Hopes of a round of consolidation among UK housebuilders have driven shares in the sector higher.
Reports suggest the bid for Westbury could be worth £638m
Westbury led the surge as investors got their first chance to trade in its shares since a takeover approach from Persimmon on Friday.
A tie-up would see the two overtake Barratt Developments as the UK's largest housebuilder by sales volume.
However, analysts have speculated that Persimmon could face competition from rivals in a battle for Westbury.
There was also talk of other firms in the sector becoming targets for takeovers or mergers.
"We wouldn't rule out some of the smaller players in a tie up such as Redrow and Bellway or Bovis and the larger players that may look vulnerable are Wilson Bowden and Taylor Woodrow," said Tessa Guy, and analyst at Seymour Pierce.
While Persimmon has yet to reveal the details of its offer, reports suggest the York-based group is willing to pay 560p a share - valuing Westbury at £638m.
Shares in Cheltenham-based Westbury ended up 12.7% at 556.5p while Persimmon rose 9.7% to 1042p.
Elsewhere, smaller rival Redrow increased 4.3% to 485p, Wimpey Homes moved up 1% to 438.75p and Barratt Developments rose 2.3% to 863.5p.