Off site timber frame construction is now recognised as a good strategy for minimising waste through efficient manufacturing and design processes. Also known as Modern Methods of Construction (MMC), offsite construction has many distinct advantages. Benefits such as quality, shortened construction times, cost control, increases in quality and environmental credentials have led to MMC becoming adopted by the construction industry.
Off site timber construction can help to dramatically reduce the amount of on-site waste that is generated during the assembly and erection of a building.
The Role of Construction in Sustainable Development
The construction industry has a huge impact on everybody’s quality of life by contributing to sustainable development. The focus of sustainable development is on making improvements to the quality of life for everyone, while minimising the use of natural resources. This ensures that these natural resources are not consumed beyond the environments capacity to indefinitely supply these materials.
In fact, sustainable development is as old as humanity itself. Historically many cultures have identified the need to live harmoniously with nature, and to consume natural resources responsibly.
Off Site Timber Frames
In many parts of the world it is now understood that off site timber frames are a sustainable construction solution that lend themselves well to small buildings in all sectors. Timber frames are environmentally friendly in many ways. The timber itself is a product of sustainably managed forests. However, because the frames are assembled at the factory, there is no onsite waste. A significant amount of wasted timber can be generated through off cuts alone. Timber at the factory can be cut to ensure that waste is minimised. Any waste that is produced can then be used to produce lower grade timber products such as MDF and chip board. The amount of waste that is sent to landfill is negligible.
There is now legislation throughout EU member states that specifically requires contractors and developers to deal with waste efficiently. This is as cost effective as it is environmentally sound.
The thermo-efficient properties of wood make it a naturally ecologically sound building material. This is one of the reasons for its popularity in Scandinavian countries and other countries with colder climates such as Canada. The availability of the material has also historically made it an obvious choice.
However, increasing environmental credentials is not the only benefit. When timber frames are manufactured off site, they can be subjected to far more rigorous quality control procedures. Many manufacturers of timber frames within the EU use only the highest quality and certified materials. Typically only EU sustainably produced slow growing hardwoods are used. This minimises the environmental impact of the product, but it also ensures that the timber is both rigid and strong.
Timber frame construction also allows for floor cassettes and floor panels to be produced within a controlled environment. This means that the product can be tested on multiple occasions before it reaches the site. Because each element of the superstructure is checked so thoroughly to ensure accuracy, this enables rapid assembly and erection.
Timber frame construction has been an industry standard in Scandinavia and other Northern European countries. However, until recently, brick and block construction has been the traditional choice for residential dwellings in the UK.
Timber frame construction has become more common in the UK in recent years. It is now mainly used for residential single occupancy dwellings of 3 stories or less, small commercial buildings of under seven stories and small institutional buildings of under seven stories.
The United Kingdom’s timber frame market generally consists of three forms of assembly:
1, Stick build: This is where timber is pre-cut to length for joists, studs but assorted random lengths are also included for top plates, bottom plates and the sole. These are delivered to site as kits which are then assembled.
2, Panelised walls: This makes up a majority of timber frame construction in the UK. Pre-manufactured timber frame panels are delivered to site. Upon arrival they are ready for assembly to form both non-load bearing interior partition walls and structural load bearing walls. Panelised wall elements usually include features such as windows, doors, insulation, services, interior lining and exterior finishes.
3, Roof/floor cassettes: These are similar to the wall panels, only they are manufactured to a larger size that is suitable for floors and roofs. Floor boards, beams and the joists are included at the very least. Services, lining and insulation can also be added during the manufacturing process in more advanced systems.
Generally speaking, a huge advantage of timber frame structures is that no further modification of the elements is required during assembly and erection. However, when completing some interior patrician walls and external load bearing walls, it will be necessary to use various loose materials which often include:
- Nails and screws
- Plastic and timber shims
- Connecting plates and sole plates
- Breather membrane
- A vapour control layer (often polyethylene)
- Insulation (this is most likely to be mineral fibre)
The engineer is able to have an in depth and precise understanding and knowledge of materials that are required for the assembly of a structure. This is applicable both on site and at the factory. The elements are billable and therefore traceable and this, in turn, means that controlling any additional materials which may be sent to site is easier. This is highly advantageous in terms of eliminating the unnecessary waste of materials. The main operations on site are limited to the unloading of materials and assembly of floor, roof and wall panels to complete the structure. This is usually accomplished by nailing panels together and further modifications are not required. Most of the waste was generated during the manufacturing process at the factory.
The timber frame industry is typically responsible and pro-active when it comes to working with low carbon, sustainable and natural materials. However, the timber frame industry is able to offer significant benefits to the wider construction industry. Timber frames have a significant positive impact on the construction of buildings in terms of reducing the carbon footprint of structures and sustainability.
