40% payment within first 7 days of build starting

Dear Aktolman, it would be reasonable to have your builder prepare a payment schedule and a schedule of work on which you can track progress against payments. I would see no harm in your builder asking you for a deposit of between 10 to 20% of the final cost as there will be costs related to supplying materials to get the works started, after which it is a good rule for a job this size to have a 2 weekly valuation of the works. If you do not trust the builder and it seems dodgy, just get some more quotes in to compare his quote and generally be aware not to pay too much money. Ask your builder to give you a contract, generally a JCT minor works contract should suffice in this case, and appoint your architect, if you have one, to certify the works throughout the build if you are in doubt. If you do not have an architect, you might want to appoint one to do just this. This professional should usually be a member of the RIBA. Hope this helps, Enrico Garau

This is not the norm. A 10% deposit is usually acceptable but 40% is a piss take. Get him to draw up a payment schedule as part of a contract, if you are not happy with it find someone else.