Taylor Wimpey's chairman Norman Askew has said he will leave the board of the housebuilder by the end of December 2010.Askew, also chairman of engineer, IMI, has been chairman of Taylor Woodrow since July 2003 and continued his role when the company merged with Wimpey in July 2007.A process to recruit a successor is already underway."We have come through unprecedented market conditions since the merger. It is important that as we enter 2010, we continue to proactively manage our business in what are still uncertain times," Askew said.Meanwhile, non-executive director David Williams has said he'll leave the group at the end of March next year after his recently announced appointment as joint chairman of paper and packaging company Mondi.