@Kyt, where did you get these prices? The best I have:Y8-460, Y10-650, Y12-900. Your prices are definitely lower! hope you don't mind sharing the name of the shop.

@jaggernaut. living roomshould be 16m2, bedroom should be 2.35m x 2.35m, kithcen 1.2m by 2.4m, corridors 900mm etc. Theae are well explained in the building code available for sale at the government printer.

Thanks Bwana Architect

Greetings @Kaifastus & @rurinjaa,
Its very interesting to learn you are undertaking building works. On the issue of controlling costs, iThink sometimes we end up spending so much more on the foundation yet the loading/weight of the house may not warrant such a heavy investment.

1. My Structural Engineer friend always used to ask me, when you excavated to solid rock, why did you continue? Just anchor the building especially if its not in an earthquake prone area. This question came because contractors are prone to ask more money for excavating in rock hence more profits.
2. You can save the money you spend on extensive excavations and hardcore backfilling by suspending the ground floor slab on ground beams.

3. If the ground is firm, there is no need of excavating upto 500mm and backfilling. Of course you have to agree with the Structural Engineer. But its important to ask these questions as you undertake this journey.
4. Have a program of works that fairly guides the whole process. This will save you on labour cost & planning + reduce fatigue.
5. Lastly, what is the floor area of your project? Just add top floor area and ground floor = xy
You can divide the total money you have already spent by this area to get a rough idea what would be your total spend. If you had, say projected to spend Ksh 20,000 per sm and already you are at 15,000/sm...it suggests to you the project should be at 75% completion roughly. Its good practice to keep an eye on the numbers.
-Cheers
Qs.Nahinga/Ujenzibora