Why two identical-looking houses can differ by 40% in price, and how to tell whether a cheap quotation is efficient or incomplete.
Why nobody can quote you a price over the phone
The first question almost every client asks is what it costs per square metre. It is a reasonable question, and any contractor who answers it confidently before seeing your drawings and your plot is guessing — or quoting a number low enough to win the conversation and high enough to be revised later.
The reason is that the square metre rate is an output, not an input. It falls out of the specification, the ground, the access and the programme. Change any one of those and the rate moves substantially.
The five things that actually move your number
In our experience these account for most of the variation between two houses of identical floor area:
- What is under the plot. Black cotton soil across much of Nairobi and Kiambu swells and shrinks with moisture. Building on it without allowance produces cracked slabs within a few years. Dealing with it properly — deeper excavation to stable ground, or a foundation designed to span it — is a substantial cost that appears before anything is visible above ground.
- The specification, especially the finishes. Structure is relatively inelastic; finishes are not. Floor finishes, sanitary ware, joinery, ironmongery and aluminium can double between a sound basic house and a high-specification one, with no change to the drawings at all.
- Storeys and shape. A two-storey house of the same total area costs less per square metre than a bungalow — you build one roof and one foundation instead of two. Complex plan shapes with many corners cost more than simple ones, because corners are slow.
- Site access. If a ready-mix truck cannot reach the pour, concrete gets mixed on site or barrowed, and both cost time. A plot down a narrow murram lane genuinely costs more to build on than one on a tarmac road.
- How long it takes. Preliminaries — site establishment, supervision, security, fencing, plant hire — run for the duration of the project regardless of what is being built. A job that drags for eighteen months instead of ten carries eight extra months of these.
What the cheapest quote usually leaves out
When one tender comes in far below the others, it is worth finding out why before celebrating. Compare the scope line by line rather than the bottom line. The items most often missing:
- Site clearance, excavation to a realistic depth, and cart-away of spoil
- Septic system, soak pit and site drainage
- Boundary wall, gate and perimeter security
- Water storage, tank base and plumbing to the mains or borehole
- Electrical connection, meter and any transformer contribution
- External works — driveway, paving, landscaping, external lighting
- Professional fees and county approval costs
- A realistic contingency for what a drawing cannot predict
A quotation that omits several of these is not cheaper. It is smaller, and the difference reappears later as variations at a point when you have no leverage to negotiate them.
Bill of quantities versus lump sum
Insist on a measured bill of quantities. It lists every item of work with a quantity and a rate, so you can see what the roof costs separately from the foundations, compare tenders on identical scope, and price a change fairly when you want one.
A lump-sum quotation on a single page gives you none of that. You cannot tell what was included, you cannot compare contractors meaningfully, and when you change your mind about a finish there is no agreed rate to price it against.
Budget for the things that are not construction
Clients routinely fund the building and forget everything around it. Set money aside for professional fees, county approvals and NEMA where applicable, utility connections, and a genuine contingency. Then add the cost of the time itself if you are paying rent or servicing a loan while you build.