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Theme: bricks and blocks

During the past century, the role of bricks has changed from structural to protecting the real supporting structure within - the blockwork. Consequently, the focus for brick manufacturers has switched to appearance, while innovation in blocks is geared to

You don't necessarily expect stuff that is basically processed dirt to have properties such as lusciousness and warmth of texture and delight. The stuff, of course, is brick and the bit about lusciousness and delight isn't always true. We tend to think of brick as brickwork - that is, lots of individual bricks, of a size a brickie can pick up with one hand and butter with the other, all visually separated by beds and perpends of mortar.

But it is not as straightforward a business as that might suggest. There are half a dozen common bonds that affect the appearance of a brick structure. The colour of mortar has, relatively recently, been recognised as having a major effect on the appearance of brickwork. The bricks themselves come in a bewildering array of textures and colours - some of which have little to do with the natural moulded surface or colour of the original clay. Sometimes the clay is actually concrete.

Until the middle of the last century a brick wall was a structural thing. Now it is invariably an outer skin protecting the real supporting structure of blockwork or steel or timber studding from rain and the occasional bump. And it is said that bricklaying has been deskilled, along with the rest of the building trades.

So there is as much scope for getting brickwork wrong as there is for getting it beautifully right. Architects regularly grumble to each other about how impossible it is to get decent brickwork these days. Ancient Sumerian architects probably did, too. But manufacturers want to nail the myth that there is a shortage of craftsmen. They bring out various figures to prove that the number of bricks produced per head of bricklayer hasn't really changed in decades.

Nevertheless, in this post-Egan age of construction, many people find quaint the idea of others working up on scaffolding with plumb bobs and lines and hawks and trowels and hods and mortar and piles of bricks - as they have done since the time of ancient Egypt and Mesopotamia. If factory production means greater accuracy, they say, then why not think the impossible and consider factory production of brickwork, especially when it has become a cladding material, or 'brick veneer' as Australian housebuilders aptly labelled it 50 years ago.

The old Modernist moral certainties about truth to materials, which used to hinge specifically on materials such as brickwork, have been on shaky ground for some time. It is interesting that stack bond, the bond that makes no pretence of working as a knitted surface, has appeared in a number of recent projects.

Market-aware brickmakers have to be constantly on their toes with new brick colours and textures. Blockley, for example, has just launched a new range of blue bricks - blue in the clay sense rather than glazed.

They are a response to calls for decorative courses and cappings, and for bricks to use in contrasting courses. Ibstock has introduced a new production line at its Leicester plant that enables it to continue making extruded bricks and what are known as softmud products. The process will allow runs of different finishes, colours and textures, all from the same clay source. At the same time, the company is adding to its existing Leicester Red and Dorset Stock ranges of sand-faced, spray-coloured bricks, together with the new Arden range, which has a waterstruck surface with a smooth finish and sharp arrises.

Hanson has introduced Wilmslow Antique, an extruded wirecut, whose texture is created by applying slop clay to the smooth face, then sand and stains. But the widest chromatic range, rather than mere variations on earth colours, is to be found in the calcium-silicate efflorescence-free bricks from manufacturers such as Hyde Oak, which offers 20 different colours.

On the other hand, bricks can sometimes be tiles. Mathematical tiles became common in the 19th century, probably originally as a way of giving timber buildings a higher status by casing them in what appeared to be brick. The shaped overlapping tiles, one brick or a half-brick wide depending on the bond used, were nailed on to horizontal battens, in the same way as tile hanging. The twist at the end is that the open joints were pointed. The result was quite convincing and even now, perhaps 150 years later, it is only tiny clues, such as at the ends of walls, that alert you to the fact that a house might not be solid brick.

Modern versions include Redbank Lockclad, Moeding Alphaton Terracotta Rainscreen System from James and Taylor and Baggeridge-owned Corium, which makes large-format, open-joint staggered tiles as well as brick-sized tiles that can be pointed or not. Corium's fixing technique is more hi-tech than traditional mathematical tiling. It involves rows of interlocking steel sections into which brick tiles are simply clipped and later pointed using pre-bagged Corium mortar and a pump system. This can also be assembled as panels in a factory.

Now that an external corner detail has been developed, the great advantage for latter-day mathematical tiling is that it is lightweight. At south London's Lambeth College, the system was used recently to clad a new lift shaft in a tight internal courtyard. Reid Architecture specified retrofitted, and therefore lightweight, chimneys in a conservation area for the Wilbraham Hotel, made using the Corium system.

An inversion of this is Ibstock's Tilebrick, which seeks to simulate tile hanging. The basic unit - around half the length of a traditional brick and as deep - has a face that incorporates an overhanging lower section.

This sits over the top of the Tilebrick below and, in a complete wall, looks exactly like the real thing. Claimed benefits are longevity and integrity, there being no battens and nails to deteriorate, and no tiles to break, as well as lower installed cost. It also means a house can be built using the same bricklayers. Bovis Homes has tried them out, as has the University of Greenwich at a centre in Dartford.

Supporting act Metal lintels go back a surprisingly long way and were preceded by timber. It is true that the traditional high-status way to span a gap in a wall was to use an arch - even if it was the Georgian flat arch, which deployed soft bricks (rubbers) that were rubbed together on site until they lay closely in their slanting formation before being installed using very thin beds of mortar. This is probably a lost skill for the very good reason that it takes a long time and lintels are now universal.

