Since energy and natural resources are consumed, and waste created, in both the creation and destruction of buildings, lifespan is an important marker of sustainability.
Brick's long-term durability is rarely in question, ensured not only by its technical longevity but also by its flexibility, which makes re-use simpler. This is apparent when one considers the number of refurbished Victorian buildings that have found a new lease of life with a change of use, for example, the dockland warehouses that are now being used as accommodation and offices.
In some cases, old buildings are simply repointed to provide several decades of extended life. In others, bricks may be completely reclaimed - dismantled, 'dressed' and re-used to alter and extend existing structures. Other ways to extend the life of buildings may involve manufacturing new products, which match existing products.
These new products are designed to look like old bricks, being tumbled, chipped and splashed with paint to give the desired weathered appearance, but would, of course, carry a 60-year warranty.
Structural use of loadbearing masonry has been promoted for many years - long before 'sustainable construction' became fashionable. Historically, brickwork was used for its high load-carrying capacity as well as its durability and aesthetic appeal.
But the introduction of the energy-efficient cavity wall put paid to brick's structural characteristics.
However, a revived promotion of structural brickwork then took place from the late 1960s. The promotional angle was that if structural masonry was used, it was possible to reduce overall building costs because you would not need structural frames of steel or concrete.
This scenario is fine for certain building types, such as diaphragm and fin walls for large open-plan structures. Retaining walls provided clay brickwork as both the highquality finish and the structural element.
Now we can revive the structural brickwork story, but this time from the point of view of sustainability rather than of straightforward economy.
As U-values continue to become more stringent, cavities are becoming wider and techniques of cavity wall construction are changing with, for example, the use of partial fill. These changes create additional costs with longer wall ties, increased insulation, and increased overall wall thickness which means either sacrificing habitable floor space or increasing the land area for each dwelling.
Although bricks and brickwork as a material cannot influence the overall thermal efficiency of a wall significantly, cost savings can be made by tackling the problem of thicker walls. This can be done by reducing the thickness of the outer leaf.
Whereas standard UK bricks are 102.5mm thick, a number of products are made 90mm thick as standard. This may not look like much of a saving but it represents a decrease of 10 per cent in the width of the outer leaf.
In addition to the reduction in the building footprint, there is the volume of clay saved per m 2, which represents a saving in raw material and in the energy costs for firing. In addition, less mortar is used in the 90mm thick wall. This may be a simplistic analysis of sustainable design, but the issues are worthy of consideration.
While clay brick is not the most thermally efficient building material, this does not mean that it has no contribution to make to the environmental performance of the building.
Clay brick has good sound-insulation characteristics and provides thermal mass, ie stores heat. This may be experienced when walking past a brickwork wall at the end of a cold but sunny day, and feeling radiant heat.
The process of supplying architects with samples of bricks has traditionally been high in energy and consumption of materials.
Countless bricks are used for samples each year. These have to be presented in box-type packaging. Postage or transport is also expensive, with knock-on environmental implications.
Countless more bricks are cut into slips, and MDF and glue are used in forming sample panels. Again there are the costs and issues of transportation.
To tackle these issues, Hanson Brick has now increased the number of very highquality, high-resolution photographic panels that it uses instead of sample panels.
The cost of printing is far less than the cost of making up panels, and the transport cost is negligible.
Electronically generated panel libraries and rendered-image details of architects' designs give a much better idea of what the finished building will look like. It is easier to change brick-and-mortar options by using computer-generated images. By tackling the issues of cost and sustainability, the service to the client is also improved.
Many a slip
Many new and innovative facade systems, which are required to have a clay brickwork finish, benefit from the use of brick slips rather than full-size traditional bricks. Slips possess all the aesthetic qualities of bricks and will demonstrate durability characteristics in keeping with the brick from which they are formed.
The use of brick slips could seem like a logical continuation of the material savings offered by using more slender bricks. In fact, the most common method of producing slips is by cutting them from full-size clay units. While there is an obvious concern as to the sustainability issue - slips cut from extruded bricks leave some 75 per cent of the clay body useful for nothing more than recycled aggregate - the current demand is still a very small percentage of the brick market.
The seemingly obvious alternative is fraught with difficulty. Where slips have been pressed or extruded successfully, they suffer from a bland 'perfect' appearance that distinguishes them easily from the diverse characteristics of many clay bricks.
But where slips are produced by cutting from clay units with two faces, the waste factor is minimal as almost all of the brick is used.
General benefits of slips in terms of sustainability include:
Lower volumes of clay used to give a brickwork appearance;
Greater number of slips transported for a given lorry load (four times the number of bricks);
Prefabricated panels benefit from the lighter weight of slips;
Reduced loads transferred to the superstructure.
Construction techniques Bricklaying costs per square metre will depend upon the number of units laid per day.Quite often, if we introduce a product of non-standard format (that is, not a 215 x 102 x 65mm brick), the cost is quoted as higher than normal due to the bricklayers' lack of familiarity. If we are to make efforts to reduce brickwork construction costs, it is necessary either to de-skill the bricklaying process or to train bricklayers to work with different brick sizes.
It is not only brick sizes that differ. We can change the laying techniques, for example, by using thin-bed adhesive technology where a 5mm-thick high-strength adhesive is used rather than traditional cement-sand mortar.
The techniques by which clay bricks are manufactured may change with time. New design methods may demand different shapes, colours and textures but one thing is for certain - the popularity of clay as a natural building material is unlikely to diminish in the foreseeable future. It already scores well in terms of sustainability, and further innovation will improve its performance.
CASE STUDY: TRADITIONAL VALUES
Weston Homes, which specialises in restoring neglected heritage buildings to their original splendour, is turning a former hospital into the high-quality private apartments of Royal Earlswood Park.
Reached through an avenue of rare Wellingtonia Redwoods in a setting of 35ha, the Victorian building has an imposing neoJacobean facade of brickwork and stone dressings. The 109 one-, two- and threebedroom apartments are all different.Their spacious rooms, high ceilings and large windows recapture the elegance of traditional Victorian architecture.
Weston Homes chose the Milton Hall soft red brick because it was the closest match to the existing Victorian brick and it has been used extensively on a number of exterior walls that were demolished and rebuilt. The renovation is nearing completion after almost two years.
CASE STUDY: BRIDGING THE GAP
The Royal Ordnance factory in Enfield, Middlesex, has been transformed by Fairview Homes from a pre-war munitions plant into the hub of a private housing development.
The converted factory provides apartment accommodation, and the original brick has been attractively matched with facings from Hanson's London range.
Linked by two bridges, a private housing development has been completed successfully after considerable delay was incurred for essential land decontamination.
'Our partnership with Fairview and Enfield council required that Hanson would design and detail a brickwork cladding system to both parapets and abutments of the massive steel bridge structures, 'said Paul Rogatzki, Hanson's commercial design manager.
'We specified full-size Kempston Melford Yellow facings, with detail in Butterley Charnwood Natural, to clad the structures which required large quantities of matching specials.'Hanson's technical team invested heavily in time and commitment on this project, which is both aesthetically pleasing and structurally sound.The bridges are finished in reconstituted stone.