The joys of working with Cross Laminated Solid Timber – A changing mind set…

The joys of working with Cross Laminated Solid Timber – A changing mind set…

Modern timber construction in the U.K. has been viewed with suspicion for many years having suffered adverse publicity over issues which have occurred mainly in the domestic market. Therefore it was not easy to convince a client to break with the convention of utilising concrete, steel and masonry in a commercial application, and adopt the unfamiliar and relatively new (for the U.K.) construction system of Cross Laminated Solid Timber.

The new International Teaching facility and Administration block at the John Innes Centre in Norwich, England, does just that. A new Cross Laminated Solid Timber (CLST) frame has been cleverly inserted into the shell of 3 existing single storey redundant brick buildings (which had to be retained for financial reasons).

The brief called for a sustainable solution to accommodate a number of uses, including a post graduate teaching facility (including Computer Lab Auditorium, Wet Laboratory and Ideas Lounge), a Computer Data Hub, and Administrative Offices.  A tight deadline also required a rapid construction method.

The CLST single storey superstructure fits within the 75m long x 17m wide existing footprint and spans off the existing brick walls on to a new central CLST core. Accommodation is arranged around a central double height atrium, which extends longitudinally at roof level to conceal all the plant services.

The design benefits from a number of sustainable features. A sedum roof helps to regulate the thermal performance of the building (the Data Hub produces more heat than the building requires to heat it), and also provides an interesting roof scene for the neighbouring buildings. A wrap around timber louvred sun visor was designed to regulate solar gain to the south and west, while the existing hotchpotch brick external walls have been over clad in a profiled steel envelope (chosen for its recyclability). Other sustainable features include a natural ventilation system www.breathingbuildings.com and use of untreated borehole water for WC flushing. The final building attained a BREEAM Excellent rating. www.breeam.org/page.jsp?id=66

CLST is fabricated by bonding together timber boards with structural adhesives to produce a solid timber panel with each layer of the panel alternating between longitudinal and transverse lamellae. Alternating the grain directions of each layer of timber reduces many of the weakness that previous timber products had, vastly reducing the effects of shrinkage and swelling, and enables loads to be transferred in more than one direction.

The Benefits of CLST:

Locks in carbon
Prefabrication minimises waste, and speeds up construction on site
Negates the need for internal surface treatments
Helps to regulate internal humidity and comfort levels
Dry Construction is not dependent on weather conditions
Has superior fire resistance properties over other timber products
Has inherent noise absorbing properties
Is able to absorb a large amount of heat energy
The use of simple junctions minimises the interface of trades on site
Easily demounted and recycled when the building has come to the end of its life

Architecturally

CLST gives a minimal simplicity to a space, a homogeneous feel as if the whole building has been hewn out of a monolithic block of material, a ‘pure shell’ for the fittings and furnishings to be displayed within. Prefabrication dictates thinking where everything goes from the outset, including such things as the position of service runs and electrical sockets and switches etc., thus reducing the risk of unforeseen on-site surprises. It therefore has a greater potential for delivering a holistic building. Time invested upfront however is recouped by the significant reduction in time spent during construction.

From a design point of view it’s like constructing a card model at full scale which seems to retain a pureness of the original design concept. It provides a blank backdrop onto which colour can be dropped and lends itself brilliantly to the minimalist aesthetic.

Aesthetically

Omitting the need for internal finishes, the CLST shell retains the quality and feel of the ‘raw’ material and contrasts the industrial and refined with the softness and delicacy, of the internal finishes of carpets and furniture. It also helps to visually unify the different elements of a multi-use building.

Mart Barrass  RIBA

Posted on: 1st May 2012.