Ibstock has now introduced a prefabricated flat arch called the Easy-Arch, which is actually a window-wide lightweight aggregate block with slanting brick slips adhered to the face ready for pointing. Similar elements are available from other manufacturers.

Lintels can be quite sophisticated, with matching pre-formed cloaking and weep holes. They can also make the creation of unusual shapes, such as bulls-eyes and big arches, relatively simple. Catnic has been responsive to the market and now offers more than 260 special lintels, including big spans, lintels for chamfered bricks, and secret-toe lintels for cant bricks. They are hot-dip galvanised after fabrication and given a final polyester powder coating.

Innovation Even in non-vandal-prone places you see garden walls whose coping courses have worked loose - not surprising when they often sit on a damp-proof course. Ibstock has introduced what looks like a reverse lintel. Its lower flange sits on the DPC membrane course and is held in place on either side by the next course of bricks. The upper part of the 'lintel', called a Caplock, has an open U-section over which slides a special double-width, roundcornered coping brick, whose underside locks on to the U-shaped profile.

Ibstock has also reintroduced the Universal Joint, now called the Easy Angle. It consists of one brick with, in plan, a concave end and another brick, pinched in the middle and then rounded. Together, they form a variation on a ball-and-vestigial socket, which provides an interesting way of turning a non-right-angle corner - as, for example, in a number of conservatories. The alternative would be to have specials made or to fudge the corner and allow the corners of alternate bricks to project. The base and head of the Easy Angle corner can be finished neatly with a special tool known as the Elephant's Foot.

On the block More than 60 per cent of all blocks are made from aggregate concrete - in the ranges from dense to lightweight - and 70 per cent of those used in new houses. So prevalent is brick/insulation/block construction that the originally PR-spun description 'masonry construction' has become the accepted description. This is not the place for a timber/steel frame versus blockwork debate.

Each system has its virtues and, in England at least, blockwork has the advantage of being the customary way of building the inner leaf. Blocks used to be a little heavier than bricks, often needing two hands to lift and perhaps twice the size. Bricklayers had to work out new techniques for handling blocks and laying them. As building regulations changed over the years, so did the weight and dimensions of blocks and it was sometimes forgotten that ordinary humans had to lay them. Now Construction (Design and Management) (CDM) regulations about the weight of items that are lifted repetitively have brought about smaller dimensions for dense blocks - such as the 140mm Easilift block from Hanson.

Part of this general move in the direction of making life easier for builders is Thermalite's Tongue and Groove Trenchblock. At less than 25kg, the block is a legal one-man lift but it also has integral handholds. As the name suggests, these blocks are slotted end to end and so have no perpend mortar. They are also laid using the new thin-bed mortar technique.

Hanson, like some of its rivals, is also engaged in research into the use of secondary aggregates such as slate- and chinaclay waste to reduce the amount of gravel extracted. The company has been trialling the use of shredded tyres, pelletised plastic ground glass and other potentially recyclable materials. Research effort is also going into new lightweight aggregates and different configurations of hollow and cellular blocks.

Aggregate Industries' Charcon has developed a paving block and kerbing, the EcoPave and EcoKerb, whose aggregate includes Cornish granite, copper slag, china clay stent, local aggregates and recycled water. The final appearance is said to be granite-like with a black fleck. Charcon is going quite a long way with recycling and uses filters in the batching plant made from recycled paper. The company is also looking at ways of recycling shrink-wrap.

Blockley has introduced a new twist on paving with its permeable clay pavers. Each brick-sized block has two square holes in it, allowing surface water to drain away immediately to, perhaps, local underground stormwater storage. There are four colours, including red and charcoal.

Blocks on show For years architects have been using fairfaced block work internally (and sometimes externally) as part of a found/industrial aesthetic. The results were often disappointing. Now the quality of blockwork makes it a viable choice. Thermalite's SmoothFace aircrete blocks are made from 50 per cent pulverised fuel ash, which, apart from its thermal performance and light weight, can be left fair-faced or painted.

Along with Thermalite, Celcon is almost a generic name for aircrete blocks, a technique particularly suited to fairface accuracy. A new product is literally an extension of the existing range, being 610mm long rather than 440mm; the other dimensions - 215mm high and thicknesses up to 355mm - remain the same. Celcon has also brought out its Jumbo Plus block, designed for use with the Celcon 3mm thick Thin-Joint system. It, too, is 610mm long but higher at 270mm and is available in thicknesses from 90mm to 140mm. Mostly the block remains under the 20kg single-person handling limit.

Check it out The new standard for clay bricks, BS EN 771-1 is introduced at the end of October. It will change little apart from the way manufacturers describe bricks. Ibstock has a hotline at 0870 903 4017.

Ancon 1500 Baggeridge 1501 Blockley 1502 The Brick Business 1503 Catnic 1504 Celcon 1505 Charcon 1506 Hanson 1507 Hyde Oak 1508 Ibstock 1509 James and Taylor 1510 Redbank Lockclad 1511 Tensar 1512 Thermalite 1513 Topblock 1514 READER ENQUIRIES Sophisticated but primitive: because bricks are rectangular, it is easy to forget that they are moulded clay and can be any shape at all. This unwitting version of the Primitive Hut at this year's Chelsea Flower Show might well have had the Abbé Laugier's blessing. Or not. The clay is the same as is used in Baggeridge's Marlborough smooth reds.

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