Fri 10 Oct 2008
Well structured
There are many factors to consider when choosing the fabric of a building. Roger Hunt explains.Two things are very clear when it comes to considering structural systems: there is no one-fits-all solution and thoughts about which products and materials are leading the way are constantly shifting. An uncertain economic climate brings even less clarity as the subtle balance between speed and cost changes.
When the sector is buoyant housebuilders are keen to use new materials and systems to help them build smarter and faster but in bad times this is not necessarily so true. In a climate of recovery, solutions that are readily available and can respond to short lead times will undoubtedly prove their worth and, where layoffs mean that the skill base of the onsite workforce has been lost, offsite and easily fabricated systems are likely to be in demand.
Masonry
According to Mike Leonard, director of the Modern Masonry Alliance, masonry is probably the cheapest construction method at the current time and has the major market share.
"Masonry provides high insulation and good thermal mass," says Leonard. "The key benefits of masonry in the current economic environment include the fact that no forward schedule is required as masonry is available off the shelf and it is fast and flexible. Added to these factors cost is driving private and public house builders back to masonry."
Traditionally offsite manufacture has been a challenge to brick makers but, increasingly, companies like Hanson are being seen as solution providers. Hanson has developed QuickBuild, a brick and block cavity wall prefabricated offsite that is craned into place. Used in the construction of the Hanson EcoHouse at the BRE Innovation Park, the walls comprise a 100mm stack-bonded Hanson clay facing brickwork outer leaf, 100mm Thermalite aircrete blockwork inner leaf and a partial fill cavity with 100mm rigid insulation and a 50mm air space.
"Whatever material you choose to construct houses from in the future it is about workmanship, feel and fit - that is the key," says Gerry Feenan, commercial director for Hanson building systems.
He points to the fact that offsite construction is influencing the quality of build that can be achieved. "It is lifting the way that new build is constructed in a traditional way and that will be added to by the benefits of offsite fabrication."
Another product to be showcased at the Innovation Park is H+H's storey-height aircrete panels which were used in the construction of the Barratt Green House. Measuring 600mm wide and 200mm thick, the panels are widely used in Scandinavia but are not currently marketed in the UK.
H+H UK is launching its next generation of thin-jointed aircrete products at Interbuild. Developed to improve site productivity, the new range consists of large format aircrete units manufactured in sizes designed to fit standard wall dimensions and offered as a complete wall system.
Wienerberger is gearing up to introduce Porotherm, a clay block walling system which is suitable for single skin walls with a render finish or, with a double skin option, with facing brick outer leaf. It may be built on site or can be supplied as pre-engineered wall panels.
The secret of Porotherm's thermal insulation lies in its 'open pore' design, explains Phil Noble, construction systems director at Wienerberger UK. "At the manufacturing stage, the clay is prepared and wood waste is added. The clay is then shaped, dried and fired at approximately 950¡C and, when the wood waste burns away without residue, it leaves countless tiny holes."
Clay is also the main ingredient of the "environmentally friendly and sustainable" lightweight concrete used by Kastell Building Systems in its pre-cast readily wired and insulated solid structures which are suitable for single dwellings and multi-storey residential applications. The walls are energy efficient due to thermal mass, solid and 365 mm thick or up to 400mm thick with U values down to 0.15 W/(m_K).
Lime Technology's new range of Hemcrete blocks combines carbon neutral properties with conventional block performance. Hemp is a natural material that locks in carbon as it grows and the blocks, available in structural or non structural form, are factory produced and the same size as conventional building blocks. Hemcrete - a bio-composite material that blends hemp with a special lime based binder to create a zero, or less than zero, carbon rating - has been available for several years as a cast or spray applied on site application.
Timber "As an industry we've been examining how we can drive costs out of the process," says Stewart Dalgarno, product development director for Stewart Milne Group and chairman of the UK Timber Frame Association (UKTFA).
"The sector is looking at factory fitting windows in timber frames and more integrated solutions such as pre-insulated panels that have airtight membranes fitted with service cavities already installed."
Kingspan Off-Site claims to be the largest provider of off-site construction systems in the UK and is consolidating this position by investing £2 million in CNC (computer numerical control) processing capability to allow production capacity of the Kingspan TEK building system to be increased.
This system achieves high levels of air-tightness by using a sealed jointing system to minimise the amount of air that can pass through the joints once constructed. The SIP-based timber framing systems are precision engineered and pre-insulated off-site.
According to Kingspan, an emerging trend in the housing industry is to combine off-site steel and timber through-wall systems with traditional methods such as concrete. This hybrid system is ideal where apartments are constructed above valuable retail space.
UK sawmillers James Jones & Sons has teamed up with Austrian timber processors the Binder Holz Group to create Binder-Jones, a specialist company which is supplying BBS cross laminated, solid wood structural panels.
Used extensively across Europe, BBS panels can be utilised for the entire building construction in a flat pack or finished pod; or for individual wall, floor and roof elements. They are specified because of their ease of construction, their ability to act as a structural diaphragm and a breathable building membrane. Additionally they offer enhanced thermal and acoustic properties due to the solid mass.
Born from the desire of architects to create an adaptable system for constructing buildings, FACIT is a company that has combined craftsmanship with digital technology to create a hybrid system which, according to Nick Willson, FACIT's architectural director, "takes a quantum leap in terms of adopting current technology to construct better designed and more efficient housing".
CNC and computer modelling technology allows for detailed customization down to the individual parts. FACIT's key components are cassettes made from flat sheets of 18mm spruce which are designed so that they interlock with a perimeter plate and each other to ensure accuracy in the setting out. Once erected on site they are filled with Warmcel insulation.
Steel "Steel has long been dominant in commercial buildings but, although the market for steel homes has grown rapidly, its percentage market share remains low in the residential sector," says Robert Clark, general manager, Fusion Building Systems UK. "This is strange considering steel offers a lightweight, structurally efficient, clean and environmentally friendly construction solution. Steel is one hundred per cent recyclable, is not prone to rot, infestation or moisture absorption and is dimensionally stable which greatly reduces the need for movement joints."
Fusion provides a complete system for the design, manufacture and erection of pre-insulated light gauge steel (LGS) frame buildings. It claims that its standard LGS walls are up to 60 per cent lighter than traditional construction walls while offering a very high strength to weight ratio, meaning less actual tonnage of steel is required.
Kingspan Off-Site is another manufacturer of off-site steel building systems and Trevor Harper, the company's project manager, explains that steel frame systems are become increasingly popular with developers constructing multi-storey apartment blocks. "Steel through-wall building systems provide the structural integrity and thermal efficiency required by such buildings."
A new building system from Corus not only facilitates efficient construction but also offers flexibility both in terms of design and use. Developed principally for use in the construction of two and seven storey residential developments, it is a hybrid of frame and infill panels and enables construction in stick form, panels or 3D volumetric units and works on the principle of a frame and infill system.
Modular building is ideally suited to situations where rapid build time and minimal disruption on site are essential. This is an area where Caledonian Building Systems specialises, designing, manufacturing and constructing multi-storey buildings using modules created from fully welded steel frames. These are fitted out in the factory as complete rooms, including plumbing and wiring, en suites and decoration, prior to delivery and installation on site. Services between the modules are connected with integrated vertical risers and central corridors used as distribution routes for the M&E.
Posted by Roger Hunt
in FACIT, Features, Fusion Building Systems, Gerry Feenan, H+H, Hanson, Mike Leonard, Modern Masonry Alliance, Nick Willson, Phil Noble, Robert Clark, Stewart Dalgarno, Stewart Milne Homes, Wienerberger on Fri 10 Oct 2008
Have your say and comment on this article