is the most technically demanding element of the doorset installation. It must simultaneously provide weather resistance, thermal performance, accessibility compliance and structural support.

Part M of the Building Regulations requires a maximum threshold height of 15 millimetres for new dwellings, with a ramped or chamfered transition. Specifying a level threshold (zero upstand) is best practice for accessibility but requires meticulous drainage and weather seal detailing to prevent water ingress.

Options include:

Aluminium threshold with thermal break — the standard solution, available in low-profile configurations
Recessed mat well — integrating a drainage channel and mat recess ahead of the threshold
Flush stone or tile threshold — achievable with careful coordination between the doorset manufacturer and the flooring contractor

Confirm the threshold detail with the manufacturer before construction reaches floor level. Retrospective threshold modifications are among the most common — and most avoidable — site problems.

Hardware Specification

Hardware for a steel entrance door must be specified as an integrated system rather than a collection of individual components. The locking mechanism, handle, cylinder, hinges and closer must all be compatible with the doorset's security rating and fire rating where applicable.

Key specification lines:

Multi-point locking — minimum three-point for PAS 24, typically five-point for SR3
Cylinder — anti-snap, anti-pick, anti-bump, anti-drill. Specify to TS 007 three-star or equivalent
Hinges — heavy-duty, adjustable hinges rated for the door leaf weight. Dog-bolt or hinge-side security bolts to resist hinge-side attack
Closer — concealed overhead closer for accessibility and aesthetics. Specify to BS EN 1154 with adjustable closing speed and latching action
Hardware finish — specify RAL or standard finish (polished brass, satin chrome, matt black, PVD bronze). Confirm finish compatibility with the security and fire ratings

Finish Specification

Steel entrance doors are finished with polyester powder coating as standard, applied in a controlled factory environment. The specification should address:

RAL colour — any colour from the full RAL Classic range. The full colour options available allow precise matching to the architect's intent
Coating thickness — minimum 60 microns for standard applications, 80-100 microns for coastal or high-exposure locations
Gloss level — specify as a percentage (typically 20-30 per cent for satin, 70+ for gloss)
Dual colour — many projects specify different colours for the external and internal faces. Confirm this as a requirement at specification stage
Guarantee — specify a minimum coating guarantee period. Quality manufacturers offer 10-25 years

For projects requiring a metallic, textured or specialist finish, discuss feasibility with the manufacturer early. Not all finishes are compatible with all security and fire ratings.

Sample and Approval Process

Bespoke steel entrance doors are significant architectural elements that warrant a formal approval process. The following sequence is recommended:

1. Initial consultation — share design intent, performance requirements and project programme with the manufacturer 2. Scheme design drawings — the manufacturer produces preliminary drawings showing doorset configuration, hardware positions and finish options 3. Colour and finish samples — physical RAL colour panels and hardware finish samples for approval. Always approve colour from a physical sample, never from a screen 4. Technical submission — full specification, test certificates, structural fixing details, threshold detail, hardware schedule 5. Approval drawings — dimensioned production drawings for formal sign-off before manufacture begins 6. Factory visit — for bespoke or high-value projects, a factory visit during production provides confidence in quality and allows minor adjustments before completion

Allow adequate programme time for this process. A typical bespoke steel entrance door requires 8-12 weeks from order to delivery, plus the approval period. Compressing the programme invariably compromises the outcome.

Working with Manufacturers

The quality of the specification is only as good as the manufacturer's ability to deliver it. When selecting a manufacturer for a bespoke steel entrance door, assess the following:

Certification — verify that claimed security, fire and thermal ratings are backed by current, valid test certificates from UKAS-accredited laboratories
Manufacturing quality — ISO 9001 certification provides a framework assurance. Factory visits provide direct evidence
Design capability — the manufacturer should have in-house design and engineering capacity, not simply a sales function
Project experience — ask for references on comparable projects, particularly in regulated environments (conservation areas, high-rise residential, listed buildings)
After-sales support — adjustment, maintenance and spare parts availability over the design life of the doorset

A collaborative relationship between architect and manufacturer produces the best outcomes. Engaging the manufacturer at RIBA Stage 2 or 3 allows performance constraints to inform the design rather than restrict it retrospectively.

CPD Opportunities

Manufacturers of bespoke steel entrance doors increasingly offer RIBA-approved CPD seminars covering security standards, fire performance, thermal design and specification best practice. These sessions provide genuine technical value and count towards annual CPD requirements.

Topics typically available include:

Specifying entrance doors to LPS 1175 and Secured by Design
Fire-rated doorsets under the Building Safety Act
Thermal performance and carbon reduction through improved entrance door specification
Balancing heritage aesthetics with modern performance requirements

Contact manufacturers directly to arrange CPD sessions for your practice or project team. The most productive sessions are those tailored to a live project, where the learning is immediately applicable.

Frequently Asked Questions

What is the minimum security standard for entrance doors in new-build projects?

PAS 24:2022 is the minimum security standard mandated by Approved Document Q for all new dwellings in England and Wales. This applies to the complete doorset — leaf, frame and hardware — tested as an assembly. For enhanced security, LPS 1175 SR2 or SR3 provides a graded system of physical attack resistance.

How do I specify a steel door that meets both fire and security requirements?

Dual-rated doorsets must be tested and certified for both fire resistance and security as a single assembly. You cannot combine separately certified fire-rated and security-rated components. Specify the required fire rating (FD30 or FD60) alongside the security rating (PAS 24 or SR class) and request evidence that the doorset has been tested to both standards simultaneously.

What U-value can a steel entrance door achieve?

Modern steel entrance doors with thermal breaks and insulated cores can achieve U-values of 1.0 W/m`K or better. The regulatory maximum for new dwellings under Approved Document L is 1.4 W/m`K. Specify the target U-value for the whole doorset, not just the door leaf, as the frame and threshold contribute significantly.

How heavy is a typical bespoke steel entrance door?

A single-leaf steel entrance door typically weighs between 80 and 150 kilograms depending on size, glazing and security rating. A double-leaf doorset with sidelights can exceed 300 kilograms. The structural opening, lintel and fixings must be designed to accommodate this weight.

What lead time should I allow for a bespoke steel entrance door?

Allow 8-12 weeks from confirmed order to delivery for a standard bespoke steel doorset. Complex configurations, specialist finishes or dual fire-and-security ratings may extend this to 14-16 weeks. The approval process — from initial consultation to signed-off production drawings — adds a further 2-4 weeks and should be programmed separately.

Can I specify different colours for the internal and external faces?

Yes. Dual-colour specification is standard practice for bespoke steel entrance doors. The external face is typically finished in the architect's specified RAL colour, while the internal face is finished to complement the interior scheme. Confirm the dual-colour requirement at specification stage as it affects the production sequence.