Unconventional Materiality: Timber, A European Perspective

“Unconventional materiality, I think, is an interesting way to think about timber from a real-world construction perspective. Civilizations have been using timber to build for thousands of years. However, as buildings have grown in ambition, scale and size, timber has fallen behind the more traditional construction materials of structural steelwork, and concrete. With carbon reduction targets, and pressures from clients and end users, we believe that view is about to change.

HARDMAN SQUARE

The Ivy sits at the centre of a cluster of highly impressive buildings within the Spinningfields development, standing against a backdrop of steel and glass structures. Part of the Allied London development, they said ‘The Pavilion will be greened and softened with landscaped ledges, adding some ever-needed public green space to the urban layout of Manchester City Centre’. There was only one way to realistically specify and design a structure with that brief, and that was by making use of mass timber.

Sheppard Robson, the project architect, also said they ‘were after a building that was different from the rest of Spinningfields and acted as a natural counterpoint to the glass and metal used on the adjacent blocks’. With both comments by Allied London and Sheppard Robson, you can really start to appreciate the thought process behind the material selection, not only for the carbon benefits, but heavily leaning into the aesthetic properties of the material as well.

The four-storey structure was made up of an innovative larch and spruce glulam frame over a regular six-meter grid. The glulam material was exposed externally on all elevations to clearly demonstrate the concept of the timber building, with a series of visual connections developed across the floor plates to keep in with the architectural vision. The upper floors and roof of the structure keep with a clear span of six meters for the CLT panels, yet due to the innovative CLT and Glulam Rib Deck solution - a prefabricated element tying together panelised and stick and beam construction methods - the overall depth of the panel remained relatively slim. For the engineers, the floor was designed to act as diaphragms which transfer the lateral loads from the façade to the CLT cores and braced CLT areas. By keeping the CLT and Glulam flooring system exposed internally, they provide a warm, natural space while feeding into the benefits of biophilic design, making The Ivy an incredibly pleasant place to be.

The on-site process with a mass timber structure is one of the major benefits of the material. By replacing time-consuming activities such as wet works, curing periods, and installing ceiling finishes, with simple screwed structural connections of mass timber – this provides a considerable saving to the front end of the on-site construction programme. On the Hardman Square project in particular, the use of the Glulam Rib Deck further improved construction time with the elements being prefabricated off-site for individual crane lifts. This also allowed following on trades to gain access to the building at an accelerated rate – generating a saving in main contractor preliminary costs.

Water management is one of the most important aspects of building with mass timber in the UK. Against common misconception, structural timber can go through wetting and drying processes during construction that does not affect the integrity of the timber. As part of our construction procedure on the Hardman Square project, we operated a strict moisture control plan which goes towards heavily reducing the risk of water staining and damage to the materials during the on-site processes. The moisture control plan has been developed over a number of years with our experience on mass timber and hybrid projects, and one is produced bespoke of every project that we install on site.

THE GRAMOPHONE WORKS

The Gramophone Works, in comparison to Hardman Square, is a commercial development sitting in West London. The campus has been developed to house a mixture of small and medium size creative enterprises situated in a mix of refurbished and extended office spaces. The space has been designed to promote creativity across the board and provide an inspirational workspace for the end users. While still following the same design principles as Hardman Square with a glulam frame and cross laminated timber decking to the upper floors, the structure makes excellent use of the existing concrete frame to form a true hybrid structure. With the current message in the construction industry being refurbish, re-new, re-use and recycle, this building is one of the best current examples of that message in action.

The structure, engineered by Heyne Tillet Steel, features a series of glulam columns, and beams to provide the overall frame, with a series of single and double height CLT walls to form the inner leaf of the structure. Tie this together with the exposed CLT floor panels, and you get an incredibly efficient mass timber building which acts as a carbon sink for sequestered carbon. This is one of my personal favourite areas of the project, the double height space on the ground floor of the structure. You can see the integration of the existing concrete frame with the cylindrical elements and the mass timber extension with double height CLT walls.

On the soffit of the space, you can just make out some of the glulam beams to tie the structure back together, making use of hidden connection details to really make the most out of the aesthetic features of the material. On the upper floors of the building, the theme of mass timber construction continues. Exposed visual soffits to the cross laminated timber create a seamless timber integration. The project makes use of two different visual grades of cross laminated timber across the structure – the floor panels are formed out of an industrial visual grade, and the walls out of a domestic visual grade.

By making use of areas of the existing structure, collaboration between all parties was an incredibly key part of the development. With the retained structure being exposed, major surveys were undertaken to ensure the sufficient setting out of the glulam and CLT elements. The columns sit on a larger 9-meter x 5-meter grid for the upper floors, allowing for a slightly more efficient, larger spanning panel when installing the cross laminated timber floor decks. The project also makes use of a CLT stair core to keep the lightweight mass timber benefits through-out the entirety of the structure, making for an efficient solution while maximising the use of mass-timber.

Hardman Square and The Gramophone Works are just two of B&K Structures’ recent projects which exemplify the potential of mass timber structures being built in the real world today. Only by working collaboratively as an industry – and sharing knowledge where we can – can we hope to reinstate timber as a ‘conventional’ materiality and combat the climate crisis.”

If you would like to find out more about these projects or please to a member or our team about engineered timber and hybrid structures, contact us or book a CPD today: https://www.bkstructures.co.uk/contact-us