Every new home in England has to let me visit. Almost none have to let me live there.

I can get into most new-build houses in this country. That's not luck - it's the law.

What I can't do is use the downstairs loo properly, get a chair round the ground floor, or sleep there. And that isn't a gap in the law either. That's the law working exactly as written.

The thing doing that is Part M. It covers access, it's the only part of accessible design that can stop a building opening, and it's the reason buildings are the shape they are.

It's also the part I get sent drawings about with "Part M compliant" written in the corner - when they aren't.

So here's what it says, what it refuses to say, and the handful of numbers I measure in nearly every building I walk into.

One thing first. Approved Document M covers England only - Wales, Scotland and Northern Ireland run their own standards.

Part M is law, and that's the whole problem

Part M is the legal minimum under the Building Act 1984 - and work that doesn't comply doesn't get signed off. That's a legal problem rather than a design one, which is why it's the only access document that reliably gets read.

BS 8300 is a British Standard. Best practice, far more detailed, and nobody can prosecute you for ignoring it.

So Part M gets built and BS 8300 gets filed. That's the dynamic, and it's why so many buildings sit at exactly the legal line and no further.

Here's the clearest version of it I know.

Part M wants grab rails in an accessible toilet and is relaxed about where they go. BS 8300-2 says 680mm to the top of the horizontal rail - and at least 600mm of usable length.

Both of those toilets pass Part M. Only one works if you're transferring out of a chair on your own, which is something I do several times a day and have opinions about.

And here's the part people miss. When somebody brings an Equality Act claim, the courts look at BS 8300 to decide what was reasonable. So a building can pass building control and still lose.

There are three kinds of new home, and only one is compulsory

The 2015 edition split new housing into three categories. The gap between them is the whole argument about accessible housing in this country - and almost nobody outside the trade knows it exists.

The first, M4(1), is mandatory for every new home. A 900mm approach, a 775mm front door, a threshold no more than 15mm high, and a WC on the floor you come in on.

The second, M4(2), gets built only when the planning authority asks. Level threshold instead of a step. An 800mm door. A 900mm staircase, so a stairlift can go in later. Walls strong enough to take a grab rail or a hoist.

The third, M4(3), is also only on a planning condition. 825mm doors throughout, 1200mm corridors, 1500mm turning circles, and a wheelchair-accessible bathroom on the entrance floor.

Read those again as somebody who uses a wheelchair, because they describe three completely different lives.

M4(1) means I can come to your house for an hour. I'll get through the front door - and I'll use a toilet built for somebody who can walk a bit and hold a rail, not for somebody who transfers out of a chair.

M4(2) means your house could be adapted for me later, without anybody tearing it apart.

M4(3) means I could move in.

Only the first one is compulsory.

Every new home in England has to be visitable. Hardly any have to be livable. A country with a housing crisis and an ageing population is still building, by default, homes most disabled people can enter and cannot stay in.

And M4(2) is cheap - wider doors, a level threshold, some timber in the right walls, all decided at drawing stage. Retrofit those same things in ten years and it's expensive, disruptive and sometimes impossible. It should be the default. It isn't, and the only reason is that nobody has made it one.

The numbers I actually end up measuring

Volume 2 covers everything that isn't a house - offices, shops, schools, hospitals, hotels, leisure centres. That's about eighty per cent of my work, and four things account for most of what I find.

Opening force, 30 newtons maximum at the leading edge. It's the one that fails most - and it fails for a reason nothing to do with design. Somebody complains the door slams. A caretaker winds the closer up. Nobody writes it down. Six months later it's a 45 newton door and the drawing still says 30. It's a gauge reading rather than a judgement, which is the only reason that argument is winnable.

The accessible bay, 2400 by 4800, with a 1200mm access zone between bays and at either end. I check the zones harder than the bay, because the bay is nearly always there and the zones are nearly always parked in. A bay with a van in the access zone isn't a bay - it's a space I can't get out of once I'm in it.

The transfer space, 950mm clear beside the WC in a room that wants to be 1500 by 2200. Clear means clear. Not clear apart from the bin, the sanitary unit, the box of hand towels and the mop. Every current toilet figure, with the document it comes from, is on the dimensions page.

And the alarm. A pull cord with two red bangles - one about 100mm off the floor, one between 800mm and 1000mm. That cord is the most common failure I find in any building anywhere. Tied up out of reach. Looped round itself. Knotted to the grab rail so it stops dangling.

