Specification focus: Timber - 23 May 2007

The Blue Sky's the limit with wood

Blue Sky Residential found huge advantages in using timber frame compared with brick and block. James Stagg reports.

Blue Sky Residential's four-storey timber frame development in Buckley, Flintshire is being built with the ElecoFrame system.

In a departure from its usual method of construction, Blue Sky Residential is nearing completion on a four-storey timber frame development in Buckley, Flintshire. Having employed brick and block for all of its previous developments, the 60 one- and two-bed apartment project is the first time that Blue Sky has made use of timber frame construction.

Some £700,000-worth of timber frames have been supplied by Eleco Timber Frame. The factory-built structure has been used for the entire development and will be hidden behind an exterior of brick once the project is complete.

Blue Sky had taken the decision to experiment with timber frame in order to see if it could benefit from the system's perceived cost efficiencies and environmental credentials. "We had never used timber frame before," explains Haydn Gregson, director at Blue Sky Residential. "We have always used brick and block for our developments but decided that timber was the way forward. We considered a number of suppliers, but in the end chose Eleco for the quality of the products and the support the company could offer."

The ElecoFrame system comprises structural timber that is fixed using connector plates from Gang-Nail Systems. It also uses Ecojoist, a made-to-measure floor joist and ElecoFloor, a composite panel acoustic floating floor system.

"Eleco's wood is all regulated, which means that their panels are perfectly square," says Gregson. "The system is so accurate that two separate apartment blocks met exactly where they should, within a 3mm tolerance."

Blue Sky designed the development alongside Eleco, which advised on the best way to maximise the efficiency of the building method. Eleco then built the components and delivered all parts to the site. The panels are supplied as open frames to ease assembly, and arrive shrink-wrapped and labelled by plot. "They're simply tipped upright, nailed together and it's done," says Gregson. "We are so impressed that as a company we will never use brick and block again. You really don't understand the benefits until you actually use timber frame."

Speed of assembly

Unlike other timber frame systems, Eleco's system does not use sheathing board on the outer face of wall panels. Instead nail plates and diagonal bracing provide racking resistance as well as rigidity. Furthermore, by using the metal web, top hung Ecojoists there is no need for a ring beam or joist hangers, shrinkage is minimised and site erection is speeded up.

"The system does cost more than brick and block but you make up for with the time saved during construction," says Gregson. "It only takes two men to build one block and they were able to build four apartments a day. Also, we were able to erect it in any weather, further saving time."

All of the boards were delivered shrink-wrapped to protect them from the weather and they are referenced for easy location and supplied with guidelines and drawings. Once the frame had been erected Kingspan's rigid insulation was fitted to increase the energy efficiency of the development.

In terms of energy efficiency, Elecoframe is fully compliant with Part L and can be used with any external cladding material. It has been successfully tested for air tightness and can achieve u-values between 0.29W/m2k and 0.15W/m2K.

The floating floor system, ElecoFloor, provides compliance with Part E. The tongue-and-groove chipboard and acoustic board construction provides resistance to both impact and airborne sound. By using ElecoFloor, it is possible to save on the outer brick course or exterior render required on multiple storey buildings and the related product and installation costs. Eleco estimates that using ElecoFloor in conjunction with Ecojoist overall build time savings of 30% can be achieved, when compared with traditional onsite construction methods.

"We found that there were massive advantages compared with brick and block. The structure went up incredibly quickly and the minute the osb floor was installed our plumbers and electricians were working below. We were also able to plan efficiently, with fewer trades coming on site we knew exactly when and where everyone should be," concludes Gregson.

Reasons to go with the grain

Nick Moore from Timber Trends, in association with Gardiner and Theobold, provides the wood facts.

Timber has been used for building since the earliest days of man and continues to be used as a prime building material in today's world.

In many countries timber is the main building material of choice, used structurally (beams, posts and for making roofs) functionally (doors, windows and floors) and decoratively (mouldings, claddings and decorative surfaces).

In structural building applications, timber frame construction is widely used because in many situations it is simply quicker to build with because it meets and often exceeds building regulations and standard requirements for thermal insulation, sound transference and air tightness and outperforms many of the so-called 'traditional' building materials.

Demand and supply-led price pressure

Recent trends in the global economy, such as rapidly rising energy costs and rising levels of raw material prices have been induced in part by a generally buoyant world economy.

Fuelled by strong growth in the US and the emerging (and surging) economies of China, India and other smaller nations, the demand for products and services of all types has been high.

The demand that the rapidly expanding Chinese economy is placing on commodities of many kinds has helped to fuel the rising costs of raw materials and there is a similar effect for the raw material from which timber is made: logs.

Price deflation has been the 'norm' for many years in the timber industry, where the 'real' inflation adjusted price of timber has resulted in lower revenues per m3. This has been true for virtually every producing country, including Sweden, one of Europe's most important producers and the largest supplier of sawn softwood to the UK market.

The general price level for its sawn redwood has been, at best, stable over a period of many years as Chart 1 (see right) describes. The prices shown are export prices in local currency, free-on-board.

Pricing and the near future

The year 2006 can be seen as one where the 'balance' between consumption and production started the process of correction towards a more benign supply and pricing environment. Nevertheless, it is doubtful that timber prices will reduce again to the levels where it became economically unjustifiable for some firms to continue trading.

