Devon & Somerset Fire & Rescue freed both men from the rubble after an internal collapse in the landing area of the building.
The Western Gazette said the site was run by Brookvale Homes on behalf of Yarlington Housing Group.
A man in his early 20s has been flown to Frenchay Hospital by air ambulance after suffering head and leg injuries.
A second casualty, in his 60s, who had a small cut to his head and ankle injuries has been taken to Yeovil District Hospital.
The fire service said: “Two fire appliances and a Rescue Tender from Yeovil, the Special Rescue Team from Bridgwater and various heavy rescue modules from the Urban Search and Rescue Team were sent to a report of a building collapsed at the above location.
“On arrival crews confirmed that a building under construction had suffered collapse.
“Fire crews assisting ambulance paramedics in the removal of two injured casualties.
“One of the casualties was taken to hospital by land ambulance and the other casualty taken to hospital by air ambulance. The area was cordoned off.”
