A technical case study – the Metropolitan Hotel, London

Citation

(2001), "A technical case study – the Metropolitan Hotel, London", Facilities, Vol. 19 No. 3/4. https://doi.org/10.1108/f.2001.06919caf.002

A technical case study – the Metropolitan Hotel, London

A technical case study – the Metropolitan Hotel, London

Keywords Refurbishment, Maintenance, Roofing

The Met Bar at The Metropolitan Hotel is one of London's premier celebrity hang outs. They have very high standards for entry … "members" only!

Your name's not on the list … you're not coming in …

In the same way the specification for the refurbishment of this prestige hotel on Park Lane had to live up to these exacting standards. The ten storey Metropolitan Hotel stands on its prominent site with stunning views across Hyde Park. The refurbishment of the old Londonderry Hotel has given birth to an ultra modern world class hotel that pays great attention to detail. Even the staff wear Donna Karan commissioned uniforms …

There were many critical decisions made when the flat roof area was redesigned. As a world leading brand, the Styrofoam Solution, Roofmate LG rigid insulation board with integral ballast from Dow Construction Products was specified.

As a start point, the decision was made to retain the existing waterproof membrane, as is often the case with a refurbishment. This was performing well and the programme did not allow for its removal and relaying. This roof is approximately 900m². The improvement of the thermal performance was critical and as such 100mm Roofmate LG was specified.

The first design parameter was set an inverted or upside down roof (USD) was the only feasible solution. Dow developed this design over 20 years ago. There were key benefits with this choice. There were to be high levels of plant on the roof for the new air conditioning requirements of such a high quality hotel. In turn, these areas would require frequent access by maintenance personnel. A USD designed roof would protect the waterproof membrane from damage and give a defined area as walkway. In addition, the membrane would not be exposed to UV degradation and high temperature differences that can be experienced within each day and throughout the year. Due to the location of the site and its height, careful consideration was given to the means of securing the insulation.

Roofmate LG was chosen because the roof could accommodate an additional load of 25kg/m². Advice on its securement was provided by the Dow Technical Centre. In this case, parviors were added as additional ballast around the perimeter to counter the effect of wind uplift.

Wind uplift calculations are critical for a USD roof design. At Dow, this service is an integral part of the consultancy offered to designers and specifiers. The geographical location of the site, the building aspect and height are all key factors in the design that will dictate the ballast, the bonding and the pattern for the interlocking Roofmate LG boards.

The contractors, London & Home Counties Roofing, were very familiar with the benefits of USD roof applications. The main contractor, Komojo, also had experience of this Styrofoam Solution.

Due to a short programme and a congested site with all trades working with cross over times, product delivery times were critical as goods hoist times were rationed strictly. The distributor Solant Insulation Supplies London, worked closely with the installer to ensure timely delivery.

The comment from Alan Richardson, London & Home Counties Roofing, summarises the views of his company:

Using Roofmate LG was more expensive than an inverted system ballasted with paving slabs or gravel. But on a ten storey building the cost of lifting materials up to the roof would have been very high anyway, so it was economical. The ease of site handling was a real benefit to my team who had to work around the M&E contractor and every other trade under the sun that seemed to be up there with us!

There were other site specific issues that needed to be addressed. The vast expanses of glazing to the suites on the top floors needed to be balanced with high levels of insulation. The thermal conductivity for Roofmate LG is 0.028W/mk. The specification of 100mm of insulation was close to the limit for the height of the parapet walls to the roof perimeter (see Figures 7 and 8). If traditional ballast was employed the parapet would have needed to be raised. By using Roofmate LG, no alterations to the existing roof were necessary.

Figure 7 Redesign of roof on the Metropolitan Hotel, London

Figure 8 The Metropolitan Hotel, London

The ease with which the material was handled on site was a bonus, normal hand tools were all that were required for trimming and cutting boards around plant penetrations, skylights and upstands, plus all handrails and walkway balustrades. The boards were even carried by hand to the roof in the hotel goods lift!

For further information visit the Dow European Web site at: www.styrofoameurope.com and select the UK, or contact The Dow Technical Centre on +44 (0)20 8917 5049 or e-mail: styrofoam-uk@dow.com