One of the most confusing experiences for a homeowner or property developer is receiving several contractor quotations for the same house and discovering that the prices are dramatically different.

You may have the same architectural drawings, the same number of bedrooms, and the same project location. Yet one contractor quotes KSh 12 million, another KSh 15 million, and another KSh 18 million.

The immediate question is usually:

“Who is overcharging me?”

But the difference does not necessarily mean that one contractor is dishonest or that another is automatically giving you a better deal. In many cases, the real issue is that the quotations are not based on exactly the same scope, quantities, specifications, and assumptions.

This is one of the reasons a properly prepared Bill of Quantities (BOQ) and professional tender analysis are so important.

A BOQ provides a structured basis for pricing construction work, allowing contractors to price defined quantities and descriptions rather than making their own assumptions about what the project requires.

The Same Drawings Do Not Always Mean the Same Price

Architectural drawings show the design, but a contractor still has to interpret the scope of work, specifications, quantities, construction methods, preliminaries, and other requirements when preparing a quotation.

If different contractors make different assumptions, their final prices can vary considerably.

For example, imagine a house requiring 600 square metres of floor tiling.

One contractor may price standard ceramic tiles at KSh 1,500 per square metre.

Another may allow KSh 3,000 per square metre for a higher-grade porcelain tile.

Both contractors have priced “floor tiles,” but they have not priced the same specification.

The difference is not necessarily in the contractor’s markup. It may begin with the specification itself.

1. Bill of Quantities Gaps

A major reason for price differences is what is included, or excluded, from the contractor’s pricing.

A detailed BOQ breaks the project into measurable work items, allowing contractors to price the same quantities and descriptions. This creates a much fairer basis for tender comparison.

Without a comprehensive BOQ, contractors may interpret the drawings differently.

One contractor might include:

• External works
• Drainage
• Water tanks
• Kitchen fittings
• Painting
• Site clearance
• Temporary works
• Certain electrical installations

Another contractor may assume some of these are excluded or will be priced separately.

The result?

Two contractors can genuinely submit very different prices for what the client believes is “the same house.”

This is why comparing only the bottom-line figure can be misleading.

2. Material Specifications Can Change the Price Significantly

The word “tiles” does not tell you enough.

Neither does “doors,” “windows,” “sanitary fittings,” or “roofing.”

Construction materials come in different grades, brands, sizes, finishes, performance levels, and installation requirements.

Consider windows.

A quotation may simply state:

Aluminium windows — KSh X

But what type of aluminium profile is being used? What glass specification? What thickness? What colour or finish? What hardware?

The same applies to roofing, sanitary fittings, cabinetry, electrical fittings, ironmongery and finishes.

A BOQ and its accompanying specifications should define what is required so that contractors are pricing against a common standard rather than making independent assumptions.

In Kenyan tender documentation, BOQs commonly contain descriptions and specifications that establish the basis on which work is to be priced.

3. Provisional Sums Can Make One Quote Look Cheaper

Another source of confusion is the Provisional Sum.

A provisional sum is an allowance included for work or circumstances that cannot be sufficiently defined or measured at the time of tender.

For example, certain specialist works, unforeseen conditions, or elements whose final requirements have not yet been established may be provided for using provisional sums.

Kenyan public procurement documentation, for example, recognises provisional sums as allowances for physical contingencies and potential price-related uncertainties, with their use and authority normally defined within the contract documentation.

The important point for a client is this:

A provisional sum is an allowance, not necessarily the final cost.

Suppose Contractor A has a KSh 500,000 provisional sum for a particular item, while Contractor B has allowed KSh 1 million.

Their tender totals will immediately look different—even before considering the contractors’ actual pricing for the defined works.

This is why a QS must look beyond the grand total and examine what makes up that total.

4. One Contractor May Have Priced More Completely

Sometimes the contractor with the higher quotation has simply allowed for more of the work.

Imagine three contractors submit the following:

At first glance, Contractor A appears to be the obvious choice.

