Brick to transform slums?

The Cape Town Building Centre will this month feature a stand promoting a new concrete block-making system that has the potential to make building a lot simpler, according to Mike Grose, the Chief Executive of Technical Finishes, which supplies the bonding agent for the blocks.

The system, to which the inventor and developer, Andre Esterhuizen, has given the name "Stumbelbloc", will enable people in outlying areas, especially those in small rural communities, squatter camps, on farms or indeed in any area to which the delivery of concrete blocks might be prohibitively expensive to build for themselves at greatly reduced costs.

Stumbelbloc supplies the customer with very strong plastic moulds into which the freshly mixed concrete for the blocks is then poured and compacted. The mould is stripped after 48 hours and the block is left to cure for seven days. The operation can be carried out almost anywhere provided that there is water, cement, sand and stone available and provided that the curing can take place in the shade.

The moulds sell at R198 each, VAT inclusive, with discounts applicable for large orders.

The defining features of the new blocks, says Esterhuizen, are, firstly, that they are hollow core and therefore ideal for home building as they reduce heat transmission and, secondly, that they have seven male/female indentations top and bottom which ensure that they interlock vertically with complete uniformity and do not require special blocks to go around corners.

The ability to lock the blocks together imparts considerable extra strength to the wall structure and this is enhanced by the base of the blocks being dipped in a Technical Finishes product known as Blockgrip. This is a quick hardening cementitious product that sets in three hours and strengthens the joints between the blocks.

The system does away with the need for conventional cement mortar ("dagga") bonding and as a result makes for far faster building. Once the base course has been accurately laid, the blocks can be laid by unskilled workers after minimal training. What is more, they can start anywhere on the wall — two or three can work on the same course simultaneously because the blocks will always fit together.

"It is," says Esterhuizen, "almost impossible to lay these blocks incorrectly. If a block is not laid as designed it simply will not fit. In this respect the system is similar to Lego, the children’s building blocks."

Two types of block are made: the full size block measures 398mm x 178mm x 198mm. The half block is to ensure stretcher bonding as in conventional brickwork.

Esterhuizen stresses that, as the blocks are all handmade and as they do not call for a big capital investment, they are ideal for use in remote areas where job creation needs boosting and deliveries are expensive. They are also, he adds, ideal for situations where the builder wants to conform to "green" requirements: the manufacturer requires no power, minimal transport and makes little mess.

Blocks laid at great speed

All those who have observed the operation in use, says Jamie Heathcote-Marks, General Manager of the Building Centre in Rondebosch, have been extremely impressed by the speed at which blocks can be laid.

"In one case," he says, "a 2.4m high column was erected in less than three minutes. This is a fraction of the time that would be required for conventional building with mortar."

The block making, too, says Heathcote-Marks, is speedy; one person can make as many as 50 blocks in a single day.

A demonstration room (with a tiled roof) has been built at Technical Finishes’ Epping factory to demonstrate the new system. On this a three man team with no previous experience of the work were able to erect 30m² of walling, including a door and window, in four hours. This time, says Esterhuizen, could, in fact, be halved with a little practice.

The blocks are load-bearing from the moment they are laid. Provided good materials are used in the concrete; strengths of 9MPa can be achieved quite easily. (A standard double storey home requires block strengths of 7MPa.)

Grose says that there will be many small housing and building teams, farmers, township entrepreneurs and many hundreds of home handymen who will welcome this opportunity to produce a well finished, accurate block themselves at low cost.

"The new block design is perfectly adapted to the smaller operator who wishes to use his own labour force and to keep his costs substantially below conventional building methods," said Grose. "Now you can build your own boundary walls, columns, additions, garages or even houses using this revolutionary system."

For further information contact Andre Esterhuizen on 083 228 8036 or Mike Grose on 021 535 4455.

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