Project Overview:
Background:
Premier Inn London Docklands is a popular waterfront hotel overlooking the Royal Victoria Dock and set close to the ExCeL Centre and London City Airport. It is a seven-storey building that features balconies and brise soleil sunshades. The ground floor and first floor walls are of blockwork masonry construction up to a transfer slab, above which the walls are of timber frame construction. The ground floor walls are externally clad with facing brickwork, and above this the walls had an external insulation system with a render finish.
Due to movement of the timber frame, some areas of the render had buckled and cracked, resulting in localised water ingress. The owner therefore commissioned a replacement cladding project.
The Brief:
The brief required that the replacement external wall insulation system should employ non-combustible mineral fibre insulation, carry appropriate certification, and be able to replicate the colours and appearance of the original design. The new system should also be designed so that future movement within the timber frame could be accommodated by the system.
The Design Stage:
Axiom Architects selected PermaRock Products as their preferred EWI system supplier for the scheme, and PermaRock Technical Services staff immediately began discussions with Architect and main contractor to agree designs, detailing and timescales for delivery.
Further design work was required once the failed insulation system was removed. The work revealed that water ingress had led to localised problems including swelling timbers and, in addition, some of the original concrete blockwork was found to be structurally unsound. It was evident that the first-floor walls would require extensive brick and blockwork repairs.
This demanded the installation of heavy structural steel to make the façade sufficiently strong to resist wind loads and to support the weight of the external wall insulation system without causing any structural issues behind the system. However, the heavy-duty steel frame reinforcement projected almost 80 mm from the main façade.
In order to enclose the frames within the EWI system, to maintain a flat façade and to meet other practical demands upon the system (such as robustness, safe fixing, etc.) it was necessary to increase the thickness of the insulation boards. The thicker insulation enabled the projecting steel framing to be incorporated into rebates cut into the back of the insulation. Thus, PermaRock needed to design systems of different thicknesses, and to perform U-value calculations and thermal bridging calculations for all the various permutations. Over and above this, additional design work was required to accommodate the movement joints, some of which coincided with room vents and the fixings for brise soleil sunshades.
Specification and System:
PermaRock’s Mineral Fibre EWI System was chosen to provide the thermal insulation for the building. It is suitable for application onto all building types, including multi-storey residential blocks where the non-combustibility requirements of the Building Regulations need to be met. It features non-combustible (Euroclass A1) mineral fibre insulation boards and is compatible with a range of renders and decorative finishes.
The facing brickwork of the ground floor walls required no retrofit work and was left untreated. For the walls up to 6th floor level, contractors installed 80 mm and 110 mm mineral fibre insulation. The walls of the top floor, set back from the main facades, were treated with 50 mm mineral fibre insulation.
The chosen finish was PermaRock’s self-cleaning SiliconeUltra K-Finish with a 1.5 mm grain size and ‘stippled’ texture, supplied in two special colours. On the top floor, the colour was Cameo 135 (applied to 400 m2 of walls) and on the 1600 m2 of walls beneath, the chosen colour was Lazur 60. The use of these colours and the 1.5 mm aggregate render ensured that the appearance of the finished project closely matched the hotel’s original design.
SiliconeUltra K Finish is lightweight, water-repellent and demonstrates excellent water vapour permeability. It is through-coloured and resists the accumulation of dirt, so it tends to retain a clean, bright appearance even in challenging urban environments. Similarly, an anti-microbial preservative helps to resist the growth of unsightly moss and algae. It is available in an extensive range of colours and a choice of textures and grain sizes: 1.5mm, 2.0mm and 3.0mm.
Performance: Fire Safety
PermaRock SiliconeUltra K Finish is assessed to EN 13501-1 and when used in conjunction with PermaRock Mineral Fibre External Wall Insulation the resulting system achieves an A2-s1,d0 Reaction to Fire classification and is suitable for use on buildings of any building height, including ‘relevant’ buildings, without height restriction.
The complete system used on this scheme has been independently tested (BRE Certificate 158/12) and has an assessed lifetime of at least 30 years. It exhibits excellent resistance to wind-loading, and is among a small number of systems to be supported by a SWIGA 25-year guarantee.
Performance: Thermal Insulation
Calculations showed that the new PermaRock system provided U-values below 0.3 W/m²K in line with the project brief.
Other Issues:
During the scheme, the installer faced an unexpected challenge. Unrelated civil engineering works at the nearby ExCeL Centre caused a rupture in the mains water system and this, in turn, led to localised flooding. Contractors arrived to find the site compound under two feet of water, which had caused damage to some insulation boards and stocks of base coat. Having preserved what it could, the installer quickly ordered new stock and, as a UK-based manufacture with nationwide delivery capability, PermaRock was able to replace the materials quickly, thereby minimising risks of project delays.
Result:
The objective was to install a fire safe, durable and hard-wearing system with properly designed movement joints, while also preserving the original appearance of the building, and either matching or improving upon the performance of the system that had been removed. In the event, all those objectives were achieved.