But after analysing the quotations, you discover that Contractor A has excluded external works and certain finishes, while Contractor C has included them.

The apparent KSh 3.6 million difference is therefore not a true comparison.

If the excluded work is eventually required, Contractor A’s final cost could move much closer to, or even exceed, the other quotations.

The lowest initial quotation is not always the lowest final cost.

5. Labour, Overheads and Construction Methods Differ

Contractors also have different business structures and operating costs.

Their pricing may reflect differences in:

• Labour rates
• Productivity
• Plant and equipment
• Site supervision
• Transport
• Site establishment
• Overheads
• Profit margins
• Procurement arrangements

Two contractors can therefore price identical quantities differently even when they are working from the same BOQ.

This is where tender analysis becomes important.

The objective is not necessarily to find the contractor with the lowest rate for every individual item. It is to understand whether the overall pricing is reasonable, complete and commercially sustainable.

6. An Extremely Low Quote Can Be a Warning Sign

A quotation that is significantly below the others should not automatically be celebrated.

It should be investigated.

Why is the price so low?

Has the contractor:

• Missed items?
• Used different material specifications?
• Underpriced certain trades?
• Made unrealistic assumptions?
• Excluded important works?
• Used unusually low labour or material rates?

A significantly low tender may create problems later if the contractor attempts to recover the difference through variations, substitutions, claims, or other adjustments.

The question should therefore not simply be:

“Who is cheapest?”

It should be:

“Why is this contractor cheaper?”

7. This Is Where the Quantity Surveyor Becomes Important

A Quantity Surveyor helps turn several seemingly incomparable quotations into a meaningful comparison.

The QS can analyse the tenders against the BOQ and identify:

• Missing items
• Major rate differences
• Specification discrepancies
• Abnormally high or low rates
• Provisional sums
• Exclusions
• Arithmetic errors
• Differences in preliminaries
• Potential risks within the tender

The purpose is to establish whether contractors are actually competing on the same scope of work.

In Kenya, the BOQ also forms part of the documentation used in construction project registration, with the National Construction Authority requiring a BOQ summary page duly signed and stamped by the Quantity Surveyor among the project registration requirements.

A Simple Example

Consider a homeowner who sends the same house drawings to three contractors.

They receive:

Contractor A — KSh 13.8 million
Contractor B — KSh 15.4 million
Contractor C — KSh 17.1 million

The homeowner assumes Contractor A is offering the best deal.

The QS analyses the quotations and discovers:

• Contractor A has excluded external drainage.
• Contractor A has allowed a lower specification for floor finishes.
• Contractor A has a significantly lower allowance for electrical fittings.
• Contractor B has included the required specifications.
• Contractor C has included the same specifications as B but has higher preliminaries and overheads.

Suddenly, the comparison becomes much clearer.

The client is no longer comparing KSh 13.8 million against KSh 17.1 million.

They are comparing what each contractor is actually offering for the money.

That is a completely different decision.

The Real Value of a Tender Comparison

A professional tender analysis does not simply tell a client which contractor submitted the lowest figure.

It answers more important questions:

Are all contractors pricing the same scope?

Are the material specifications consistent?

Are there significant omissions?

Are the rates realistic?

Are provisional sums comparable?

Are there unusual price differences that require clarification?

Only after these questions have been answered can a client make an informed decision.

Final Thoughts

When two contractors quote different prices for the same house, the difference is rarely explained by one simple factor.

It can come from quantities, specifications, provisional sums, exclusions, labour, overheads, construction methods and pricing assumptions.

This is why choosing a contractor based purely on the lowest quotation can be risky.

A properly prepared Bill of Quantities creates a common pricing basis, while professional tender analysis helps identify the differences hidden behind the final figures.

For a homeowner or developer, the goal should not simply be to find the cheapest quotation.

The goal should be to understand exactly what you are paying for.

Because in construction, two prices may look very different on paper, but until you understand what is behind those numbers, you may not actually be comparing the same project.