Any body know rough costings for "converting" a flat roof to a pitched roof?

I know there's loads of variables, but if we accept the current foundation and walls can support it.

New pitch would be in line with original house, which is akin to a chalet bungalow, flat roof size is roughly 9.5m by 6.5m. The current gable end is the 9.5m length.

 

How would this cost to making the new roof area live-able?

so you want to make a flat roof into a pitched roof with habitable space in it? (is it a garage?) sounds like a decent footprint but it's a massively open ended question you ask here! (iirc I did a loft over a garage that worked out at somewhere around 1k per m2 by the finish but that was new build on top of nice new walls - and the client did nothing, all done by main contractor)

I appreciate it's a massively open question.

 

It's a house we're trying to arrange a viewing for. Looking at pictures of earial views below can be made out.

The flat roof extension isn't actually flat, even for flat roof standards.
Almost half of it has a raised portion, internally one has to go up some stairs to gain access to a room and shower room. The slope of the flat roof is down the 9.5m length, which starts at the same height as the raised part before ending (externally) at the same height of the originial pitched roof.
The house is on a hill and looking at proportions they've converted a single garage (the raised part) into rooms and then added the flat roof extension in-filling between it and the originial house, but kept that at house level while "old garage" was up the hill. To further complicate matters, there's also a double garage thats flat roof at same out of the raised portion and a further "extension" off the main space also a flat roof, both are off-set to this main space making it pointless to incorporate.

Describing all this makes one think it may be easier to just knock down the main flat roof space and start again so internals are level.

Changing from flat to pitched would need planning permission.

1 hour ago, Temp said:

Changing from flat to pitched would need planning permission.

I think that would be obviously expected and wasn't part of the original question.

Budget £1,500 per metre.  Should be accurate within a factor of 1.5.