Private Highly Commended 2015
Architect: Wilkinson King Architects
Structural Engineer: Packman Lucas
Main Contractor/Builder: Westridge Construction Ltd
CLT Engineer: Price & Myers
CLT Manufacturer: KLH UK Ltd
Joinery: S M Carpentry Ltd (external: cladding & decking, internal: linings, timber stair)
Wood Supplier: Vincent Timber
Wood Species: Spruce, Western Red Cedar (Canada), Engineered Oak
The brief was for a timber building that would sit well within the rural setting overlooking the South Downs in Sussex. 143 CLT panels form the entire super structure, walls and roof, of the first floor. Mimicking the distant hills, the roof is designed to be an undulating surface, formed from a series of 28 triangular pieces. The roof and floors are entirely self-supporting. The CNC cutting technologies of the CLT production result in excellent dimensional stability, this has allowed for the panels to be shaped and the edges chamfered so they come together forming a continuous soffit with no visible joints. The wall panels are made of 3 layers of solid spruce boards 94mm overall and the roof panels are 145mm thick and made up of 5 layers. These spruce panels are also the finished surface of the interiors, giving a warm and tactile quality to the bedrooms and circulation spaces. The timber has been treated with a transparent white lacquer to prevent it yellowing over time. The use of CLT meant that this element of the design was built within ten days. The solid timber acts as a heat sink evening out the internal temperature and also the moisture content of the air. The stair, from basement to first floor, is formed using a metal frame and clad using spruce to match the CLT panels. The treads are open and cantilevered in order to make the stair as transparent as possible.
The entire first floor is clad using Western red cedar. The untreated cedar ages over a short period of time to become silver, matching the bark on the trees surrounding the building. The best visual grade of cedar was selected to avoid knots. It is tongue and grooved and fixed horizontally in 2.4m lengths, stacked one above the other. There is a 10mm gap between the boards giving a rhythm to the facades and allow for expansion and allow easy maintenance as necessary. The boards are nailed to tanalised battens using Stainless steel annular ring nails. The facade was very carefully detailed to avoid any protruding elements such as windowsills, which would cause staining to the timber as a result of water run off. The timber is used as a rain screen with a waterproof layer behind it. The windows and louvered shutters are designed to slide behind the timber cladding. Inside, European oak engineered floorboards are used in the first floor circulation spaces and office.
Further Sustainability Information: All the timber is FSC/PEFC/CSA/SFI certified. The KLH structural timber is highly sustainable. 1m3 (480-500kg/m3) of KLH panels will remove approximately 0.8 tonnes of CO2. 1m3 of KLH panels will have approximately 240-250kg of ‘lock-in’carbon. The adhesive used in the cross-lamination process is completely solvent and formaldehyde free (‘o’ class emission class). and KLH Massivholz has a zero-waste policy, whereby sawdust, shavings etc are reconstituted into biomass pellets and are used to heat/power the factory. KLH Massivholz is ISO14001 accredited.