Tackling rooftop vibration in modern developments
Rooftop plant can pose significant acoustic and vibration challenges, particularly when heavy mechanical equipment is installed above occupied commercial premises. At 25 Baker Street, a major mixed-use development in Marylebone delivered by Derwent London, this challenge formed part of a wider scheme combining office, retail and residential space in the heart of London’s West End. To address this, vibration isolation specialist Mason UK was appointed to design, supply and install a bespoke inertia base for a rooftop standby generator serving PIMCO Europe.
Working alongside principal contractor BW: Workplace Experts, Mason UK developed a solution centred around a concrete-filled inertia base supported on high-performance spring mounts.
Rooftop generators can introduce significant levels of structure-borne vibration, which can travel through the building frame and into occupied spaces if not properly controlled. In a mixed-use development such as 25 Baker Street, this can impact both occupant comfort and the performance of sensitive environments.
Inertia bases add mass and stability beneath mechanical equipment, helping to control movement and reduce vibration. When combined with spring isolation, they allow plant to operate on a “floating” system, significantly limiting the transfer of vibration into the building structure.
Mason UK designed the system at 25 Baker Street to not only support the weight of the standby generator but also align with the roof’s structural hard points and the constraints of a fixed crane-lift installation. Therefore, careful coordination was needed to ensure the base could be delivered, lifted and installed within a tight programme.
Design and installation
The inertia base was designed, fabricated and delivered to meet a fixed crane-lift deadline, before being lifted into position on the roof and set down onto temporary support blocks.
Mason UK installed the spring mounts in conjunction with the base, fixing them to the building’s structural supports before the standby generator was lowered directly onto the inertia base. This staged installation allowed the team to position the system safely while enabling follow-up works to be completed on schedule.
Isolation design
The system incorporates Mason’s SLR restrained spring mounts, designed with housings to allow safe access to all adjusting points while maintaining stability during operation. Each mount uses high-deflection springs, with a minimum deflection of 50 mm, in line with the project’s acoustic requirements, specified by Applied Acoustic Design.
Higher spring deflection results in a lower natural frequency, which is key to achieving effective vibration isolation. By reducing the system’s natural frequency, the mounts isolate both the generator’s operating frequency and any vibration associated with the supporting structure.
This is particularly important for rooftop plant, where vibration can otherwise travel through structural elements and into occupied spaces below. Therefore, Mason UK recommended a system that would help protect occupant comfort while maintaining the performance of critical building services.
Final commissioning
With the inertia base and generator in position, the system was initially supported on temporary blocks, with the spring mounts installed but not yet carrying the load. This allowed the system’s entire operational weight to be applied before the springs were finally adjusted.
Mason UK subsequently returned to site to complete the commissioning process, carefully winding down each of the eight spring mounts. As the adjustment bolts were tightened, the springs began to compress under the load, gradually transferring the weight of the inertia base and generator from the temporary supports onto the mounts.
As the process continued, the inertia base incrementally lifted clear of the support blocks. Once the load was fully transferred, the blocks were released, leaving the entire assembly supported solely on the spring mounts.
With the springs set, the system now operates as a fully floating installation, effectively isolating the standby generator from the building structure and minimising vibration transmission throughout the development.
To see more examples of how Mason UK can support vibration isolation across a range of applications, visit the case studies section of the company’s website https://www.mason-uk.co.uk/mason-uk-projects/
