Security Doors

A commercial security door is one of the most important investments a business can make in protecting its assets, staff, and premises. Unlike a standard commercial entrance door, a properly specified security door is engineered from the ground up to resist physical attack, and its performance is independently verified through structured testing rather than manufacturer claims.

Sigma Shop Fronts supplies and installs commercial security doors across a broad range of applications — back-of-house access points, warehouse and depot entrances, plant rooms, server rooms, cash-handling areas, and anywhere else where the consequence of an unauthorised breach is severe.

Standards and Security Ratings

Two principal standards govern the tested performance of commercial security doors in the UK. LPS 1175 (Loss Prevention Standard 1175), published by the LPCB (Loss Prevention Certification Board), tests door sets against attack using progressively more capable tools over defined time periods, producing a rating from SR1 (basic resistance, hand tools only) through to SR8 (resistance to sustained attack with heavy plant). The LPCB maintains a publically searchable Red Book of certified products, allowing insurers and specifiers to verify the rating of any door set they are considering.

STS 202 (Security Tested Standard 202), published by the LPCB's sister organisation, follows a similar attack-testing methodology and is sometimes preferred by specific insurers or procurement frameworks. Many commercial insurers specify a minimum LPS 1175 SR2 or STS 202 BR2 rating for back-of-house entrances in high-value retail or commercial premises.

Construction: Steel vs Composite

Steel security door leaves are fabricated from cold-rolled steel sheet, typically 1.5–3 mm in thickness, reinforced with internal steel box sections. The outer face may be smooth, embossed, or finished with a polyester powder coat. Steel doors are exceptionally strong and can be manufactured to accept very high-security locking systems, but they are heavy (a 1.0 × 2.1 m single-leaf door can exceed 80 kg), which imposes demands on the frame and hinges.

Composite security doors use a laminated construction — steel skins bonded to a rigid foam or honeycomb core. This approach provides excellent stiffness-to-weight ratio, improved thermal insulation compared to solid steel, and resistance to the peel and lever attacks that exploit the bond line between face sheet and frame on lower-quality doors. Our composite range includes door sets tested to LPS 1175 SR2 and SR3.

Door Frames and Installation

A security door is only as strong as its frame and its fixing into the surrounding structure. We install all security doors with purpose-designed steel sub-frames or knock-box frames that are fixed through to the structural wall using torque-controlled anchor bolts at centres determined by the load calculations for the specified security rating. Where the structural wall is constructed from materials with lower pull-out resistance (dense concrete blocks, for example), we use resin anchors to achieve the required fixing capacity.

Frame depth is matched to the wall thickness, and all perimeter joints are filled with fire-rated intumescent material where the door set forms part of a fire-compartment boundary.

Locking Systems

Our standard commercial security doors are supplied with a multi-point locking mechanism engaging the frame at a minimum of five points — top, bottom, and three along the strike side. The lock body is a high-security euro profile cylinder resisting to TS 007 3-star or equivalent, offering anti-drill, anti-pick, and anti-bump protection. Master-keying and key-alike suites are available for multi-door installations.

Where a door is used as a means of escape, we specify panic hardware conforming to BS EN 1125 (panic exit devices) or emergency exit devices conforming to BS EN 179. The distinction is important: BS EN 1125 covers single-action operation regardless of the user's ability or awareness, whereas BS EN 179 permits a lever or knob that requires a specific action. The fire strategy and means of escape design for the building determines which standard applies.

Access Control Integration

Security doors can be supplied with integrated access control provisions — electric strikes, magnetic locks, door controllers, and card or PIN reader mounting plates. We work alongside access control specialists and, where required, coordinate the door hardware specification with the access control installer to ensure compatibility between the mechanical and electronic elements of the system.