What is a London Roof?

[Wyn]

I’ve just been reading a surveyors report that describes the property in question as “of late Victorian construction with solid brick walls and a London roof”
Despite living in London all my life I’ve never heard this architectural term before :confused:
Looking at the corresponding photograph it seems to be a flat roof. Would a similar roof outside the capital still be called a London roof?

[lang rabbie]

The roof is usually hidden by a front parapet, and has two separate shallow slopes - they can often look almost flat from the back. The two parts of the roof (which may be covered either in slate or lead/felt if very shallow) slope down from the party walls to a "valley gutter" running along the centre of the house parallel to the party walls, and feeding into a rainwater hopper in the middle of the back wall.

They're sometimes known a a "butterfly roof". They are common in Georgian/early Victorian terraces with party walls separating the houses.

Almost every surveyor will include some sort of disclaimer like this one.

Valley Gutter
A very common problem with this type of roof is the central valley gutter
which more often than not leaks. We are concerned that this is a liability that you will have to take on as well.
ACTION REQUIRED: We would very strongly recommend that the
landlords are contacted by your solicitor to confirm what recent work
has been carried out to the roofs and when they anticipate they will need replacement as this will be a very costly exercise.

[Mrs Magpie]

Oooh, I wondered if that might be the case, glad to know my supposition was correct :)

[lang rabbie]

A more succinct definition than mine:

A traditional London roof form where the roof is constructed in the form of a ‘V’ and where the central gutter is at right angles to the front raised parapet, which hides the roof. This roof has no ridgeline as the party walls rise above the highest part of the roof. This form is often expressed at the rear of the property as a ‘V’ shaped butterfly parapet.

[Wyn]

Ah, v. interesting. Thanks for the response Rabbie :)
I work on the fourth floor and my office conveniently overlooks some period properties. I’d never really noticed before, but they are just as you describe them – from ground level you can only really see the façade and I’d always assumed these were flat roofs.
So can I assume they are peculiar to London?

[liberty]

You learn something new everyday