The Enquirer understands that Tarmac swooped after seeing rivals like FM Conway pick up a succession of road maintenance and surfacing contracts in the capital.
Tarmac is keen to break into the term maintenance market in the South East and Riney has a string of existing deals in the region including Tower Hamlets, Greenwich and Waltham Forest.
A Tarmac spokesperson said: “Tarmac will work with the JB Riney management team to maintain continuity for existing Riney customers.
“The company will continue to operate under the Riney name, and will form part of the Highways Services division within Tarmac’s Contracting business.
“Combining the expertise of both businesses in the London market strengthens Tarmac’s overall civils and highways customer offer, and builds upon its existing network of strategic sites, logistics and operations in the south.
“With over 40 years’ experience, Riney is one of the capital’s leading contractors.
“The business offers expertise in a number of specialisms, from term highways maintenance, to civil engineering, surfacing, street lighting, winter maintenance and utilities infrastructure.”
Latest accounts for Riney for the year to March 31 2016 show it made a pre-tax profit of £590,000 on a turnover of £42m and employed 253 staff.
One industry expert said: “This is big news in the highways sector and gives Tarmac a foothold in the term maintenance market where it can take up to five years to win contracts from a standing start.
“I’m sure Riney will now be bidding for a lot of work and will see this as an opportunity to grow the business exponentially.”