Barrett Byrd Associates

Conventional cavity wall house construction is set to be challenged by a single leaf masonry system known as Traditional Plus, reports Mike Walter.

Property developers in southern England face a huge task of meeting Government targets for 200,000 new homes to be built within 20 years. A shortage of skilled tradesmen including bricklayers is likely to mean slow progress with conventional house construction on such a large scale.

Enter the materials research specialist Ceram and its new system of wall construction known as ‘Traditional Plus’. The system comprises a single skin of masonry as opposed to two courses of brickwork used in cavity wall construction. Thermal and acoustic insulation are provided with a layer of expanded polystyrene and the wall is completed with an internal plasterboard finish.

Traditional Plus is the brainchild of Ceram’s head of building technology, Professor Geoff Edgell. “This system is not a huge leap of faith from what builders are already doing. It still involves the skills of bricklayers, but only one leaf has to be built instead of two,” he says.

An exterior wall constructed with Traditional Plus uses extra wide, 140mm bricks manufactured by Ibstock Brick of Walsall. Each brick has a higher degree of perforation than a standard UK brick, which makes their manufacture more energy efficient and the process of drying and firing easier. Each brick features a grip hole in the centre, which makes for simple handling on site and allows for special stainless steel joist hangers to be placed, from which internal floors can be constructed.

A suitable means of supporting a single leaf of masonry had to be identified and Edgell approached the foundation specialist Roger Bullivant Limited (RBL). At 140mm thick, the brickwork is less than half of the total width of a conventional cavity wall and RBL set about modifying its piling and ground beam system to suit the thickness of the slender wall.

Roger Bullivant created a reinforced concrete beam that was 300mm wide and 375mm tall to sit on a series of precast concrete piles driven into the ground. RBL also provided land for a two storey test house to be constructed at its headquarters near Burton-upon-Trent.

Edgell took the idea of single leaf masonry construction to Westbury Homes. The housebuilder agreed to take on the development of the Traditional Plus house at Burton and provided a bricklaying team. Once the superstructure was complete, the housebuilder fitted panels of 100mm thick Styrofoam insulation that was pre-bonded to 12.7mm plasterboard. The closed cell insulation, which is unaffected by contact with water, was secured to the brickwork using dabs of waterproof adhesive. “The use of adhesive in this way creates a nominal cavity from which to drain any water should it penetrate the brickwork,” says Edgell.

Traditional Plus is suitable for both detached and semi-detached buildings. When used for the latter, freestanding partitions can be installed either side of party walls to ensure noise does not travel between properties.

Details for the prototype house on the RBL’s site were extensively tested for thermal, acoustic and waterproofing performance as well as their resistance to wind. The house is currently in the process of gaining building control approval from South Derbyshire District Council and building type approval from Stoke City Council. “The test house at Burton has proved to be a very useful exercise and if it can secure building type approval I would hope that the system would be recognised by other authorities around the country.

“Builders tend to have their preferred ways of building houses but I would hope that Traditional Plus could be used extensively within a couple of years,” says Edgell.

A major opportunity for future use of the system has presented itself in Stoke on-Trent, one of nine areas in the country which the Government has identified as in need of funding to improve its stock of social housing.

“There are plans to knock down 14,000 tired old houses in the city and replace them with 12,000 new houses. This is a huge programme of construction and I would hope that the housing renewal team will devote a small estate to the use of Traditional Plus,” says Edgell. He adds that he would use such a project to further refine the construction process of the system.

Edgell hopes the single leaf wall system will inspire architects to develop other innovative housing systems that could be used in conjunction with Traditional Plus. To this end, he has submitted a bid to the regional development agency Advantage West Midlands to be involved in its competition ‘Famous By Design’ which invites students of architecture to work on leading-edge house design.

Edgell thinks that new ideas could include use of alternative heating systems, better disabled access into properties and alternative drain runs to make it easier to move bathroom furniture around. He adds: “There is plenty of scope for more innovation on the back of Traditional Plus and I would love to showcase new ideas in another of our show houses.“

BOX

Traditional Plus was formerly launched to housebuilders and property developers at the ‘100% Design’ building innovation exhibition at London’s Earl’s Court in September. The system may be new, but the concept of single skin house construction has evolved over the last two decades.

“Development of our single skin masonry system began in the early 1980s,” explains Professor Geoff Edgell of materials research specialist Ceram. “The clay brick industry was concerned about the rise in popularity of timber frame housing and decided that it wanted a system of house construction that relied structurally on a single leaf of brickwork.”

Early prototypes of single leaf masonry houses used 102mm thick bricks. A pair of semi detached houses, a dormer bungalow and an extension to a building were built in Stoke-on-Trent and 15 properties were built in Southend-on-Sea. The system gained building control approval and the early prototypes are occupied to this day, but question marks remained over the practicalities of construction.

“A single leaf of 102mm bricks proved to be fairly flimsy during construction and required exterior walls to be propped. The project at Southend was unfortunately not a commercial success and impetus ran out the idea,” says Edgell.

Further research and development by Edgell and his team led to the use of a brick 140mm thick, which removed the need for walls to be propped during construction. Other changes from the early designs included use of thicker insulation to meet improved thermal insulation requirements of the building regulations.

Ceram has produced a Traditional Plus design guide for single and two storey buildings. For more information, contact Professor Geoff Edgell on 01782 746476.

Back