25 King sets a global precedent for timber building. Timber high-rise and mid-rise has continued to push the boundaries for larger structures in terms of carbon sequestration and economic feasability. 25 King presents a confident nod in the right direction for mass timber consteruction pushing architects to think beyond concrete and steel commercial solutions.
Historically, in Australia, timber hasn’t often been considered for mid- to high-rise commercial buildings, due to the lack of internal walls to provide structural support. However, recent innovations in engineered timber meant that the unique 52 metre tall, 10-storey 25 King could be built.
Located in the heart of Brisbane’s RNA Showgrounds, the raw expression of the mass timber construction at 25 King St differentiates it from typical concrete and steel mid-scale office developments, and represents an impressive achievement in timber engineering .
A simple, 6x8 metre system of Glue-laminated beams and columns support a stack of cross laminated timber (CLT) floor plates. The timber stack is supplemented by timber core walls that support a flexible floor plan.
Major services are networked in specially designed zones so that each floor can easily accommodate different tenancies.
25 King is targeting a 6 Star Design and As Built V1.1 Green Star Rating, Well Platinum Core & Shell Rating and 5 Star NABERS Energy Base Building Rating. In order to acheive this ambitious goal, sustainable features reduce energy usage by 46% and water usage by 29%. These include
- Natural daylighting in the interior
- Efficient low-temperature HVAC and lighting systems
- Aluminium sunshades that reduce heat load
- Rainwater harvesting
- Improved indoor air quality
- Photovoltaics and metering and monitoring to limit wastage.
Biophilic design principles guided the building’s timber and natural materials palette as well as its layout. The office floors glow with the warmth of the timber columns, beams and floor soffit. The use of natural timber—as opposed to concrete, steel and plasterboard—better connects occupants with nature, fostering a happier and healthier workplace. The 6x8 column grid creates a more intimate scale on the floors. It also minimises the size of the Glulam columns, allowing them to register almost as joinery. Both aspects make the scale of the floors feel more manageable, improving the daily experience of the space.
25 King’s materials and construction techniques model timber building best practices, which were achieved by rethinking traditional project delivery practices and timber’s inherent structural limits.
Lendlease (the developer) and Aurecon (the engineers and anchor tenant) wanted a building that would visibly express sustainability and engineering, while providing a creative, collaborative workplace that would enhance the health and wellbeing of occupants. The opportunity arose to explore a timber structure to create a unique commercial building within the Brisbane office market, as part of the Brisbane Showgrounds precinct renewal.
This project was built to demonstrate to industry that performance solutions for this scale of building can be achieved to deliver a highly sustainable development that is low carbon, low waste and highly energy efficient.
25 King’s design appeals to the market appetite for office buildings that rethink architectural expression, commercial performance, wellbeing and sustainability. The natural warmth and glow of the building’s timber is integral to creating this appeal.
The primary engineered timber structure is made up of CLT walls, roof, and floor plates in European spruce, supported by glulam columns and beams in European spruce, with the addition of supplementary glulam beams reinforced with European hardwood LVL.
There are no timber infill wall panels in the building, as the floors at 25 King are open plan and wrapped with a full height glass facade.
Early documentation is necessary to enable prefabrication, requiring a very different approach to resolving the design, coordinating procurement and services, and finalising details ahead of construction, as it is difficult to make onsite adjustments. During construction, all timber elements were fabricated off site to minimise waste and facilitate transportation. Once on site, the prefabrication helped achieve significantly shorter construction times. With entire levels built in as little as eight days, and construction time totalling 15 months, this represented a reduction of 20 per cent compared to comparable steel and concrete buildings.
In terms of the material limitation, structural slab spans of 6m result in an increased number of columns however this configuration provides the best efficiency in terms of quantities of timber required. Double spanning 6m CLT panels, 12m in length, fit nicely in shipping containers and on trucks, making transportation efficient. The glulam beams span 8m between columns. The depth of the beam allows for structural penetrations that are sized to the distribution of services. Two shorter spans—one adjacent to the core and the other on the perimeter windows—create shallower structural depths to allow for the lateral distribution of large service ducts.
This combination of efficiencies allowed the creation of a tall timber building with flexible floorplates that maintain typical commercial floor to floor heights.
Architecturally, the building expresses the floorplates and use of timber through its glazed transparency. An angled street level timber colonnade provides a visual entry path to the structure.
Accoya timber has been used to clad to the exterior timber beams and integrated Accoya clads the external v-columns of the collonade.
A warmth and brigtness was created in the interior by leaving the wood and raw materials exposed. The interior palette is very simple and restrained, with the rational structural elements doing the hard lifting.