mansard loft extension cost in east london

[iamnotstressed]

will be about 40sqm, we can borrow maximum of fifty grand and we want a no frills box, no bathroom, etc what do you think?

I think that's probably just about do-able. We're just about finished a loft conversion now and it will have cost about £60,000, but ours isn't the box type and has a bathroom, and some other bells and whistles. That also includes some unanticipated work like new doors to practically every room in the house to meet fire regulations. But it might be tight so you'd have to make sure your contract with builders was watertight on extra costs.

Scaffolding alone costs £6k so get quotes with that included. VAT and skips as well. It will be tight

sorry i am such an idiot, it's going to be a 20sqm loft extension, not 40!

We paid around £70k for reufrbishment (living room+hall way) and loft - it was the same around 20 sqm but with bathroom. But the best for you just to call to building companies, ours Werner and Werner Ltd gave us free quote after the guy came and saw the property and range of works. So you will have an idea of how much you will spend on your project. Check their website: www.wernerandwerner.co.uk/loft-conversions1.html
Good luck!

If you need steel supports that adds in a lot too. Ask a structural engineer not an architect or builder.