Every one of those is somebody being tidy. And every one means the alarm can't be reached by a person lying on the floor, which is the only circumstance it exists for. The bangle at 100mm isn't a flourish - it's set at the height of somebody who has already fallen.

Those four are maintenance failures. Somebody adjusted, parked, stored or tidied - and the building drifted out of compliance without anybody deciding to. Three more get designed wrong instead, and they're much harder to put right afterwards.

Dead ends. A corridor wants 1200mm of clear width, 1800mm where two wheelchair users might meet, and 1800mm to turn round at the end of it. The turning space is the one that gets forgotten - because on a plan a dead end is just where a corridor stops. In a building it's the moment you work out you have to reverse the whole way back.

Lifts. Public access on more than one floor means one, and the car wants to be at least 1100 by 1400, 1400 square if somebody is going to turn rather than back out, with an 800mm door and controls between 900mm and 1200mm. Platform lifts are a last resort and I write them up as one. They're slow, they're small and they break - and when one breaks, your upper floor closes to me without anybody noticing.

Audience seating. Two wheelchair spaces up to a hundred seats, six up to five hundred, one per cent of capacity up to a thousand, then ten spaces plus half a per cent of everything above that, at 900 by 1400 each. What the numbers don't say, and what I write down every time, is that a space needs a seat beside it for whoever came with me - and a sight line that isn't the back corner. Two compliant spaces facing a stanchion tells you exactly how much thought went in.

The rest is widths and gradients - 1500mm routes, 800mm doors, 1:20 before a slope becomes a ramp. Worth knowing, and not where buildings actually go wrong.

Two things changed recently and a lot of people haven't caught up

Changing Places toilets became an Approved Document M requirement on 1 January 2021, through the 2020 amendment. Certain new and materially altered buildings in England have to have one: assembly, recreation and entertainment buildings for 350 people or more, plus large retail, sport, healthcare and transport. Below those thresholds it's an Equality Act argument rather than a Part M requirement.

I still read reports by other consultants calling Changing Places "best practice, not yet mandated". It was, once. It hasn't been for five years - and if that's in your report, your client is being told the wrong thing about the law.

Then on 1 October 2024, Approved Document T came into force covering toilets in buildings other than dwellings - and Part M was amended to point at it. Toilets in anything built or altered since then answer to both, and I've written up what Part T actually changed separately.

The current Approved Document M Volume 2 is the 2015 edition with the 2020 and 2024 amendments in it. Working from the 2016 amendments puts you two cycles behind.

Passing Part M is not the same as not getting sued

The Equality Act duty on service providers is anticipatory, and that one word does all the work.

It doesn't mean you handle it well when a disabled person turns up with a problem. It means you were supposed to have thought about it before they arrived. It isn't about if a disabled person comes along. It's about when. Whether an access audit is itself a legal requirement is a different question, and the answer is more interesting than it sounds.

So a compliant toilet with the cord tied up still fails. A compliant entrance everybody walks through except wheelchair users, who go round the side and ring a bell, still fails. The measurement passed. The duty didn't.

That gap is where I spend most of my working life. It's why I keep "this is unlawful" in a different sentence from "this could be better" - running them together is how access advice ends up in a drawer.

Now think about the person who doesn't tell you

I'm a difficult customer to ignore. I turn up with a tape measure, a lux meter and a force gauge, I know which document says what, and I write it down.

Almost nobody does that.

What happens instead is somebody arrives, finds the bay blocked or the door too heavy or the lift out, works out in about four seconds that this will cost more than the thing they came for - and goes home. They don't complain. Complaining means explaining your body to a stranger at a desk while a queue watches.

So you record no demand, and you conclude there isn't any. No complaints is the symptom. It has never once been the all-clear.

That's the real reason I measure instead of asking how a place feels. A number survives being forwarded to a finance director. Somebody's bad afternoon doesn't, because they never reported it.

Lawful doesn't always mean good enough

When I go into a building that just scrapes Part M I can tell before anybody says anything. The doors are tight. The spaces are minimum. Everything is exactly as much as somebody had to do and not a millimetre more.

When I go into a building designed past it, I don't notice the access at all. I notice the building.

That's the difference - and it's the whole reason I measure anything. Part M is the law, so meet it. It's also the floor, and nobody has ever been thanked for standing on a floor.