There is no definite cost as it depends on management of the production process (labour, materials and machine efficiency). If production is done efficiently and the soil is sourced from site, the cost could be about Ksh.16 per block; with imported soil the amount could go as high as Ksh.35.

A house built using ISSB is durable and can last for over 60 years subject to use of suitable materials, proper workmanship and regular maintenance practices

Currently the machine is being offered for free as an incentive to accelerate uptake of the technology. However the client is expected to cater for the machine operating costs i.e. fuel, routine maintenance, towing charges, labour and security of machine among others.

Yes, they can be applied in the construction of buildings up to 3-storeys as guided by a qualified structural engineer. The blocks could also be used as infills for high rise framed structures.

ISSB are strong with minimum compressive strength of 2.5Mpa as per KEBS standard. The strength can however be increased depending on the required load bearing.

There are approximately 37 blocks in one square meter of wall.

We just facilitate by providing the necessary technical assistance through training on machine operation, ISSB production and construction procedures.

NO. Black cotton soil is not viable as it contains highly reactive clay and the blocks will crack when they dry. Black cotton soil also contains high amounts of organic material which is not suitable for block production. However, sandy loam soil is preferred. Generally, you can use soil with 15-35% clay and silt content.

“Green” (fresh) ISSB are stacked and covered with black polythene sheeting to avoid moisture loss. The blocks are then watered daily to create a green house effect, allowing the cement to harden and the blocks to strengthen. It is recommended that one uses 1000 gauge black polythene sheeting for curing. Cure your ISSB for a minimum of 7 days and allow the blocks to dry for another 14 days before construction to ensure you have strong good quality blocks.  

Construction process should commence after 21 days. However, cement gains full strength in 28 days.

The colour of the blocks is determined by the colour of the soil being used to produce the blocks.

Yes, one has to use cement and/or any other available binder.

It can affect if construction blocks are not of good quality. The surface can also be protected against adverse effects of rain and strong winds by:

• Applying proper finishes on block surface of exterior side of the building using Crown’s “Permacote Ultraguard with Silicone” paint to protect block surface from rain water penetration.
• Plastering of gable sides as well as skirting of up to 2 to 4 courses of block as may be appropriate.

Yes, as long as the client mobilises local labour force for training. However, priority is given to community groups.

There is a block tester to measure compressive strength of ISSB after curing.

Yes. The standard was developed by KEBS in 1993 and is referred to as KS 02-1070 on use of stabilized soil blocks.

For single houses and community projects, a labour based contract using trained fundis could suffice. But for large projects, use of professionals is necessary. It is critical for clients to liaise with County Directors of Housing to get contacts of trained fundis in various counties. A list of currently identified ISSB professionals is provided in the Ministry’s website under “Inventory of ABMT”.

• Dishonesty by some clients who deviate from the recommended ratios that compromise quality
• Failure to seek technical advice during construction stage.
• Failure to clean machines after daily production leading to rapid wear and tear.
• Lack of routine maintenance of borrowed machines.

• Using wrong towing equipment leading to machine damage.
• Failure to carry out block-testing in order to determine compressive strength for quality assurance.

Small scale application of ISSB technology poses minimal negative effects to the environment. In most instances the resultant burrows can be put into others uses including: development of septic tanks, pit latrines, foundation of buildings, compost manure sites, tree growing, farm gardens, water pans, fish ponds, rubbish pits; among others.

You cannot expressly state the nature of the soil. Officers from the housing office, accredited ISSB professionals, technicians and artisans should visit the site and carry out suitability test for your soil.

• Accredited ISSB professional is a registered person or non-registered persons who is nevertheless trained and backed by demonstrable working experience in ISSB and has practiced and implemented ISSB projects to satisfactory levels in management of training, production and construction processes.
• Accredited ISSB technician is a person with built-environment technician certification or any other person who is nevertheless trained and backed by demonstrable working experience in ISSB and has practiced and implemented ISSB projects to satisfactory levels in supervision of training, production and construction processes.

• Accredited ISSB artisan is a person with built environment artisan certification or any other person who is nevertheless trained and backed by demonstrable working experience in ISSB and has practiced and implemented ISSB projects to satisfactory levels in production and construction works.