Kevin Underwood of the British Woodworking Federation discusses the challenges as well as wide-ranging benefits of using wood as a construction material
Wood, the world’s oldest and most traditional building material, is increasingly being re-evaluated as a modern-day first choice for both structural and interior applications across domestic and commercial buildings. For example, the structural frame of the building, the roof trusses, flooring, walls, stairs, windows, doors and interior furnishings could in theory all be made from wood. As a renewable material coupled with modern manufacturing, wood is proving to be the catalyst for architecture and construction professionals in creating spaces that promote lower carbon emissions, longevity, beauty, and a real connection to nature. The ability to create both structural and aesthetic features from wood is due to the wide range of natural species and fabricated products available today. From natural hardwoods and softwoods, plywood and chipboard, to glued laminated (glulam) beams and cross-laminated timber (CLT), wood offers unique properties to architects which are all underpinned by the material’s inherent health and wellbeing benefits, added to its sustainable and physical characteristics.
Benefits of timber
The global movement towards creating spaces that are functional, practical and support the health and wellbeing of the building’s occupants, has driven up the use of wood as a building material. There is a growing desire among the occupants of commercial buildings to work in an environment with a high use of natural materials, with research finding that employee wellbeing was 15 per cent higher in office spaces where natural elements were incorporated. Natural building materials have also been found to improve both the mental and physical wellbeing of people by helping reduce stress, blood pressure and heart rates. From a functional perspective, wood also acts as a natural humidity regulator, which can absorb moisture from the atmosphere during times of higher humidity, and release moisture back into the atmosphere during dry periods. In addition, for commercial environments durability is essential, and this is where the specification of timber has proven benefits.
Take timber windows as an example, the 2013 report ‘Whole Life Analysis of Timber, Modified Timber and Aluminium-clad Timber Windows’ by Heriot-Watt University looked at a timber casement window made to Wood Window Alliance standards and found that the window had an expected average service life of 56 to 65 years depending on the level of exposure; double that of a PVCu window, which was found to have an average service life of between 26 to 35 years. This presents significant lifetime cost savings and longevity of build for both the current and future building owner. Wood is also the key component of in excess of four million timber fire doors manufactured across the UK each year, which help to save lives and protect property every day. Many Fire Door Alliance (FDA) members have taken part in the ongoing Ministry of Housing, Communities and Local Government (MHCLG) fire door investigation post-Grenfell, where the findings so far have shown that FDA member doors marketed to reach at least 30 minutes of performance have resisted fire for as long as 54 minutes, surpassing the 30 minute requirement by 24 minutes.
When specifying any material, there are considerations that need to be addressed and this can also be said for wood in commercial spaces. Many factors will be specific either to the building itself, the timeline of the project, or whether it is desired that a particular sustainability standard is achieved. For example, wood flooring is ideal for many commercial environments and can be used in conjunction with a concrete, steel or timber structural base. However, awareness and correct specification of uniquely engineered timbers is needed when accreditations, such as BREEAM, are desired. Ongoing innovation in manufacturing technology and engineered wood products has resulted in the material being used where previously it may not have been possible. A prime example is the Woodland Trust Headquarters in Grantham, where the building achieves a BREEAM ‘excellent’ rating by passively absorbing the excess heat generated by the office during the day. At the site, precast concrete “radiators” were bolted to the ceiling soffits of the CLT floor panels to enhance the thermal mass of the building while retaining the use of wood as the main construction material.
When considering specifying windows and doors, alongside the regulatory requirements associated with their use, such as anti-ligature guards, measures to prevent finger trapping or to protect people from falling, other characteristics of wood windows and doors need to be considered. This includes the product’s mechanical strength and security, weather resistance, thermal and acoustic insulation, heat and light transmission, operating forces, and long-term durability. Further to this an important consideration of any product specification is its ongoing maintenance requirements. All windows and doors require maintenance regardless of the material from which they are made. For example, the surfaces of the glazing and frame need regular cleaning and hardware requires lubrication. Within their service life many will also require re-glazing and seals may need to be replaced, so it’s important that all windows and doors are periodically checked for any damage or wear. For wood windows and doors, should any minor defects in the coating be detected during the inspection, these can be simply retouched with a spot repair.
This means that only a renovation coating needs to be applied to maintain the coating’s sheen, colour and durability, which effectively prevents the need for full redecoration. A clear demonstration of the longevity of timber products is the results from a recent trial at the Building Research Establishment (BRE), which involved BWF member Stora Enso Timber UK. The findings show that wood windows made from untreated heartwood redwood (pinus sylvestris) with a water based acrylic coating have remained in excellent condition after 14 years of south facing exposure with no intermediate maintenance, and will need only a simple refurbishment coat to extend their serviceability further. The opportunities for wood in commercial environments are vast, and with technological advancements creating innovative new wood products we only expect these to increase. For architects seeking support, guidance and expert technical insight, the British Woodworking Federation provides dedicated design guides and a technical advice line.
Kevin Underwood is technical director of the British Woodworking Federation