Ripley was also involved in various speculative adventures, mainly in central London. In 1726 he was the original lessee of the west side of Grosvenor Square, and although his contribution there was limited to 16 Grosvenor Street he built a number of other houses in central London. Ripley was active in promoting the scheme to build Westminster Bridge and was also involved in Richard Holt's failed attempt to develop artificial stone. Nevertheless, he seems to have been an eager investor, being one of the few to make a fortune out of the South Sea Bubble.