This week’s structural special has all the latest innovations, from how to build a beer warehouse out of hemp to how to put up a concrete bungalow in two days. Plus, more news from the manufacturers

Product innovation: Things to do with hemp …

Down in the wilds of Suffolk work is about to start on what might be regarded as a dream project. It is a warehouse that will be built from hemp and used to store beer, and it is said it will probably be Britain’s greenest warehouse once it is completed next year. Lime products specialist Limetec is trialling a new construction method using hemp and lime blocks to construct the warehouse walls.

This is not the first time hemp has been used as a construction material. Architect Ralph Carpenter of Modece Architects has been championing the benefits of hemp for several years – his Suffolk village of Hartest is littered with hemp-built houses. These were built by mixing lime and hemp together and ramming the mix into shuttering rather like insitu concrete. It sets hard to form a structural wall with lime plaster used on the inside and a lime render externally.

The appeal of hemp construction lies in the fact that it is extremely green as it locks carbon dioxide up in the finished structure. This is because the hemp absorbs CO2 as it grows and the lime absorbs CO2 as it sets. Very little energy is needed to produce the materials and build the walls and, once constructed, hemp is a very good insulator that allows walls to “breathe”, keeping damp at bay.

The downside is that, until now, building with hemp has been very labour intensive, but Limetec is trying to make it as easy as building with conventional concrete blocks. The warehouse and distribution centre that Limetec hopes will showcase its construction method is being built in Southwold for brewer Adnams.

The 470 mm thick walls have a cavity wall constructed of two skins of blocks. This will then be filled with a lime–hemp mix that is blown into place by machine. The blocks need a high percentage of lime and a stone dust aggregate to give them the necessary structural strength, but this is not so good when it comes to thermal performance. The cavity infill therefore has a much higher proportion of hemp to provide better insulation. Limetec says the finished building will be so well insulated that no plant will be needed to prevent the cool beer from warming up.

In the next 12 to 18 months Limetec hopes to have developed the perfect lime and hemp block. This will have the structural properties of the blocks used on the Adnams building plus the insulation properties of the cavity infill. Limetec says the blocks currently meet British Standards requirements for strength so if it can crack this challenge there will be no reason why hemp construction shouldn’t hit the mainstream.

Limetec 301

Insulated concrete formwork

Logix Insulated Concrete Forms has introduced its insulated concrete formwork system to the UK. Called Logix, the company says it is a proven system, having been used in the USA for 10 years. The system comprises lightweight, expanded polystyrene interlocking blocks that act as both insulation and formwork for structural concrete. Each block consists of two panels separated by a series of struts to create a wall cavity for structural concrete. A house is built by fixing the blocks together, placing reinforcement in the cavity between the panels, then pouring the concrete. Plastic or metal sleeves are fixed into the wall prior to pouring the concrete to create voids for services and doors and windows. The company says installers can erect the blocks needed for a medium-sized bungalow in a day, then pour the concrete on day two. A range of blocks is available for creating corners of different angles, wall ends and “brick” ledges.

Logix Insulated Concrete Forms 302

Connectors for flooring

Steelwork connection specialist Access Technologies has added two connectors for fixing flooring to structural steelwork to its BeamClamp fixings range. The Floorfix clip is for connecting solid metal plate and the Grating Clip for connecting mesh to the structure.

The clips are suitable for fixing metal walkways and other flooring applications, and can be installed by one person from one side of the plate only.

Access Technologies 303

Beam and block flooring

Cement products maker Cemex has supplied its ReadyFloor precast beam and block flooring system to a Midas Homes social housing scheme at Gun Wharf in Plymouth. The beams were supplied cut to length ready for installing directly onto the footings. The blocks were then fitted between the beams and a concrete topping poured on. Construction then continued on the finished floor.

Cemex 304

Aircrete house system

Aircrete block maker H+H Celcon has launched a house construction concept said to make building a home much simpler. Called Rå House, it consists of the company’s aircrete blocks, intermediate flooring and roofing system plus an option for foundations. This structure is erected by H+H Celcon’s own installers using the company’s thin joint system. The housebuilder adds the external finish and completes the interior. The company says it offers build times similar to timber-frame construction without the lead time needed for manufacture, and that it is ideal for social and private housing.

H+H Celcon 305

Fibre-reinforced concrete

Richard Lees Steel Decking has teamed up with Grace Construction Products to launch a fibre-reinforced concrete for use with steel-deck composite floors. Richard Lees Steel Decking said the product eliminated the need for traditional mesh reinforcement. The synthetic fibres are called Strux 90/40 and are said to offer a higher strength-to-weight ratio than steel fibres. The fibres are supplied in 2.3 kg bags and are added to the concrete mix, which is then pumped conventionally into place.

Richard Lees Steel Decking/ Grace Construction Products 306

Pre-stressed concrete lintels

Naylor Lintels’ pre-stressed concrete lintels were specified for a retaining wall for a warehouse in Leeds. First, the steel columns were erected, then 400 pre-stressed concrete lintels were slotted between the steel columns. The client for the warehouse is the Ring Group and the contractor is Yorkstone Construction.

Naylor Lintels 307

Movers and makers

  • Conservatory roof specialist S&J Marketing has set up a portal frames operation. Called S&J Portal Frames, the company said recently there was enormous demand for engineered portal-frame conservatories. The company provides a complete design and installation service.

  • Whittles Publishing has launched a new edition of the book Basic Principles of Plates and Slabs – for safer and more cost effective structures. Written by Peter Lowe, it covers the theory, design and construction of structural floors. The book has been expanded and also covers new structural flooring technology.

  • BRE has published the 2005 edition of Concrete in Aggressive Ground. It is intended to help with the specification of below-ground concrete in ground where there are naturally occurring sulphates. It covers the assessment of chemically aggressive ground, recommends the specification of insitu concrete or precast concrete and blocks and pipeline systems. The publication has been extensively revised – amendments include changes to how ground is assessed and changes to concrete specification.

  • The Kingspan Group has formed a new division called Kingspan Century, which incorporates Kingspan Century Homes and Kingspan TEK. Kingspan Century Homes, which was formerly called Century Homes, is claimed to be the largest timber-frame building manufacturer in the UK and Ireland. Kingspan TEK makes structurally insulated panels for the UK, Ireland and Germany.

  • James Jones & Sons Timber Systems Division is the first company to receive environmental profiling registration from BRE Certification for its I-joist. The product is called JJI-Joist and the environmental impact of its production was subject to a 12-month cradle-to-grave assessment. The certification means housebuilders gain the BRE’s Ecopoints for using the product. It also meets the criteria for Green Guide to Housing A rating.

  • The American Hardwood Export Council has brought out a publication called Structural Design in American Hardwoods. It includes tests on four types of hardwood: white and red oak, tulipwood and ash. The tests were carried out by BRE for their strength classes and properties. The guide also contains information on European codes and standards and national design codes.

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