Metador metador defender thermaguard steel insulated steel doorsets

Metador Defender ThermaGuard – Insulated Steel Doorset

The Metador Defender ThermaGuard is a made-to-measure insulated steel doorset built for projects where thermal efficiency matters just as much as strength and durability. Designed to achieve U-values as low as 1.4 W/m²K, it allows specifiers to meet or exceed Part L requirements without having to compromise on the robustness of a steel door.

Verified thermal performance

ThermaGuard doorsets combine a thermally broken frame, mineral wool insulated core and upgraded perimeter sealing to minimise heat loss around the opening. The system has been independently assessed by a UKAS-accredited body in line with BS EN 10077-2, so the thermal performance figures you see are tested and verified, not just estimated.

How it's built

Each door leaf uses two 1.5mm galvanised steel skins folded and mechanically locked around a mineral wool core with internal steel strengtheners, creating a rigid 45mm thick insulated panel. This sits within a 90mm deep single-rebate frame made from 2mm galvanised steel, paired with a DDA-compliant stainless steel threshold and tubular seals that work together to deliver excellent air-tightness.

The standard configuration achieves around 1.4 W/m²K on a single door, with options to improve this further through careful glazing specification and coordination with the surrounding building fabric.

Single or double doors, with glazing options

ThermaGuard is available as single or double doorsets, opening inward or outward, and can include matching overpanels or side panels for larger openings. Vision panels can be positioned and sized to suit the design, with double or triple glazing available in clear, obscure, patterned or privacy glass. Solid, glazed or louvred side and transom panels complete the entrance while keeping the thermal strategy intact.

Security and fire-rated variants

Within the ThermaGuard range there are options that combine low U-values with PAS 24-tested security performance, as well as fire-rated versions offering up to 120 minutes protection (subject to size and hardware limitations). This means you can specify a thermally efficient steel door for applications that also have strict fire or security requirements.

Hardware and finish flexibility

ThermaGuard works with a full range of hardware, from standard commercial locks through to high-security multipoint systems, panic bars and access control-ready lock cases. Stainless steel ball-bearing hinges with security dogbolts are fitted as standard, with concealed or continuous hinge options available where needed.

Doors are powder-coated in any standard RAL or BS colour, with marine-grade or special effect finishes (textured, metallic, woodgrain) available for demanding environments or architect-led schemes. Acoustic performance can also be enhanced where noise control is required alongside thermal efficiency.

Where to use ThermaGuard

This doorset is ideal for any external door on a heated building where a traditional steel door would cause unacceptable heat loss. Typical uses include plant and boiler rooms, warehouse access doors, commercial back-of-house entrances, and mixed-use or residential projects where a steel door is preferred but Part L compliance is essential.

The Defender ThermaGuard is designed for any building where a steel door is required but thermal efficiency cannot be compromised. It bridges the gap between standard steel security doors (which typically have poor U-values) and the stringent thermal performance requirements of modern UK Building Regulations.

Part L compliance and energy-efficient buildings

Since the 2021 updates to Part L of the Building Regulations, thermal performance standards for doors have become much tighter. The ThermaGuard doorset, with U-values as low as 1.4 W/m²K, is specifically engineered to meet or exceed these requirements for non-domestic and domestic buildings in England, Scotland and Wales. This makes it a compliant, tested solution for projects targeting BREEAM, Passivhaus or net-zero carbon standards where every element of the building fabric is scrutinised.

Commercial and industrial buildings

• Plant and boiler rooms: External access doors to heated spaces containing mechanical services, where heat loss through a standard steel door would be unacceptable.
• Conditioned warehouses and cold stores: Secure personnel access doors that minimise temperature loss while still offering the strength and durability of steel.
• Data centres and comms rooms: Where precise environmental control is critical and every potential thermal bridge must be managed.
• Commercial kitchens and back-of-house: Fire exits and delivery doors on heated premises, particularly where insurance or lease terms require robust construction alongside thermal compliance.

Educational, healthcare and public buildings

• Schools and colleges: External doors on heated corridors, plant rooms and service areas where Part L compliance is mandatory and vandal resistance is also a concern.
• Hospitals and care homes: Secure external access points that must balance infection control (minimising draughts), fire safety and thermal efficiency.
• Leisure centres and sports facilities: Pool plant room doors and service entrances where high humidity, temperature differentials and heavy use demand a durable, thermally efficient solution.

