Burt's father was a stone merchant, and his mother was the sister-in-law of John Mowlem, a struggling workman in London at the time of Burt's birth. Like his uncle, Burt worked in the quarries around Swanage.
Burt moved to London to join Mowlem's business, becoming a partner in 1844, and managing the business after Mowlem's semi-retirement the following year. He married Elizabeth Hudson in 1841, and the couple had six children. On taking over the Mowlem company, Burt substantially expanded the firm's operations. Surviving the lean years during the financial crisis of 1866-7, his company became a major public-works contractor and won the contract for Queen Victoria Street in the City of London (1869), followed by Billingsgate Market (1874-7), and the City of London School in 1880 on the new Victoria Embankment, amongst others.
Burt also, like his uncle, maintained an interest in Swanage, establishing gas and waterworks, developing the Durlston estate, and lived in a large house called "Purbeck House", now a hotel, on the main street. He and his wife bought the house for £550 and lived in it for 17 years. The porch is made of white Cornish granite, the mosaic floor is copied from the pavement in Queen Victoria Street, London and some of the tiles are from the Palace of Westminster. The Swanage suburb of Durlston was largely developed by Burt, who also laid out Durlston Country Park.
Many architecturally interesting buildings and monuments were scavenged as a result of the company's construction work on prestigious projects in London, and re-erected by Burt in Swanage and Durlston. The 1670 porch for the Mercers' Hall now adorns Swanage town hall, and a clock tower commemorating the Duke of Wellington which once stood at the end of London Bridge is now a feature of Swanage seafront. More prosaically, many of Swanage's cast iron bollards were originally made for London boroughs, and still carry their names.
George Burt was buried at Kensal Green Cemetery. Control of the company passed to his descendants Sir John Mowlem Burt (1845-1918) and Sir George Mowlem Burt (1884-1964).