The South African Stumblebloc system makes it easy for anybody to build at twice the speed of traditional building methods, using unskilled labour, without any external power, and at up to half the cost of a traditional building.
Stumblebloc is based on a mould set-up, with which hollow core blocks can be made on-site within 48 hours. Stumbelbloc’s plastic moulds are simply filled with a concrete mix and left to dry.
The building itself involves simply stacking blocks on top of each other.
The finished product is a very accurate, hollow-core block with a special interlocking shape which, along with the thin-bed glue mortar, called Blockgrip, makes for quick, easy and cost-effective building.
A 16m x 2m wall can be built from foundations within 40 minutes, and a small house to roof level within two days. The system requires no lintels and the complete structure can assume full load-bearing immediately.
The South African Bureau of Standards’ strength requirement for building blocks is 3.5MPa – the standard Stumbelbloc has been tested at 6.8MPa.
The simplicity in design means that transport and production costs, and carbon footprint, are kept to a minimum. Costs
The material cost for manufacturing a standard block is R4.50 ($0.65) in Cape Town, South Africa. There is also a saving in the cost of transport if the blocks are made on-site, which (in Cape Town) is about R3 ($0.42) per 100km per block.
An advantage of the Stumbelbloc system is that the material used in production can be varied in accordance with local requirements, as well as required strength.
An average unskilled labourer can make up to 50 blocks per day, using hand-mixing. With a few basic tools and electric power, a small production unit of three labourers can make up to 250 blocks in a day. The system can obviously create employment and empower communities.
The cost of each (full) mould is R174 ex VAT ($24), ex-factory in Cape Town. Half moulds are also available and bulk packs can be purchased at a discount.
To properly build with this system, Blockgrip (a proprietary additive for cement) must be bought. This means that much less cement is used than in normal building. It also allows for extended movement of the blocks before the solution dries. The Blockgrip is sold in a 1kg bag (costing about R100 ($14)), which is added to a bag of cement and one level wheelbarrow of sand, to lay 600 blocks. A small house would use about 1,200 blocks.
Both worldwide patents and design rights have been applied for, for both the moulds and the blocks.
Andre Esterhuizen, CEO of Stumbelbloc, is currently appointing agents in the rest of Africa. Agents need to find enough demand to buy a container-load of moulds (1,750, costing about $30,000 ex transport); they can apply local pricing for their customers. Appointed agents must also come to South Africa for training. They will also need to sell the Blockgrip as an ongoing consumable.Walls for a 42m house erected in six hours
Claims by Stumbelbloc that its system can cut building times by up to 50% were verified recently when a team of one bricklayer foreman, two handymen and four labourers completed the blockwork of a two bedroom 42m cottage in Cape Town (pictured above) in six hours.
Andre Esterhuizen, CEO of Stumbelbloc, invites all involved in building, especially those in low cost and conventional housing, to come to the indoor riding school at Joostenbergvlakte, near Cape Town, to inspect the finished home. Alternatively, he said, they can view how the six-hour construction went by watching Stumbelbloc’s video on the website: www.stumbelbloc.com .
Esterhuizen said that although the total cost of the completed cottage was only R57,000 ex VAT ($7,993), “the quality of the structure is far superior to that of normal low-cost housing standards, as confirmed by all who have seen it”.
“Also, only six bags of cement were needed to bond the brickwork and only 0.46 cubic metres of Skimplaster rendering were needed to render the exterior of the house – at a far lower cost than conventional plaster. And the rubble created by the operation amounted to only two wheelbarrows. Furthermore, no electricity was needed during the building process.”
The 15kg 200mm x 400mm Stumbelbloc block weighs the same as a 140mm x 390mm block and is denser because it is wet-cast.
“This density enhances the block’s thermal qualities which are already at a high level as it has cavities which are kept open during the construction process. Thermally, therefore, it performs in a similar fashion to a cavity brick wall. As all piping and cabling can be fitted into the cavities, no cutting of the walls are necessary.”
Esterhuizen: Tel +27-83-228-8036;email@example.com