Top-floor areas have been closed at County Hall in Worcester where the roof has potentially dangerous concrete.
County council chief executive Paul Robinson said he had been made aware the venue had reinforced autoclaved aerated concrete (Raac).
The top floors of each pavilion, the area around the council chamber and parts of the atrium area needed to be vacated temporarily, he stated.
He added there were plans to ensure service delivery could continue.
Raac is a lightweight concrete that was used in roofs, floors and walls between the 1950s and 1990s, but as it is aerated, it is not as durable and therefore only has a limited lifespan.
Buildings with the substance were marked potentially dangerous when earlier this summer a Raac beam at a school collapsed, prompting closures nationwide while safety checks were carried out.
