The young John attended the Holy Ghost School, Basingstoke, of which his father was headmaster. He was then apprenticed to the royal carpenter, Matthew Bancks, whose niece he married, and lived for a while at Hampton Court Palace.
Among several buildings in and around Twickenham, John James designed the nave of St Mary's Church after it collapsed in 1713. Slightly further afield, he was responsible for recasing the tower of St Alfege's Church in Greenwich, London after it became unsafe (the tower was the only remaining part of an older church, the rest having also collapsed and been replaced by a new church designed (c.1714) by Nicholas Hawksmoor).