Testing a concept budget against a coastal benchmark
Your client wants a 6,500 m2 gross floor area mixed-use building in Mombasa: ground-floor retail and four office floors. The total budget is KES 780,000,000 including VAT, contingency and escalation but excluding land, professional fees and loose furniture. Recent comparable Nairobi office projects cost about KES 95,000/m2 excluding VAT; you assess a 12% coastal premium for corrosion-resistant materials, logistics and labour. Abnormal costs include piling estimated at KES 60,000,000 because of coral limestone voids. You normally carry an 8% design contingency, 6% escalation over the 24-month programme, and VAT at 16%. The architect's concept shows 7,200 m2, and the client asks whether the budget can accommodate it. The project is at concept design stage and the procurement route is not yet decided.
1. Test the budget for 6,500 m2 and show the build-up.
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I would build the estimate from the benchmark and then add the site-specific and financial allowances in a defined order.
Base construction cost: 6,500 m2 x KES 95,000/m2 = KES 617,500,000. Coastal premium: 12% x 617,500,000 = KES 74,100,000, giving KES 691,600,000. Add abnormal piling: 60,000,000, giving KES 751,600,000. Add 8% design contingency: 60,128,000, giving KES 811,728,000. Add 6% escalation: 48,703,680, giving KES 860,431,680. Add 16% VAT: 137,669,069, giving approximately KES 998,100,749.
The budget of KES 780,000,000 is therefore short by about KES 218,000,000, or roughly 22%. Even before VAT, the estimate is about KES 860,000,000. The conclusion is that the budget cannot accommodate 6,500 m2 on the stated assumptions, let alone the architect's 7,200 m2.
The estimate is a concept-stage estimate, not a tender price. It should be presented as a range with the assumptions and risks clearly stated, because the piling and coastal premium are the largest uncertainties.
2. Advise the client on the maximum gross floor area that the budget can support, and the main cost drivers.
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To find the affordable area, reverse the build-up, starting from the VAT-inclusive budget of KES 780,000,000. Remove VAT: 780,000,000 / 1.16 = KES 672,413,793. Remove 6% escalation: 672,413,793 / 1.06 = KES 634,352,635. Remove 8% contingency: 634,352,635 / 1.08 = KES 587,363,551. Deduct the fixed piling allowance of KES 60,000,000: KES 527,363,551. Remove the 12% coastal premium: 527,363,551 / 1.12 = KES 470,860,313. Divide by the KES 95,000/m2 benchmark: about 4,956 m2.
So the budget supports roughly 4,950 m2, not 6,500 m2. That is a reduction of about 24% from the brief. The main cost drivers are the piling, the coastal specification premium, the height and basement extent, and the retail/office mix. Piling is fixed and does not reduce proportionally with floor area, which makes the area reduction sharper.
The client should be given three options: reduce the area to about 5,000 m2, increase the budget to about KES 1 billion, or value-engineer the specification and structure. Value engineering should focus on the basement, the façade and the piling solution, not on life-safety or waterproofing.
3. Explain how you would treat contingency and escalation in the cost plan, and why they should not be double-counted.
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Contingency and escalation cover different risks and should be separate lines. Design contingency covers the cost of design development and unknown items that are not yet drawn, such as additional reinforcement, revised façade details or an unresolved basement. Escalation covers the effect of price changes over time, such as labour, steel, cement and imported finishes. One is a scope uncertainty; the other is a time-related price risk.
Double-counting occurs when a contingency is applied to an estimate that already includes a market-risk allowance, or when escalation is added to both the base cost and the contingency. The cleaner approach is to build the base estimate at current prices, add the design contingency to that base, and then apply escalation only to the projected spending profile. VAT is applied last to the total. If the programme changes, the escalation allowance must change, but the contingency should not automatically increase.
I would also distinguish risk allowance from contingency. Piling in coral limestone is a known abnormal cost, so it belongs in the base estimate, not in contingency. Unknown ground conditions beneath the piling are a risk for which a separate allowance may be justified. Presenting these lines separately allows the client to see what is fixed, what is uncertain and what is merely inflation.