The University is expanding its Faculties of Engineering and Physical Sciences and Health and Medical Sciences at its Stag Hill Campus in Guildford.
Oringinally the three-floor build, which was structurally engineered by BDP, was expected to cost around £5.3m. But industry inflation has pushed up the cost.
But Gilbert-Ash finally secured the 25,000 sq ft design and build job with a bid of £8.25m, against fellow Northern Ireland firm McLaughlin & Harvey, local builder Beard Guildford and Galliford Try.
Work is expected to start on the new science, technology, engineering and mathematics building next month, which will accommodate laboratories, teaching space, offices and seminar rooms.