Thermally Rated Steel Door

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Steeldor thermal was developed to comply with door efficiency targets stipulated by the government in Part L of the updated Building Regulations. The leaf has an insulated, internal Rockwool core enabling it to achieve a U-value as low as 1.5 W/m2K, compliant with the guidance of 1.6 for new dwellings and 1.8 for new commercial buildings in England.

The UK government has committed to reducing carbon emissions and meeting its target of net-zero emissions by 2050. In line with this, several changes have been made to the building regulations to improve the energy efficiency of buildings. One such change is to Part L of the building regulations, which sets minimum standards for the U-values required for a steel door.

  • Expandable sides as standard
  • Thermally rated insulated core
  • Keeps the heat in and the cold out
  • Huge range of hardware options avaliable
Unique Range Features

Fast quotes
Easy fit doors
10-15 day lead time*
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Download Tech Specs
Made in Britain Colour

Product Features

Height Icon

Single - up to 2.96m
Double - up to 2.96m

Width Icon

Single - up to 1.4m
Double - up to 2.7m

Leaf Thickness

44mm deep leaf skin

Air permeability

EN1026:2000 to class 4 – 600Pa (113kmh) test pressure

Water tightness

EN1027:2000 to 150Pa for outward opening and 100Pa for inward

Resistance to wind load

EN12211:2000 to 1200Pa (Class A3) 98 mph

Thermal transmittance - U-value

Single - As low as 1.6 W/m2K
Double - As low as 1.5 W/m2K

Weather tightness

BS 6375: Part 1: 2009 (test to EN1026:2000, EN1027:2000, EN12211:2000) to 1200 exposure rating

Strongdor Icons Acoustic

Up to 39dB rating.

Further information


Manufactured from lightweight, high tensile 1.5 mm thick ‘Rustec’ steel. Adjust 2-Fit side expander system that offers up to 12mm expansion to the structural opening.

44mm door leaf thickness, fitted with a flush lipped astragal for added security. Comprising of 2 x 1.2mm ‘Rustec’ steel sheets, the leaf is internally bonded with a dutch fold stitch welded system providing greater stability and protection against de-lamination.  Rockwool insulated core. 

Door ironmongery
BS 7352 Grade 13 stainless steel, twin bearing template drilled butt hinges with integral high-security dog bolts are fitted as standard with CE marking. Other hardware on request.

Supplied inclusive of a powder-coated finish in a standard colour. Full range of RAL and BS colours available. 

Options and upgrades
Available as PAS 24: 2016.

Strongdor Steel Door Single Install Thumbnail

Single Door Installation

This video contains detailed, step-by-step instructions for the safe installation of a Strongdor Steeldor single door-set. Please pay particular attention to the safety instructions.

Strongdor Double Door Install Thumbnail

Double Door Installation

This video contains detailed, step-by-step instructions for the safe installation of a Strongdor Steeldor double door-set. Please pay particular attention to the safety instructions.

Touching Up Paintwork

Touching up Paintwork

A demonstration of how to sue the touch up kit supplied with your steel door-set.


Steeldor - Emergency Exits & Personnel Doors

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Firedor Thermal - Emergency Exits & Personnel Doors

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Steeldor Thermal - Emergency Exits & Personnel Doors

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Frequently Asked Questions

Who is responsible for ensuring the sales quotation meets the specification and building regulations, including location and method of installation?

It is the customer’s responsibility to ensure all details within the sales quotation / sales order meet the exact specification and / or original enquiry and are compliant with current building regulations including location and method of installation.

We are here to help and advise only and cannot accept responsibility for discrepancies after the order is confirmed.

Strongdor Terms and Conditions

Do Strongdor offer a site measuring or an installation service?

No, Strongdor are a supply only manufacturer and therefore unfortunately don't offer site surveys or installation. However we can recommend local installers in your area from our Doorfit Network, who will be happy to help.

Complete our quotation request form, mention you are looking for installation and we will put you in touch!

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