Britain's biggest supplier of building materials Travis Perkins announced the resignation of its Chief Executive Officer (CEO) as it reported a 4.1 per cent rise in first-half profit.Geoff Copper, who has been CEO since 2005, will step down on January 1st and as a Director on March 6th. Current Deputy Chief Executive, John Carter, will take over the reigns.The firm posted an underlying pre-tax profit of £136.1m for the six months to the end of June, boosted by a 1.6% rise in revenue to £2.45bn.The company said it proved resilient against challenging market conditions and cold weather which hurt construction industry activity in the first quarter.As the weather improved in the second quarter so did the sector and the group's sales. Travis Perkins increased its interim dividend 25% to 10p per share.Cash generated in the first half reduced net debt by a further £46m to £406m at the end of the period. Adjusted free cash flow for the period was £116m, up from the prior year's £99m. The group forecast full-year earnings per share in line with analysts' consensus forecast of around 100p.Shares fell 1.11% to 1,691p at 10:35 on Thursday.RD