A company insider said Wimpey would close the office despite deciding to keep the Laing brand and run it as a separate division.
The source said: "It is fair to say that the Milton Keynes head office won't be needed. Laing Homes will be organised like Wimpey regions." Wimpey has comparatively autonomous regions compared with most other housebuilders.
Wimpey has not said how many jobs will be lost after the tie-up but expects the integration of Laing to cost £7m, mainly in redundancy payments. The housebuilder expects to save £8m a year after eliminating duplication, and another £2m from better deals from suppliers.
The deal, which will make Wimpey the UK's largest housebuilder, was announced last Wednesday after months of speculation. It will give Wimpey access to the lucrative South-east market as well as increasing its average selling price, both of goals of Wimpey chief executive Peter Johnson.
Laing's average selling price for the year to 31 December is expected to be £280,000 – almost twice as high as Wimpey's.
The Wimpey source said the purchase of Laing had speeded up the group's growth strategy. He said: "We could have built that kind of operation up organically, but it would have taken us five years."
As expected, Laing Homes' managing director Steve Lidgate will leave the business after the deal goes through later this year. His departure became certain after he led an unsuccessful management bid for the business.
An analyst said: "Steve was very keen on buying the firm but evidently couldn't raise the cash like Wimpey could. Once that happened, he was always going to go." Industry sources predicted Lidgate would stay in the industry.
Wimpey said a managing director would be appointed and would report directly to the group's main board.
The City generally reacted positively to the deal, with Wimpey's share price staying static at 285p as most other housebuilders suffered falls. But analysts were concerned that Laing's margins fell during the six months to 30 June. Wimpey said this was because of rising overheads and constraints that the Laing group put on the division while it was up for sale.
Wimpey said Laing had underlying strengths and that it expected the housebuilder to lift performance now the deal was completed.