Summary
• Trussed rafters are increasingly being specified for architectural applications.
• The Code for Sustainable Homes means sustainable materials and energy performance are key.
• A pitched roof can house mechanical ventilation and renewable energy systems.
• BSW Timber Systems has supplied curved trusses to a retirement home in Worthing.

The market downturn has meant that the timber engineering industry has had to look further afield in order to keep production going. Timber has long been held up as a versatile architectural material but, with necessity the mother of invention, it is now being used more widely in architectural applications.

Traditionally associated with pitched roofs, truss rafters are pushing into new areas and are increasingly being specified for architectural applications. Here they are being manufactured in new ways to deliver more exciting architectural detailing than the traditional ‘up and over’ roof design.

The move away from flat-roofed buildings plays testament to the growth in popularity of pitched roofs. Instead, architectural design is seeing a resurgence thanks in part to the improved rainwater run-off characteristic, minimising the problem of water-ingress and leakages that a pitched roof delivers.

Flat to pitched roof conversions on existing buildings, both domestic and commercial, are also becoming more common thanks to the aesthetic appreciation for traditionally pitched slate tiled roofs coming to the fore. In more rural and suburban areas it may be more appropriate, and more acceptable to planning consent, for an office building or a new apartment building to have a pitched roof. Meanwhile many housing associations and RSLs are converting flat felt roofs to pitched roofs in order to improve the appearance and appeal of existing housing stock.

CSH drives the agenda

Legislation is playing an important part too. Despite the economic climate, the Code for Sustainable Homes (CSH) is driving the specification agenda for new homes. Particularly for housing associations and RSLs, which already need to be building to Code level 3, sustainable materials and the energy performance of buildings are key. There is more indication that developers are already looking to Code levels 4 and 5, introducing mechanical forms of ventilation and heat recovery as well as renewable energy such as solar photovoltaic systems.

A pitched roof incorporating timber truss rafters can contribute to the delivery of these elements. Primarily the timber used ensures that material sustainability is combined with the performance benefits required by the Code. A south-facing pitched roof makes the perfect foil for solar photovoltaic panels to operate effectively, while a pitched roof can be of a cold roof or warm roof design, depending on where the insulation is applied.

Trussed rafters and timber engineering are playing an important role in the sustainable development of architecturally-driven projects. Innovations in the manufacture of trussed rafters means that architectural designs that bring different elements to the standard pitched roof are being realised in timber. For example, where a roof was previously pitched at a 45° angle over a ridge, it can instead form a steadily sweeping curve.

Retirement development

BSW Timber Systems is completing a five-month long timber engineering project for McCarthy & Stone’s latest retirement development in Worthing. For McCarthy & Stone, architectural design that makes a positive contribution to the local surroundings is an important driver.

Consisting of three buildings, constructed in three phases, the specification was for masonry construction topped by a timber frame. Each building is consecutively higher than the previous and each one has a curved roof with a purlin detail.

“The effect is a series of three smooth curves rising one behind the other,” said Alan Beavis, BSW Timber Systems contracts manager.

Using Gang-Nail Systems’ Roof & Truss software, BSW Timber Systems’ Ramsgate factory manufactured the curved trusses, with attention to tolerances ensuring that the result was a precision-engineered product with a gradually curving profile. Once installed, an OSB layer is added to the trusses so that the roofing can be laid over the top.

Identifying market trends such as the popularity and growth areas for timber truss rafters, and the architectural detailing which can be achieved by innovating the standard manufacturing method to deliver bespoke curves, demonstrates how timber engineering companies can forge a path to new market opportunities.