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One of my biggest financial miscalculations in my construction business happened in 2024/25. Our first project on the mainland. We wanted to buy a land. I gave the task of sourcing for the land to my 002. We finally got one in Ketu. One plot (almost 700 sqm). In a developed area. Tarred street. Sandwiched by already built houses. Land was overgrown with tall grasses but part of it visible from the road. I visited it once myself on my way from the airport. I quickly stopped at Ketu to check the land. I was ok with it. Prior to that, all the 6 projects we had done were in Ajah (Island). All one-storey buildings. 4-5 units of terraces. I had always believed lsland lands were "softer" and mainland lands "harder". All the places I had been to on the mainland had the type of soil I see outside Lagos - hard. Unlike Island that had sands. So while making mental decision to buy that land, I had assumed the land was going to be my idea of typical mainland land - hard. Different land (soil) type/density requires different foundation types. All the 6 projects we did in Ajah before then, we did raft foundation. Raft foundation is mid-way between strip foundation (for naturally strong lands ) and pile foundation (for soft lands). Pile is the most expensive, followed by raft, then strip. In short, the "softer" the soil, the more expensive foundation is (which is logical). I had assumed the Ketu land we wanted to buy would be stronger than the Ajah lands, so the worst case foundation-type scenario would be raft, the same foundation type we use for similar project size in Ajah. To be 100% sure, I called one of our technical consultants to confirm raft foundation would work on that land. He confirmed knowing the land and the area well and gave a "yes". All these happened within a week. Based on this, we went ahead and paid for the land. I also a mental calculation of what the project would cost based on my experience doing 6 of similar projects on the Island. Then, work was about to start. We did land clearing and realized the land was swampy! Totally different from my idea of mainland land in a built-up area. We did soil test and the result showed us we needed to do pile foundation of 18 meter depth with 100 pile points. In layman terms, we needed to bury well-formed steel roll into 100 points on the land, with each roll buried 18 meter deep, as foundation for the structure. To build just one-storey building. That is what you typically need to "hold" like four-storey building in an area with stronger land. That single realization cost us almost N100m more in foundation cost of that small project (5-unit terrace). Way more materials (steel, concrete, etc and special engineering contractor for piling work who comes with equipment) Image 1 below is Internet explanation of piling process and image 2 shows some foundation types I mentioned.