Barratt Developments said momentum is continuing to build and with forward sales up substantially, it is confident it can improve its performance further still in the year ahead.In an update for the year ended June 30th ahead of its annual results in September, the house-builder said profit before tax and exceptional items for the full year is expected to be around £192m, ahead of the top end of analysts' expectations.The sales rate was up 17.9% in the second half on the prior year, with average net private reservations per active site per week of 0.66. Sales rate has increased 34.7% since the launch of Help to Buy in April.Private average selling price climbed 9% in the second half on the prior year to £221,000, reflecting changes in mix. The operating margin is expected to increase to 10.4% in the second half and 9.7% for the full year, up from 8.2% in the prior full year.Barrat said strong momentum is expected with total forward sales up 53.6% to £829.7m as at June 30th. Chief Executive Mark Clare commented: "As more house buyers return to the market, supported by improved mortgage availability and the Help to Buy scheme, we are in a strong position to continue to grow the value of the business.""We are increasing our investment in land whilst reducing debt and have delivered a performance ahead of expectations."The group's net debt position as at June 30th reduced to £30m from £167.7m the year before.