Whitney Tilson, the columnist and money manager who called the housing crash, is now betting on another downturn in the stock market.

Tilson, of T2 Partners, tells CNBC that “we’ve doubled our short book from 30% to 60% and we’ve trimmed our long book from 120%to about 90%.” His favorite short area: homebuilders.

Tilson, who has been warning that investors should cut back and be more defensive for a couple months now, says he thinks the economic recovery will be weak, and one factor driving stocks lower will be unemployment. He thinks the jobless rate will remain fairly high, which means mortgage and consumer loan defaults are going to surge. “There are probably going to be $700 billion of losses in total over the next 8 years and we’ve only seen a few billion of it because those loans haven’t reset,” he said.