Understairs toilet - building regs

[Juno231]

I'm in a Victorian semi in London and am looking to do a side return extension on the ground floor - along with it we're wanting to add a utility room and a downstairs toilet. I always assumed this toilet could go under the stairs but our architect is now saying that wouldn't be compliant with building regs.

According to her it needs to be 900mm wide and we have 685mm (although I'm not sure how that's measured as it looks like 800 when I do it?). Thing is if I look at floor plans for the same houses on my street, several of them have put loos under the stairs, same with a bunch of pics I've saved off of Instagram that even explicitly state 685mm!

So are all of these people not compliant or have the regs changed this year? Or is it because my architect is trained in Scotland and is getting confused with the Scottish regs 😅.

Isnt it local council dependent?

That would be a tiny loo though, you’d have ten centimetres either side of your actual loo. About three inches. You’re basically going to have your arms pressed up against the wall when sitting on the loo. Are you sure that’s what you want?

We’re doing just this right now and ours is 780mm wide by 2 m. Drawings were Ok’d by building standards and the inspector has paid first visit, he was very happy.