Many companies that manufacture timber frames constantly review their design and manufacturing processes. They also understand the need to invest in machinery and software which will optimise efficiency and reduce waste even further. Many even recycle their waste to produce other lower grade timber products at the factory.
This approach dramatically reduces the demand for raw materials as well as the amount of waste produced. Waste is segregated at the point of generation and the management of this waste can be combined with reusing and recycling materials. The production of zero waste to landfill is achievable.
Nordic countries have a long tradition of using wood as a construction material and Finland is no exception. Log cabins, churches, town halls and other buildings such as traditional Finnish bbq huts were constructed from logs, and sometimes entire tree trunks, due to the abundance of timber growing freely in this region.
Traditional Finnish log construction is characterised by a distinctive simplicity. The uncomplicated rectangular buildings with gently sloping roofs are much the same as today’s modern log cabins and bbq huts. This style of building has been enjoying a revival in recent years. During the early part of the 20th Century, the American lightweight timber frame style of building, then new, was widely adopted in Finland, and mostly replaced the native style of log construction by the 1930’s.
Before long, lightweight timber frame structures became the favoured option, with traditional log construction being viewed as outdated. The opinion was, that the traditional Finnish log construction method too laborious, and timber frame structures used less used wood, and were quicker to erect.
Aside from a post war period of reconstruction in Finland, when nails and other resources were scarce, traditional log construction became an antiquated and obscure building method. Many of the original log structures were demolished during the 1960’s and 1970’s, and very few remain today. The general consensus was that new buildings were easier to construct, in comparison to repairing or renovating old log structures.
Recently, the positive qualities of log buildings have led to people embracing traditional Finnish construction methods and architecture once again. Log buildings are now considered to be durable, aesthetically pleasing and ecologically sustainable structures of an extremely high quality. Log buildings are also perceived as being ‘healthy buildings’, due to the fact that there is a good amount of air flow within them, which permits the buildings to ‘breathe’.
So, are these structures healthier? Although this question has not been widely researched, there does appear to be some evidence to back this up this claim. Recent studies by the Research Centre of Finland (VVT), did show that wood, when used as a hygroscopic material, could noticeably improve the air quality inside a building. Wood could also potentially reduce the need for heating. This is because the hygroscopic material (wood) allows for more air to circulate, which in turn, cuts down the need for ventilation by up to 15%, so less heat can escape.
The 1950’s saw the beginning of the industrialisation of log construction, leading to industrially produced round logs replacing the hand hewn variety. At this point, there was little input from experts such as architects and designers, but this changed in the 1960’s to 1970’s when the market for log buildings opened up. Technologies such as CAD, have allowed for traditional style log structures to be mass produced to a very high standard. Today, Finnish industrially produced log cabins and other types of buildings have become country’s chief export, with the products being shipped to over 30 countries worldwide.
Finland is now home to the world’s leading log factories and log construction companies. These traditional Finnish log buildings are not just exported, and domestic sales have increased, with log structures accounting for 10% of all new homes built. These new builds are mainly in rural areas, but more homeowners than ever are interested in this style of home. There are also moves to reintroduce the log building back into Finland’s towns and cities.
The University of Oulo has played an important role in the modern revival of traditional Finnish wood buildings. The Wood Studio of the Department of Architecture, has run many competitions for students to explore this traditional construction method with fresh eyes.
Other projects in Finland such as the Kierikki Centre, which is the country’s largest log building, and the Kärsämäki shingle clad wooden church, have become flagships for traditional Finnish log construction, but with a modern twist. These structures are elegant, simple and durable.
Managing forests in regards to conservation was addressed in 1992 at the United Nation’s Rio de Janeiro Earth Summit, also known as the Conference on Environment and Development. At that time, the need to develop an international model for sustainable forestry practices was identified. This was due to concern over the rapid deforestation in certain parts of the globe.
The UK was among one of the countries that highlighted the need for an international agreement that would be legally binding, in regards to a framework for sustainably managing the world’s forest resources. The goal was a Convention to compliment those on Climate Change, Desertification and Biological Diversity. However, there were other countries that objected to a Convention on Forests, as they believed that this would lead to their rights to use their own natural resources being compromised. Due to this opposition the Statement of Forest Principles, which is non-legally binding, was introduced instead of a Convention.
The Statement of Forest Principals established a global framework for the conservation, development and sustainable management of forests.
In global terms, The UK’s forests cover a small area. However, the United Kingdom’s Forestry Commission plays a significant role in international debates and discussions on forestry. They have been instrumental in their contribution to the development of international sustainable forestry policy. They are committed to sustainable forest management and even co-operate with developing countries on sustainable forestry issues.
