Willmott Dixon has won a five-year UK prisons contract that could bring in up to £60m of work.
It was chosen by the National Offender Management Service to carry out the new-build and refurbishment programme.
It will start on a 180-place house block at HMP Swaleside in Kent early next year and will also work on a £35m project at HMP Nottingham for a 510-place housing block.
Construction is due to start in November next year.
Inspace, Willmott Dixon’s demerged housing arm, has won a £15m housing repairs contract from Hinckley and Bosworth council in Leicestershire.