LPS 1175 vs ASTM: what the SR ratings mean and how they compare

If you have been shopping for a security door, you have probably seen “LPS 1175 SR2” or “SR3” next to a product and had no idea whether that number matters or how high it needs to be. It is one of the most quoted security ratings in the UK and one of the least explained. Here is what LPS 1175 actually measures, how the SR scale works, and how to read it against the US ASTM standard.

What LPS 1175 actually measures

LPS 1175 is a Loss Prevention Standard. It rates how well a product resists a deliberate, tooled attempt at forced entry. Testing is carried out by the LPCB, an independent certification body, so the rating is a test result rather than a marketing line.

The key point is that the standard measures the whole assembly. A door is tested with its frame, fixings and locking as one unit, because a strong leaf hung in a weak frame fails at the frame. When you see an SR rating on a product, it belongs to that tested combination, not to the door panel on its own.

If what you actually want is the list of standards the doors we supply are built and tested to, rather than the detail of how the scale works, that is set out on our certifications page.

How the SR ratings work

Ratings are written as SR followed by a number. Each rating fixes two things: the toolkit an attacker is assumed to bring, and the minimum time the product must resist entry with those tools.

Lower ratings assume opportunist tools and shorter attacks. Higher ratings assume a wider set of tools, more force, and a longer working time before the tester is allowed through. So moving up the scale is not simply a matter of a heavier door. It reflects a harder, better-equipped, more patient attack that the product has to hold out against.

That is why “which SR do I need” is really a question about the threat, not about picking the biggest number on the page.

What each SR rating means in practice

The SR scale runs from SR1 to SR8, and since Issue 8 each SR rating also has a two-part equivalent, explained further down. The four ratings a homeowner is likely to meet are set out below; the ratings above SR4 are specified for sites with a specific, elevated threat and are rarely relevant to a house.

Rating	What it resists	Where it is specified
SR1	Casual, opportunistic attack with improvised tools	Low-risk properties
SR2	A more sustained attack with standard tools	Homes with an elevated risk
SR3	A determined, tooled attack with a range of hand tools, tested against severe forced-entry attempts	Most homes that want a certified security door; the level our steel doors are built and tested to
SR4	A heavier, sustained attack with powered tools	High-risk properties, available as an option on steel

The exact toolkit and minimum attack time for each rating are defined in the standard itself and belong on the certificate, not on a sales page. If a supplier cannot show you the certificate that names the rating, treat the number as unproven.

LPS 1175 vs ASTM: how the two standards compare

LPS 1175 is the UK manual-attack standard. It is published by the LPCB and the result is written as a security rating. ASTM International is the United States standards organisation, and its forced-entry methods, including ASTM F476 for swinging door assemblies and ASTM F3038 for timed forced-entry evaluation, are separate test methods with their own procedures and their own way of rating the result.

	LPS 1175	ASTM (F476, F3038)
Origin	United Kingdom, published by the LPCB	United States, ASTM International
How the result is written	A security rating: SR1 to SR8, or since Issue 8 a tool category and a delay in minutes, such as C5	Set by each ASTM method
What is tested	The complete doorset, leaf and frame together	F476: the door assembly, including hinge, lock, strike and jamb. F3038: complete units in a test frame

The two do not convert. They are separate tests with separate ways of writing the result, so an ASTM result cannot be read straight across to an LPS 1175 security rating, and a supplier offering a clean one-for-one match is oversimplifying. If a specification calls for LPS 1175, an ASTM result is not a substitute, and the reverse is also true.

For a UK home, look for the UK standards, and LPS 1175 is one of them. It was first developed for UK insurers, Secured by Design lists it among the standards it accepts, and it is the scheme the doors we supply are built and tested to. If you are comparing two doors and only one of them can name a UK standard, you are not comparing like with like.

One thing to watch when you compare ratings. LPS 1175 has been revised several times, and Issue 8 changed how a rating is written. Earlier issues used SR1 to SR8. Issue 8 pairs a tool category, A to H, with the minimum delay in minutes the product achieved: 1, 3, 5, 10, 15 or 20. So C5 means the product resisted Category C tools for at least five minutes. The SR ratings were kept as an option and each one matches a two-part rating: SR1 is A1, SR2 is B3, SR3 is C5, SR4 is D10, SR5 is E10, SR6 is F10, SR7 is G10 and SR8 is H20. Products approved to an earlier issue can keep that approval, but the manufacturer has to say which issue it is. So when you compare two doors, check which issue of LPS 1175 each certificate names and which form of the rating it uses, rather than assuming the numbers line up.

The standards behind every door we fit are set out on our certifications page.

Which rating you actually need

For most homes, the lower ratings, typically around SR1 to SR3, are what get specified. They are aimed at the forced-entry attempts a domestic property is realistically likely to face. Higher ratings exist for sites with a raised or specific threat, and specifying above the assessed risk mostly adds cost rather than useful protection.

The honest answer for a front door is that the right rating comes out of a survey, not a web page. Our steel front doors are built and tested to SR3, with SR4 as an option, but the rating for your door should follow that survey rather than lead it. The same survey-first approach applies across every front door we fit, whatever the material.

How to check a rating is genuine

A rating is only as good as the certificate behind it. Before you rely on an SR claim, ask for the certificate that names the exact product and the exact rating, and check that the door being quoted is the one that was tested, within its certified size range. If the claim you are checking is a Secured by Design one rather than an SR rating, our guide to what makes a door Secured by Design explains what that scheme actually certifies.

On our certifications page we set out the standards the products we supply are tested against, so you can see the evidence rather than take the adjective. Forty years in the security trade has taught us that buyers make better decisions when the proof is in front of them.

If you want a straight answer on the rating your door should hold, book a free site survey and we will give you a written quote with the specification set out in plain terms. You can arrange that through our contact page.