SR3 and SR4 security doors

SR3 and SR4 security doors are steel doorsets tested to LPS 1175 for higher-risk sites. SR3, code C5, resists five minutes of attack with crowbars, drills and chisels. SR4, code D10, resists ten minutes with sledgehammers, disc cutters and jigsaws. ArxBridge supplies and installs both across the UK. They sit above SR2 in the security range.

• C5SR3: five minutes, crowbars and drills
• D10SR4: ten minutes, disc cutters and jigsaws
• SR3 and SR4For higher-risk sites
• Tested assembliesLeaf, frame and hardware as one

What SR3 and SR4 doors are

SR3 and SR4 sit above SR2 on the LPS 1175 scale. They answer a prepared attacker: someone who arrives with proper tools and a plan. The C5 test uses crowbars, drills and chisels for five minutes. The D10 test steps up to sledgehammers, disc cutters and jigsaws for ten minutes. These are the ratings insurers and security consultants name for cash handling, critical plant and high-value storage.

Construction is heavier than SR2 at every point. The leaf carries deeper reinforcement, the frame section is stronger, and the locking spreads across more points. As with every LPS 1175 rating, the test covers the complete doorset, and ArxBridge supplies third-party test evidence for the configuration ordered. The rating table is in the LPS 1175 guide.

Match the rating to the room. SR4 on a stationery cupboard wastes budget; SR2 on a cash office invites failure. Rate each opening from its own risk assessment.

Which rating do you need for sr3 and sr4 security doors

The jump from SR2 to SR3 is the most common upgrade on live projects: it answers the prepared attacker rather than the opportunist. SR4 follows where the asset or the function justifies ten minutes of resistance, or where an insurer names it. For the lower tier, see SR2 security doors.

How SR3 and SR4 doorsets are built

The leaf is a heavy steel shell with layered reinforcement around the lock case, hinge edge and meeting stile. At SR4 the leaf thickness and internal structure step up again to absorb disc cutter and sledgehammer attack for the full ten minutes. Edges are folded and welded so there is no seam to start a prising attack.

Frames are deep steel sections, anchored into the structure with fixings inside the test scope. Locking is multi-point as standard, engaging head, sill and jamb. Hinges are high-load and anti-lift; cylinders are high-security with drill and pull protection matched to the rating. Glazed options use thick attack-rated glass in a tested bead system, because at these ratings the vision panel is a favourite target.

SR3 and SR4 security doors with combined ratings

Fire and forced entry is a frequent pair at these levels: the doorset is tested to EN 1634-1 and LPS 1175 as one assembly (see fire and security doors). Where firearms are part of the threat, ballistic protection can be engineered into the same doorset (see bullet resistant doors). Blast ratings can be added for sites facing vehicle-borne attack (see blast resistant doors).

Each combination needs its own test evidence. A C5 rating and a fire rating on separate certificates do not make a dual-rated doorset; the assembly must be tested for both together. Name every rating at quote stage.

Where SR3 and SR4 doors are used

Banks and cash-handling sites use SR3 and SR4 on cash offices, strong rooms and ATM lobbies (see banking and finance). Utilities and energy sites protect control rooms, substations and fuel stores (see utilities and energy). Data centres rate the doors between security zones and on critical plant. Government buildings use SR4 where the threat assessment demands it. The pattern is consistent: the higher the value behind the door, the higher the rating on it.

What affects the cost and lead time of sr3 and sr4 security doors

The rating itself is the main cost driver at this level. SR4 uses more steel, more reinforcement and more machining than SR3, and the test programme behind it is longer. Size matters: tall or wide leaves need heavier sections to stay rigid under attack. Glazing is a significant addition, because the glass and its retention must meet the same rating as the leaf.

Hardware is specified to the rating, not chosen for looks: high-security cylinders, multi-point locks and access control all add supply time. Finishes range from standard powder coat to marine-grade systems for harsh sites. Quantities and site logistics, such as out-of-hours installation in live buildings, complete the picture. Quotes follow the schedule; no prices are listed.

How to specify SR3 and SR4 doors

1. Name the rating per door. Write “SR3 (C5)” or “SR4 (D10) to LPS 1175 Issue 8” against each opening.
2. Fix the configuration. Single or double leaf, solid or glazed, with swing direction.
3. Set the hardware grade. Cylinders, multi-point locks, closers and access control to suit the rating.
4. Check the wall. The frame anchorage depends on the surrounding construction; confirm it per opening.
5. Ask for evidence. Third-party test evidence for the exact doorset and rating, before manufacture starts.