A bill of quantities is the house written as a list of things you will buy. Read top to bottom it tells you, in order, what money does: it goes into the ground, then up the walls, then over the roof, then onto the surfaces you actually touch. You do not need to be a quantity surveyor to use one. You need to know what the rows mean and what the number at the bottom is and is not.
What an elemental estimate is
The cost plan attached to a Chimbuko set is an elemental estimate. It takes the real quantities the drawing produces — square metres of wall, cubic metres of concrete, linear metres of skirting — and prices them against current Kenyan rates, grouped by element. That is a level of honesty above a rate per square metre, which is a rumour, and a level below a contractor’s priced tender, which is a commitment. It is the right instrument for two jobs: deciding whether you can afford this house, and checking whether a quote you have been handed is sane.
Walking the elements
- Substructure. Excavation, foundations, ground slab. Invisible when finished and unforgiving if wrong. It moves with the soil and the slope, so it is the line most sensitive to your actual plot.
- Superstructure. Walling, columns and beams, any suspended slab, the staircase. This is where a maisonette collects its extra cost and a bungalow collects its extra roof.
- Roof. Structure, covering, rainwater goods. A hip roof buys more timber and more tile per square metre of house than a flat parapet roof buys concrete — which is why the two typologies price differently even at the same floor area.
- Openings. Doors, windows, ironmongery. A deceptively large number, and the one homeowners upgrade most often after seeing the renders.
- Finishes. Plaster, screed, tiles, paint, ceilings. The most elastic element in the whole bill: the same house can be finished at two very different prices, and this is where you flex if the total frightens you.
- Services. Electrical installation, plumbing and drainage, fittings. Follows the electrical and drainage schematics in the technical pack.
- External works. Paving, boundary wall, gate, septic, landscaping. Frequently left out of cheap quotes and then discovered as an emergency.
Prelims and contingency, explained
Preliminaries are the cost of running the build rather than the cost of the building: site setup, hoarding and security, water and power on site, insurances, the contractor’s supervision and overhead. They are real, they are legitimate, and a quote that omits them is not cheaper — it is incomplete, and the money will appear later with less warning.
Contingency is money set aside for what the drawing cannot know: rock where you expected soil, a rate that moves, a decision you change your mind about. It is not padding and it is not the contractor’s bonus. Treat it as unspent until the build is finished, and be honest with yourself that on most Kenyan residential builds some of it gets spent.
Why the estimate carries a date and a band
Every Chimbuko cost plan states its rates version and carries a ±10% band. Both matter. Rates move — cement, steel and labour are not fixed — so an estimate without a date is an estimate without a meaning. And the band is an admission of what a drawing-stage estimate can honestly claim: the quantities are firm because they come from the geometry, the prices are indicative because nobody has tendered yet.
Read the band the sober way round. Budget against the top of it, not the bottom. If the top of the band is affordable, the house is affordable.
Using it against a fundi or contractor quote
Put the two documents side by side and compare element by element, not total to total. Three things will show up almost immediately: elements the quote has left out, elements priced far below your estimate because the specification has quietly dropped, and elements priced far above because of an assumption nobody stated. Any of those is a good conversation. None of them is an accusation — you now simply have the vocabulary to ask.
And ask for the quote in the same shape. A contractor who can price your BOQ line by line is a contractor who has read your drawings.
What it is not
It is not a quotation. Nobody has agreed to build your house for this number, and it does not bind anyone. It is the honest arithmetic of your drawing at today’s rates — which is exactly what you need to decide, to budget, and to tender without being taken for a ride.