LPS 1175 D15 Security Rating Explained

LPS 1175 D15 certifies that a complete product has resisted an experienced attacker with a professional cordless toolkit, including 18V disc grinders and reciprocating saws, for at least fifteen minutes. It uses the same tools as D10 but adds five minutes of delay, and unlike the more familiar ratings it has no Issue 7 SR equivalent. This guide explains what D15 means, how it compares with D10 and E10, and when a longer delay is the right answer.

What Does LPS 1175 D15 Mean?

LPS 1175 is the Loss Prevention Standard for intruder resistant building components, published by the Loss Prevention Certification Board (LPCB), part of BRE Global. Issue 8 classifies performance on a grid: a tool category letter from A to H, and a minimum delay of 1, 3, 5, 10, 15 or 20 minutes. Every combination is a possible rating, and D15 is the point where Category D tools meet a fifteen-minute delay.

At D15, the test team attacks the locked product with Category D tools and must not create a 400 mm x 225 mm opening, the minimum size a person can climb through, within fifteen minutes of working time. Any part of the assembly can be targeted, including the leaf, frame, glazing, infill panels, hinges, locks and fixings.

The Category D tool set

Category D is the point where power tools enter the test. It represents an experienced criminal with a professional cordless toolkit, prepared to make noise and work for a sustained period. The kit includes everything in Categories A to C plus:

• Categories A to C: hand tools, bolt cutters, a claw hammer, a cordless drill, an axe, a crowbar, a lump hammer, cold chisels and a gas torch
• Added at Category D: 18V cordless disc grinders, reciprocating saws, jigsaws, circular saws and sledgehammers

The tools are identical to D10. What changes is endurance: a D15 product has to keep resisting cutting, leverage and impact for half as long again, which usually means heavier sections, tougher infills and more robust locking.

D15 vs D10 and E10: Longer Delay or Stronger Tools?

The Issue 8 grid means ratings can increase in two directions. Moving right along the grid adds more powerful tools; moving down adds more time. D15 and E10 both sit above D10, but they are not steps on the same ladder.

Why D15 Has No SR Equivalent

Issue 7 used a single SR1 to SR8 scale, where each step changed the tools and the time together. When Issue 8 came into effect in 2019, it separated the two, which created ratings that Issue 7 had no way to express. SR4 is compared with D10 and SR5 with E10, but nothing in Issue 7 described Category D tools for fifteen minutes.

That matters when reading specifications. A document that only uses SR ratings cannot call for D15, so a D15 requirement normally comes from a newer specification or a threat assessment written around Issue 8. If an older specification calls for SR4, D10 is the comparable Issue 8 rating, not D15.

Matching the Delay to the Response

The delay in an LPS 1175 rating is only useful if someone can respond within it. That is the main reason to specify D15 over D10:

• Detection: the delay only helps from the moment the attack is detected, so alarms and monitoring need to raise the alert early.
• Response time: where the expected response takes longer than ten minutes, a fifteen-minute delay keeps the product holding until help arrives.
• Matching structure: the wall, slab or foundation around the product needs equivalent resistance, or the attacker will simply go round it.
• Layered protection: perimeter, envelope and internal layers each add delay. Each certified layer keeps its own rating; two D10 layers do not make a D15 product, but together they extend the time an attacker needs.

Where D15 Is Specified

D15 suits sites where the credible threat is an experienced attacker with power tools, but a response would take longer than D10 allows. Typical applications include:

• Remote and unmanned utility sites
• Rural infrastructure and substations
• Telecoms and remote equipment sites
• Edge and regional data centres
• Large sites monitored off-site
• Out-of-hours commercial and logistics sites

As with any rating, the requirement should come from a security risk assessment that weighs the asset value, the likely attacker and the time a response needs to arrive. In critical infrastructure contexts, that assessment is typically informed by NPSA (National Protective Security Authority) guidance.

Specifying a D15 Product: Checklist

• Confirm the product holds an LPCB certificate showing D15 under Issue 8 (both the letter and the number), and check the current listing on Red Book Live
• Make sure the specification asks for D15 because of the response time, and not as a substitute for E10 where stronger tools are the real threat
• Check that the certificate covers the exact configuration, size and opening direction being specified
• Use only the locking systems listed on the certificate; other locks do not carry the rating
• Design the surrounding wall, slab or foundation to match the attack resistance of the product
• Detail fixings and the connection to the structure, which sit outside the certificate
• Plan an uninterrupted power supply for powered locking and access systems if the rating must hold during a mains failure
• Remember that resistance of access control systems to non-mechanical attack is outside the scope of LPS 1175

Frequently Asked Questions: LPS 1175 D15

Related Premier Security Resources

• LPS 1175 Security Ratings Explained: the full SR1 to SR8 and A1 to H20 guide
• LPS 1175 D10 / SR4 Rating Guide: the same tools with a ten-minute delay
• LPS 1175 E10 / SR5 Rating Guide: more powerful tools with a ten-minute delay
• LPS 1175 C5 / SR3 Rating Guide: the Category C hand tool rating
• Contact Premier Security: technical consultation and project enquiries