The ramifications of this for the house-building and construction industries are clear: to continue to enjoy the rewards that timber products provide, higher prices will need to be factored into building projects, now and over the long-term.

Fortunately, the benefits provided by timber products continue to outweigh any price burden, especially when compared with the recent rises in energy costs and other raw materials.

WRAP recycled wood products

Contractors and specifiers are commonly using wood products with a high level of recycled content, as highlighted by the panel-board industry using almost 85% of the recycled wood available in the UK.

Hardboard products are available with around 60% recycled wood, while particleboard or chipboard can be sourced with a recycled content of 90% or more.

Landscaping is one area where there is the potential for the construction industry to use more recycled wood. Many developers will use bark or woodchip to make communal flower beds and landscaping look more attractive while reducing maintenance. Made from used pallets - many of which will have been used to deliver construction products - recycled woodchip is a popular and long-lasting alternative to virgin materials.

Timber is one material that will make up a large proportion of the waste generated on site - especially in the form of off-cuts and used pallets. It is an incredibly easy material to recover and recycle, but contractors should look to segregate used wood on site by providing a dedicated area or skip.

Re-using off-cuts and sending segregated timber for recycling will help save costs on both disposal and new materials.

As well as using the recycled material to manufacture products for the construction industry, off-cuts and pallets are also finding their way into new areas - such as high-quality equine bedding.

Waste & Resources Action Programme (WRAP) is supporting the recycling of construction and demolition wood waste through the provision of capital grant funding, which will be used to accelerate higher value wood recycling and create new wood reprocessing infrastructures to divert wood waste from landfill.

Because of the slowing of production in 2005 and the continuation of strong demand, the balance of trade became negative where demand outstripped production. The shortage of sawn softwood in 2005 was estimated to be in the region of 2.5 million m3.

As a result, stockholdings reduced around the globe to 'take up the slack', but because such events invariably created an uneven supply pattern against demand, further pressure was exerted on price.

Contract Journal looks at the various wood solutions currently available.

Stay-Dry

Chandos Timber Engineering has completed the building structure of the North West's first six-storey timber apartment block. The development of 52 apartments in Manchester is being built by local housebuilder Haigh and Haigh. The builder chose timber rather than brick and block for its environmental and cost efficiencies, and is one of the first to make use of the 'stay-dry' timber developed by Chandos. The timber is treated in order to minimise shrinkage and movement to provide an accurate build.

Ecohomes

Integra has achieved a 'very good' rating under the EcoHomes initiative for its construction of 31 flats at Bevendean, Brighton. The £2.7m flagship development was part of an NEC partnering agreement between Integra and Downland Housing Association. The units form part of the association's housing stock available for rent and shared ownership. The buildings feature sweet chestnut cladding on a structural insulated panel superstructure with green roofs installed on both blocks.

Timber Frame

Modern methods of construction specialist Pace Timber Systems has partnered with Higgins Construction on a £1.2m mixed-tenure development for recently merged RSL client Circle Anglia. For the development's three-storey block of six flats and four two-storey houses Pace supplied a timber-frame solution comprising all internal and external walls, prefabricated cassette floor joist systems and roof structure. The company also supplied pre-finished bathroom pods. With a floor area of 4m2, each pod features a factory installed WC, bath, washbasin, tiles and heating radiator. Built to comply with Lifetime Homes' requirements, each pod has knockout panels incorporated into the design to cater for any future adaptations.

Timberkit

Robertson Timberkit has unveiled a new £200,000 production line at its Seaham plant, representing the growing demand for timberkit products. The company manufactures timber frame solutions and posted a turnover of £22m in 2006. Its chief executive, Ron Easton, said that the semi-automated line will improve the company's manufacturing operations and allow it to meet the demands of an expanding and increasingly competitive market. "The new line will also allow us to fully utilise the assets we have on site by increasing our shift capacity while giving us the added flexibility to efficiently service varying seasonal demands," he added.

Decors

James Latham now distributes Zoom, the latest concept from Egger. Zoom is a range of colour co-ordinated decors that comprises Eurodekor melamine-faced chipboard, Eurodekor melamine-faced MDF, Euroform laminate and Euroform melamine edging. The portfolio is aimed at the shopfitting sector and includes 78 classic and contemporary decors.

Green guide

Following an assessment of their environmental profile by BRE Certification, NBT's Pavaclad and Diffutherm timber frame building systems have each achieved an 'A' rating in the BRE's Green Guide to Housing Specification. The company's Pavatex insulation systems were assessed as part of its Pavaclad and Diffutherm timber fame building systems, finished in both render and timber cladding. The Pavatex insulation board scored -0.33 and the insulated sarking board scored -0.79.

Cladding

Responding to the increasing popularity of timber cladding, John Brash now offers a cladding range to join its range of roofing battens, scaffold boards, cedar shingles and shakes. The company says that the use of timber cladding can reduce building costs, due to the low weight and high insulation properties of the material. If used alongside similar lightweight roof coverings, such as shingles, the need for bulk masonry walls is eliminated, reducing the level of foundations required.

Wigan Pier

Part of the £200m regeneration on Wigan Pier, a six-storey timber-frame residential development has been constructed using iLevel Trus Joist engineered floors. Yorkshire-based Shire Timber Structures used 17,500m of the joists in varying sizes. To meet the disproportionate collapse requirements laid out in the Building Regulations, over 4,000m of Parallam PSL was also installed around the perimeter of each floor to support its load should a wall panel be removed.