What plans do I need for builders to quote for my extension?

The building regs drawings are sufficient to be given for quotes. Your architect may be submitting a full plans building regs application in which case I would suggest waiting until this has also been passed just in case the inspectors have any recommendations. This will ensure that any quotes you receive are as accurate as possible and will help prevent any hidden 'extras' (providing the builder knows what they are doing!). Although if he is submitting a building notice there is no reason why you can't start to get quotes now. Keep a contingency budget aside though as things like the groundwork stage can sometimes reveal a few surprises even the best plan drawers weren't aware of. Louise UK Property Services

Is your Architect preparing a Schedule Of Works for the job? I usually do if I can't get it all on the Build Reg drawings.