Harnett, who is the firm's managing director, said the company had picked up its first contracts. He said: "We have picked up instructions from as far north as north Yorkshire and as far south as Margate."
Harnett said that these contracts were less than £50,000. However, he said he will be seeking larger contracts.
Harnett is one of two directors of Buildingsfirst. The other is Kathy Layte, who was London regional surveying director at Capita until June.
Harnett was with the consultancy arm for 14 months. He had previously worked for property agent Colliers CRE.