The Leeds-based group said Big Ben is now shrouded in scaffolding and Renew's team is working on the restoration and inner workings.
The group has also secured additional work on the Cast Iron Roof Restoration programme at the World Heritage site.
Chief executive Paul Scott said: "We've got the roof in South Yorkshire and we are employing people there to do clever engineering."
He was speaking as the firm announced a 1 per cent slip in revenue to £541.5m in the six months to September 30.
The group saw growth in engineering services, despite an anticipated reduction in rail revenue and a reduction in specialist building revenue.
The firm reported strong growth in its order book which stood at £558m, up from £511m last year.
In May, the firm bought QTS, a provider of specialist services to the rail industry which include civil engineering, geotechnical services, fencing and de-vegetation.
QTS has a longstanding relationship with Network Rail and during 2018 it broadened its framework positions, extending geographical coverage.
Mr Scott said: "We are delighted with the contribution from QTS. We've already got some synergies, some collaboration. It's really encouraging and it's a really good result for us."
Renew said its focus on non-discretionary UK infrastructure markets has Brexit-proofed the firm.
The group has also focused on recruiting British people so it isn't hit by an exodus of EU nationals.
"We've chosen to develop our own skills and we have over 220 people in apprenticeship programmes," said Mr Scott.
"We've invested heavily in the development of our people."