Part of the Forestry Commissions’ commitment to sustainable forestry is an emphasis on conservation. Cooperation with charitable trusts such as the Wildlife Trusts, National Trust and Woodland Trust ensures that conservation in UK forests is well supported. This is integral to sustainable forest management as outlined in the UN Statement of Forest Principles.
The Royal Forest of Dean and the Forestry Commission’s Role in Supporting Conservation and Biological Diversity
The Forest of Dean is one of the surviving ancient woodlands in the United Kingdom. Situated in the county of Gloucestershire, England, the mixed woodland covers an area of approximately 100 square kilometres. Today it remains a sustainable working timber producing forest. Although the Forest of Dean consists of mixed deciduous and evergreen woodland, many non-native species of tree are grown for timber production. These include the Japanese Larch, Douglas Fir and Scots Pine. While the Scots Pine occurs naturally in Scotland, it is not native to the South of England.
A balance must be achieved between sustainably grown non-native timber plantations and conserving habitats for native species of plant, insects and animals. Areas that have been specifically allocated for sustainable timber production are offset by nature reserves and conservation areas in the Forest of Dean.
A Forestry Commission Recreation Ranger leads a voluntary group called the Forest of Dean Green Team. Activities such as clearing shrubs and other plants in to maintain habitats for species of plants and animals are undertaken. The county’s leading conservation charity, the Gloucestershire Wildlife Trust, owns and manages reserves within the Forest of Dean and works with the Forestry Commission to maintain biodiversity and to preserve vital habitats for native species.
Gloucestershire Wildlife Trust and the Living Landscapes Project
The Local Action Group awarded the Gloucestershire Wildlife Trust a sum of almost £68,000 In January 2011 for their ‘Living Landscapes’ project.
The objective of ‘Living Landscapes’ is the long term implementation of habitat restoration within the county of Gloucestershire. This vision of a sustainable future for wildlife encompasses the Forest of Dean. However, the Gloucestershire Wildlife Trust recognises that if the wildlife in the forest is to be sustained, it must be valued by residents. They are working to link residents, the economy and wildlife in order to establish a living landscape within in the Forest of Dean.
Their holistic approach places great emphasis on assisting Forest of Dean residents in connecting with the wildlife in their area. This enables people to identify the unique wildlife that defines their area. This involves working pro actively with the residents in the following ways:
• Identifying wildlife species that are unique to the area and creating Parish Wildlife Maps. The aim of this is to produce maps that will help residents to explore and gain a greater appreciation of their surroundings.
• Training residents in monitoring and surveying skills means that local people are undertaking a land-use survey which can be compared to the findings of a similar previous survey of 1974. This will help to show and quantify changes in land-use. The results will help to motivate residents to become more proactive in conserving local habitats. It will also be useful in influencing planning decisions.
• The Trust are training residents to survey for local species including key local species and Biodiversity Action Plan (BPA) species. This means that residents are able to actively participate in supporting their local wildlife.
• There is also the more practical side of managing habitats on the Trust’s Forest of Dean nature reserves. Tasks are carried by staff and volunteers. The flagship of this is the Woorgreens site where the Trust have partnered with the Forestry Commission. Residents have the opportunity to take an active role in practical conservation and learning new skills in this area.
• Events such as wildlife walks and talks will be a vital component of promoting the enjoyment of these unique local habitats.
Visitors to the Forest of Dean play an important part in the local economy, and this impacts upon residents. A part of encouraging residents to value local wildlife is identifying the fact that a main attraction of the Forest of Dean is the area’s unique wildlife. The Trust will run activities aimed specifically at visitors and will provide leaflets of walks that link nature reserves and other sites of interest. Guided walks are also an important part of this.
Beth Adams of the Gloucestershire Wildlife Trust Takes a Closer Look at Sustainable Woodland and Forest Management in Nature Reserves.
Beth Adams, Volunteer Coordinator at the Gloucestershire Wildlife Trust, understands the important role that residents have to play in conserving unique local habitats. She is also a resident of the Forest of Dean and has previous experience working as a ranger in Hatfield Forest for the National Trust.
The local Woorgreens nature reserve is a good example of how these elements interact in regards to sustainable forestry. Areas of working forest for timber production surround the Trust’s reserve. In fact, in 2012 the Forestry Commission has already cleared a large area of trees so that the area can be managed for heathland. This is an important natural forest habitat for reptiles, insects, birds and certain plant species such as heather. However, the reserve itself is managed sustainably, as Beth explains.
Sustainable forestry is a huge area, and if you ask some people, sustainable forestry is all about timber production, for some it will be all about conservation and for others it will mean social involvement.
