Westbury's existing business performed well, with operating profit increasing from £35.7m to £42.4m on turnover up 12% to £295.8m.
Colin Cole, Westbury Homes' managing director, said demand for housing remained strong despite predictions of a market collapse. He said the Prowting integration might not end up costing the group as much as the initial estimate of £4.5m.
Prowting, which Westbury bought for £141m, contributed to the firm's results for 10 weeks. It had a pre-tax profit of £2.3m and sold 270 units over the six months to 31 August. Cole said 100 staff had been made redundant and three of its five regions closed.
Westbury expects to save £3m by integrating the two firms in the second half of the year, and £7m a year from 2003.
The group's prefabrication factory, Space4, lost £1.9m during the period and built 300 units. Cole said it would make a profit next year when production should top 2000 units.