Mears has been selected as preferred bidder for a £300m repairs and maintenance contract by housing association Family Mosaic.
The 10-year contract covers more than 20,000 homes in London and the Home Counties and is expected to commence in October 2010.
Mears will provide a 24-hour call centre service for all tenants of Family Mosaic and be responsible for responsive, void, gas maintenance, property surveying and estates management services.
Bob Holt, chairman of Mears, said: "We have been working on behalf of Family Mosaic since 2004. This award represents the biggest contract award in Mears' history."
"Mears social housing bid pipeline for contract tenders is in excess of £3 billion and we continue to target customers who share our view of long term partnering arrangements."