@jamplu, the cost of walling using reinforced concrete is twice the cost of walling with stone, at around kes 2,500 per m2. The cost of using fibre cement panels, similar to the ones produced by NHC is also more costly than stone, at kes 1,800 per m2 compared to stone at kes 1300 per m2. Only ssb soil blocks are cheaper but have disadvantages eg high failure, not structural, wears out easily etc etc

i have designed several in Ruiru town using this method but only for industrial type and ware house type structures. These are useful in structures that should retain heavy forces, need extra security etc etc, ot for residential buildings. Where is the site to be located? If in an expensive area, then the high cost of construction will be absorbed by the high selling price.

Also, maybe he has a way fo importing cheap cement and steel so his costs are lower than market rates eg the highway and bypass roads contractors.