Residential and mixed-use developments

• Apartment blocks: Communal plant room doors, bin store access and fire escape doors where thermal performance affects the overall SAP or EPC ratin

Metador Defender ThermaGuard Specification

Maximum doorset dimensions

• Single door max width: 1284 mm
• Single door max height: 2400 mm
• Double door max width: 2500 mm
• Double door max height: 2400 mm
• Configuration: Inward or outward opening, single or double leaf

Thermal performance

• Standard U-value: 1.5 W/m²K (with 60 mm door leaf and 110 mm frame)
• Enhanced U-value: 1.4 W/m²K (with 70 mm door leaf and 120 mm frame)
• Independently assessed in line with BS EN 10077-2 by a UKAS-accredited body
• Part L compliant for England, Scotland and Wales

Door leaf construction

• Material: 1.5 mm galvanised steel, double-skinned
• Thickness: 60 mm (standard) or 70 mm (enhanced thermal spec)
• Core: Mineral wool insulation with internal steel strengtheners
• Construction: Weld-free assembly to prevent premature failure at joints
• Edge detail: Anti-jemmy flange on leading edge (square edge option available)

Frame construction

• Material: 2.0 mm galvanised steel
• Depth: 110 mm (standard) or 120 mm (enhanced thermal spec)
• Profile: Single rebate, thermally broken design
• Corners: Bolted for structural integrity
• Fixings: Threaded adjusters for precise site installation (16+ fixing points). Plain fixing plates available as an alternative
• Hinge brackets: 3 mm steel for increased strength and security

Seals and weatherproofing

• Tubular silicone rubber seal bonded to the sub-frame perimeter
• Provides weather, thermal and acoustic performance when the door is closed

Threshold options

• Standard: DDA-compliant chamfered profile in 2 mm stainless steel
• Alternative profiles: Raised or extended cills, inward-opening profiles with drainage channel, or 4 mm ramped design
• Removable threshold: Available for accessibility or maintenance requirements

Hardware and ironmongery

• Hinges: Stainless steel ball-bearing hinges (4+ per leaf) with security dogbolts as standard
• Upgrade options: Concealed hinges, heavy-duty continuous hinges, or special finishes
• Locking: Wide choice of lock types including high-security multipoint locks, sashlocks, access control-ready cases, and panic hardware
• Handles and trims: Configurable to suit project requirements and performance specifications
• Hardware selection must be coordinated with fire, acoustic or security ratings where applicable

Glazing options

• Vision panels available in custom sizes and positions
• Double or triple glazing options (clear, obscure, patterned, or privacy glass)
• Glazing specification affects overall doorset U-value

Finish options

• Polyester powder coating in any standard RAL or BS colour
• Marine-grade finishes available for coastal or harsh environments
• Special effects: Textured, metallic, or woodgrain laminates

Enhanced performance options

• Fire rating: Available up to FD120 (120 minutes) subject to size and hardware limitations
• Acoustic rating: Enhanced acoustic configurations available for noise-sensitive applications
• Security: PAS 24-tested variants available where certified security is also required

Installation Guidance – Metador Defender ThermaGuard

The Defender ThermaGuard doorset is supplied as a factory-assembled steel frame and door leaf to simplify installation on site. It uses Metador’s threaded frame adjuster system, allowing the frame to be accurately plumbed and levelled without excessive packing. Correct installation is essential to maintain thermal performance, weather resistance and any fire or security ratings.

Pre-installation checks

• Confirm the structural opening dimensions match the doorset size stated on the delivery paperwork.
• Check the opening is square and plumb using a spirit level on both jambs and the head.
• Ensure the floor or threshold area is level – any significant deviation must be corrected or packed so the frame head remains straight.
• Inspect the doorset for transit damage before installation; any issues should be reported prior to fitting.

Tools and fixings

• Hammer drill / SDS drill and appropriate masonry bits.
• Impact driver or cordless drill/driver.
• Long spirit level.
• Large hex key (supplied with the doorset) for threaded frame adjusters.
• Spanners/sockets for frame fixings.
• Suitable structural fixings for the substrate (concrete, blockwork or steel).
• Silicone or appropriate sealant, plus fire‑rated mastic where required for fire‑rated doors.

Fitting the frame

1. Separate the leaf and frame (if required): Remove the door leaf from the hinges to make the frame lighter and easier to handle.
2. Position the frame: Lift the frame into the opening and roughly centralise it, checking there is an even gap to the surrounding structure.
3. Set the adjusters: Use the supplied hex key to wind out the threaded frame adjusters until they lightly contact the surrounding wall and hold the frame in place.
4. Plumb the hinge jamb: Using a spirit level, adjust the hinge side jamb until it is perfectly vertical in both planes. This is the most critical part of the installation.
5. Fix the hinge jamb: Once plumb, drill through the fixing points on the hinge side and install the first fixing at the top. Re‑check alignment, then continue down the jamb, fixing at each point while maintaining plumb.
6. Check the head: Confirm the head of the frame is level. Pack under the frame feet if necessary to correct any floor variation.