The management of woodlands and forests covers broad economic, environmental and social goals. A significant part of my personal experience in sustainable woodland management is in coppicing. This is an ancient traditional management technique, dating back possibly as far as the Iron Age when people cleared the land.
Coppicing is the art of cutting back trees to within 10 to 20 mm of the stump. Clean stems are left from which suckers or shoots will grow. These coppice stools can then be harvested from anywhere between 7 to 20 years of age. Coppiced species at Woorgreens include trees such as Alder.
We coppice between October and March, because it is easier at this time. Volunteers are encouraged to participate of course! There is less surrounding vegetative growth. Coppicing should not be done after the end of February. This is because we want to ensure that as little damage as possible is done to existing flora. Also, as the bird breeding season is between March to July, we really want to avoid this too. Coppice should not be cut in August either, as this encourages late shoots which will not ripen before the first frosts.
Trees are maintained at a juvenile stage which means that they will never die of old age. Some of the coppice stools that exist today are hundreds and even thousands of years old.
We cut coppice in sections which are known as coups. They are cut on a rotation basis to ensure that there is a coup at every stage of growth. Each year a coup will be cut, so this is sustainable as each year a coup is ready.
Almost all of the native British trees are capable of sprouting new shoots from the cut stumps of established trees. The least vigorous in this respect are the Beech, Birch and Hornbeam.
Managed coppices have a particularly rich flora and fauna. The cyclical cutting of the underwood on a repeated basis opens up the canopy, which encourages a varied ground flora. It also provides both open and sheltered and open spaces. This is a good habitat for birds such as warblers and nightingales. It also creates a good habitat for butterflies, reptiles and dormice too.
Our reserves in the Forest of Dean are managed sustainably and coppicing plays a very important role in this. A further benefit of this is coppicing produce cut from coppice poles.
• Fencing stakes
• Hedging stakes
• Bean poles
• Pea sticks
• Tree sticks
• Fire wood
A Closer Look at Woorgreens Nature Reserve
Woorgreens Nature Reserve is a great example of how the demand for timber and conservation of habitats can be balanced by managing a forest sustainably. The Woorgreens reserve is owned by the Forestry Commission and jointly managed by The Gloucestershire Wildlife Trust. This results in valuable habitats and biological diversity being maintained.
However, thanks to the joint efforts of the Forestry Commission and Gloucestershire Wildlife Trust, residents have been encouraged to actively contribute to this conservation. This has engaged local people, and helped them gain a greater appreciation of their local wildlife. Volunteering has been instrumental in this. Large areas of the forest are still available for the creation of plantations for non-native species of tree to be used for sustainable timber production.
In fact, Woorgreens is something of a flagship. The reserve is managed sustainably as we have seen. Events and wildlife walks are held at Woorgreens, so the public are actively encouraged to engage with their environment. Thanks to the efforts of the Gloucestershire Wildlife Trust and Forestry Commission, this nature reserve encompasses many important habitats.
• Margins of scalloped grassland support species of caterpillars and butterflies such as the speckled wood, meadow brown and gatekeeper.
• Wet and dry heath ride encourages a dense mixture of bare ground, gorse and heather. This is an ideal habitat for lizards and the adder. Nightjars can be heard in the summer months. This rare bird migrates from Africa to nest in parts of the UK during the late spring and summer.
• Woorgreens Lake is home to species of bird such as mallards, greylag geese and the golden eye. Species of dragonfly and damsel fly such as the brown hawker, common migrant, emperor, ruby darter and large red damsel fly can also be observed at the lake.
• A network of smaller ponds in the reserve, which are linked by ditches create vital areas for frogs, toads and the great crested newt.
• Open grassy areas provide areas in which reptiles such as slow worms and grass snakes can bask in the sun. These areas are also important for species of moth and butterfly.
• The edges of the reserve, where the open areas meet the surrounding forest are of equal importance. These areas are an important habitat for small mammals such as shrews and voles. Many plants also thrive in these sunnier conditions and encourage a greater variety of insects and birds.
Sustainable Forestry Actively Supports Biological Diversity and Impacts Positively Upon Local Communities
It is important to consider the expectations of consumers in regards to sustainable timber products. Because people have become more aware of their impact on the natural environment, conscience is a significant concern when it comes to choosing products. People now expect timber products to originate from sources where such initiatives are a matter of course.
However, such practices are now commonplace within many countries that produce timber, thus balancing economic concerns such as timber production with the issue of conservation. This holistic approach is the essence of sustainable forest management. Many groups and organisations can take an active role and cooperate with one another to ensure sustainability in many diverse ways. Natural resources are managed with maximum efficiency, while biodiversity and the conservation of natural and native habitats is not just maintained, but actively encouraged.