Butterworth and Foster conducted an extensive survey of continental brick making practice in the mid-1950’s and horizontally and vertically perforated bricks were made on a pilot scale in the BRS laboratories, which became BRE.
Perforated bricks were not new to the UK. Standard bricks with a perforation proportion equal to about 15 per cent by volume were made by a few brickworks. The properties of the bricks used were similar, and the real reason for perforating the bricks was to overcome manufacturing difficulties in making wire cut bricks from certain clay types.
It had also been argued that solid bricks were unnecessarily strong and furthermore that the introduction of voids improved their poor thermal performance. Much effort was made into developing patterns of new bricks which gave the optimum in thermal insulation and strength. This was done while still enabling the building of rain-resistant walls.
There were two types of perforation tried, horizontal perforation (H) and vertical perforation (V). Both had their merits, but vertically perforated appeared more promising. Several patterns were developed, and the final version provided bricks, including mortar joints, in a module of 9 inches. x 9 in. x 3 in. As a result, the wall appeared as solid as a brick wall due to its perforations, it weighed only slightly more than a brick made from the same clay, but its volume was equal to two standard bricks. Average weight of the V brick was 8 lb 11 oz. With a standard brick of the same clay weighing 7 lb 2 oz.
The bricks were laid with a divided mortar joint to give what was effectively a cavity wall with narrow ceramic ties. It was demonstrated that a wall of BRS V bricks could be laid 30 per cent faster than a facing brick/ cavity/ common brick wall. However, it was about the same time as a facing brick/ cavity/lightweight concrete-block wall. The bricks were not easily cut so either solid bricks or special ‘L’ shaped bricks were used for corners. Much guidance was produced by BRS covering planning to use the bricks particularly relating to dimensional co-ordination and including the recommendation to avoid ‘fussy details’.
During the development period, BRS V bricks were demonstrated at exhibitions and used to construct a considerable number of buildings including flats, houses and schools. A variety of bonding and other problems arose in these buildings and solutions were developed. Brick makers took up manufacturing with one plant due to start producing in 1962 and a second shortly after.
The need to improve thermal insulation of walls led to the introduction of lightweight insulating blocks and their use in a facing brick/cavity/insulating block wall became almost universal. The V brick could not offer these benefits and faded from the scene.
However other countries still recognised the advantages of perforated clay blocks and the Prince’s Natural House on the BRE Science Park at Garston has been constructed using imported blocks.
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