Hanging and aligning the door leaf

1. Re‑hang the leaf: Mount the door leaf back onto the hinges and check it swings freely without fouling the floor or threshold.
2. Set gaps: Close the door and check the gap between the leaf and frame along the head and hinge side (typically around 3–4 mm and consistent).
3. Adjust the lock side: Use the frame adjusters on the lock jamb to bring it into alignment with the leaf so the closing gaps are even from top to bottom.
4. Fix the lock jamb: Drill and secure the fixings on the lock side, checking the door operation after each fixing to ensure the latch and any multipoint locks engage smoothly.

Threshold and sealing

• Ensure the stainless steel threshold sits on a level, solid base; bed it on a bead of sealant before final fixing to minimise water ingress.
• For outward‑opening doors, pay particular attention to the external seal line to prevent wind‑driven rain penetration.
• Once final alignment is confirmed, seal around the frame perimeter internally and externally with an appropriate sealant.
• For fire‑rated ThermaGuard doorsets, use only the specified intumescent mastics and follow the fire installation instructions supplied with the door.

Final checks and commissioning

• Open and close the door several times to confirm smooth operation and positive latching without slamming.
• Check all hinges, dogbolts and hardware fixings are tight.
• Verify that weather seals make continuous contact around the leaf when closed.
• If door closers are fitted, adjust closing and latching speeds so the door closes fully without excessive force.

Full, product‑specific fitting instructions are supplied with each ThermaGuard doorset and should always be followed. Where installation may affect fire or security certification, a competent installer familiar with Metador steel doorsets should be used.

Metador Warranty & Guarantee

Our commitment to quality is backed by clear warranty terms designed to give you peace of mind. The Metador guarantee covers the following key components of your ThermaGuard doorset, subject to adherence to the specified maintenance regimes:

Warranty periods

• Frame & Doorset Structure: 15-Year Guarantee (Subject to correct installation and maintenance).
• Marine Grade PPC Finish: 10-Year Guarantee (Subject to documented cleaning and maintenance).
• Standard PPC Finish: 1-Year Guarantee (Subject to documented cleaning and maintenance).
• Ironmongery & Hardware: 1-Year Guarantee (Subject to correct usage and maintenance).

Guarantee coverage

Metador Ltd will repair or, at their discretion, replace any goods sold by Samson Doors that are proven to be defective within the stated warranty periods from the date of purchase.

• Component replacement: Where a product has a specific internal defective component, the warranty covers the replacement of that component only.
• Definition of defect: "Defective" goods are those which, under correct usage, fail to function properly due to faults in materials, workmanship, or design.
• Delivery defects: Any goods found to be defective upon delivery must be reported within 3 working days of receipt. Photographic evidence showing the defective goods on their original delivery pallet is required.

Guarantee exclusions

The Metador guarantee does not cover defects or damage arising from:

• Neglect & abuse: Damage caused by misuse, lack of maintenance, or unsuitable care.
• Chemical damage: Use of harmful cleaning solvents or abrasive agents on the door surface.
• Improper installation: Issues resulting from incorrect fitting, alignment, or installation practices.
• Surface damage: Scratches, washing damage, or failure of paint protection films after delivery.
• Unauthorised parts: Use of components or accessories not advised or supplied by Metador.
• External factors: Damage from external impacts, severe weather events, or environmental conditions not specified for the product (e.g., using a standard finish in a marine environment).
• Fair wear & tear: Normal degradation expected over the product's lifecycle.

Condition of warranty

Crucial requirement: For any guarantee or warranty to remain valid, a documented cleaning and maintenance regime must be maintained. You must record the frequency of maintenance, along with the specific methods and products used. This documentation must be submitted with any claim for it to be considered.

Claims procedure

1. Notification: You must contact Samson Doors in writing within 3 working days of discovering a defect, detailing the nature of the issue.
2. Inspection: On request, the defective product (or part) may need to be returned to Metador Ltd (at the customer's cost) for inspection.

For full details on care requirements, please refer to the Operation & Maintenance Manual available for download here.

A steel doorset is always ordered by the OVERALL dimensions including the door leaf and outer sub fixing frame with no tolerances allowed for. Most people would generally allow 5mm tolerance all the way around the door, but it all depends on how square or true your aperture is on site. This is up to your judgement based on the aperture quality.