The group is expected to have a turnover of £25 to £30 million and has a combined workforce of more than 200.
Novitas works across a variety of technical areas including mechanical and electrical services, refrigeration, air conditioning and ventilation.
The firms have experience on industrial, retail, commercial and public sector projects. Both companies felt merging provided them with the best growth strategy.
Grahame Preston, chairman of Watsons and now chief executive of Novitas said: “Naturally, both companies wanted to grow organically but we both recognised this would be difficult in our industry because it’s extremely hard to find highly skilled people.”
Bernard Davies, the managing director of Southern & Redfern, who becomes chairman of the group, added: “The new firm has a young, cutting-edge management team and we can look forward to a successful future and sustained growth.”