Any ideas on flat roof extensions (extra floor)?

[user1473767408]

Our house is a 60s townhouse with a flat roof. Wondering if there's a point in extending upwards, and build an extra floor. At the moment there's the ground floor and two more ( so it's a three-storey house I guess).

The building is a simple box construction, and we could do with another room (at least) and an ensuite. Has anybody done that or have any suggestions? I think there may be prefab options, but they're probably more expensive, on the other hand if we go for onsite building we would be knee-deep in dust for months! We'd love some more room, and also altering the flat roof that tends to need replacing every 10-15 years thanks to rain.

What would you do? Ideally, what have you done?

You'll definitely need planning permission as the change is visible from the front, so I would speak to your local planning department to see whether there is any precedent.

I wonder whether a butterfly loft conversion would work on this type of building?

www.southlondonlofts.co.uk/YourHome/flats-london-roof.html

sorry I think they are actually called Mansard roof extensions

Thank you LittlePickleHead, that's very helpful!