Mason UK were awarded the contract from the Maybourne Hotel Group to supply a variety of different noise and vibration isolation solutions for the prestigious Berkeley Hotel in Knightsbridge. This included elements in both the renovation of the existing hotel building and the brand-new extension known as “The Emory”. This article describes the challenges encountered in meeting an onerous specification.
Mason UK’s remit included the supply of several bespoke building isolation bearings, the design and supply of floating floor solutions, and the supply of acoustic hangers and other resilient products for “box in box” structures. The primary goal of the project was to isolate against ground-borne vibration, primarily from the nearby Piccadilly Line that runs just a few metres to the north of the site, as well as to provide the required level of noise isolation within each guest room.
Reflecting on the challenges of the project, Eleanora Bressi, Architectural Director with the Maybourne Hotel Group, recalled that ‘‘the biggest challenge was to have a building without noise because it’s a hotel, so you can imagine the performance specification is rather stringent in terms of acoustics.’’ At the basement levels, Mason UK were working to achieve a ‘‘silent spa’’ which is ‘‘almost impossible.’’
The isolation for the new block was tackled with two complimentary solutions; box-in-box construction for the ground floor and basement levels, with the rest of the 5000 tonne structure from first floor and above supported on bespoke spring bearings designed to have a natural frequency of 3.0Hz or less, as specified by acoustic consultant WSP.
The spring bearings are designed to last the life of the building, without the need for replacement, to provide certainty to the end client. They were also designed to accept the substantial wind loading without the need for supplementary restraints, which would have compromised the high levels of vibration isolation.
The steel frame was designed to very fine tolerances and Mason UK were able to match the required level of precision and provide custom spring bearing packs to support the entire building from ground floor upwards, working with the architect to locate the bearings within recesses in the ground floor to allow a clean finish around the columns.
Pre-compressed spring bearings were designed to release at seventy percent of the final load advised by WSP, who were also the structural engineering consultants for the project. This required careful coordination with the architect, structural engineer and steel frame contractor.
The box-in-box elements for the new block consisted of 100mm concrete floating floors for the ground floor, and three basement levels B1, B2 and B3, covering virtually the entire footprint of the building at each level. The floors for the basement levels were designed to accept a steel frame and inner box walls constructed on top of the floating floor.
Floating floors at the basement levels
For the first two basement levels B1 and B2, the FSN LDS Jack Up Rubber system with a natural frequency of circa 8 to 10Hz was required. For B3, which was the closest floor in level to the nearby Piccadilly Line, the Mason FS Helical Spring Jack Up system with a natural frequency of sub 4Hz was needed, due to being physically closer to the source of ground borne vibration.
As part of the specification process, Mason UK assisted in the construction of a test floor designed to simulate the final build and ascertain what level of performance could be achieved. The tests proved successful and a useful experience for the principal contractor to understand some of the specific requirements of a box-in-box construction, which Mason UK were able to provide valuable guidance on to ensure the strict demands of the project were met.
On each level, extra jacks were incorporated into the design to account for the point loads imparted by the internal steel frame. The design for each floor was carefully coordinated with the structural engineer, architect, and contractor to account for all internal wall loads, finishes and floor penetrations.
Due to the construction sequencing of the project, the floor for each level had to be cast and jacked while the tower crane was still in place. Working around this complication, Mason UK designed the infills areas to seamlessly integrate with the main jack up floor slabs on each level, ensuring consistent performance across all areas.
Floating floors and acoustic ceilings for hotel rooms
As part of the renovation of the existing block of the hotel, Mason UK worked with the contractor on site to design and supervise the installation of floating floors for the hotel rooms from levels one to eight. Due to structural limitations and logistical restrictions within the existing building, a dry system was specified. The system proposed consisted of several layers of cement particle board supported on Mason EAFM isolators, with a natural frequency of circa 8 to 10 Hz.
To facilitate this, Mason UK worked closely with the contractor undertaking the work to provide design and on-site assistance, to ensure the highest possible quality installation, and to catch and rectify any issues as soon as they occurred.
In addition to the floating floors, each level required a low-profile but very high-performance acoustic ceiling system to ensure the high level of noise isolation required for a luxury hotel. To this end, Mason UK worked with the architect and contractor to design isolated ceilings suspended from Mason HD-B rubber ceiling hangers supporting a grid of Unistrut and a heavy build-up of several layers of cement particle board and dense plasterboard. As with the floors, engineers regularly attended site to oversee the installation and ensure the highest possible level of quality and performance.
Things don’t always go to plan on site, so having a partner that can offer flexibility has also been important. Considering the relationship with Mason UK, Eleanora commented that ‘‘they have been making a tremendous effort. I have learned so much about acoustics. They basically pulled the project together.’’
Providing acoustic solutions for hotels can be especially challenging, especially if the hotel in question is so close to a major tube line. However, for a luxury hotel like the Berkeley Hotel, there is no room for compromise and things have to be right. A high-profile project like this is challenging and highly specified, making quality and acoustic performance prime requisites. A successful outcome necessitates working with the whole design team, from the architects, structural and acoustic consultants, to the main contractors and subcontractors.