Ask an experienced construction manager what keeps them up at night and they will rarely say "the engineering." It is the contract. Who carries the risk of unforeseen ground conditions? What happens if the client changes the scope after mobilisation? Who is liable when a subcontractor default triggers a cascade of delays? These questions are all settled, well or badly, in the contract type chosen at the outset.
In Türkiye, where international investors increasingly work alongside local developers, contractors, and public entities, contract type selection carries an additional layer of complexity: different parties bring different assumptions about what a contract means and how disputes get resolved. A lump-sum turn-key arrangement that would function smoothly between two multinational contractors can become a source of protracted conflict when one party's default expectation is that everything is negotiable.
The main contract types in use
Turkish construction projects, both public and private, typically use one of four primary contract structures:
*Lump-sum:* The contractor delivers the defined scope for a fixed price. The client has cost certainty; the contractor carries the risk of underestimating. This works well when the design is complete and the scope is stable. It breaks down when changes are frequent or when subsurface conditions are uncertain.
*Unit price:* Payment is based on measured quantities at agreed unit rates. The client carries the volume risk; the contractor carries the rate risk. This is the dominant model for public infrastructure in Türkiye and is well understood by the local contractor market.
*Cost-plus:* The client pays actual costs plus an agreed fee. Maximum transparency for the client, minimum risk for the contractor. Rarely used in Türkiye outside of emergency works or highly complex, fast-track projects where scope cannot be defined in advance.
*Design-build:* The contractor takes responsibility for both design and construction. The client gets a single point of accountability. Used extensively in industrial and logistics development, less common in complex mixed-use projects where the client wants design control.
Why the choice is rarely straightforward
Each contract type performs differently depending on the specific combination of project characteristics. A lump-sum contract on a project with incomplete geotechnical data is not a fixed-cost project: it is a fixed-price argument waiting to happen. A unit price contract on a fast-track schedule creates a situation where the client is approving invoices before they have the bandwidth to verify quantities.
The decision is further complicated by the fact that different stakeholders weight the relevant criteria differently. A foreign equity investor prioritises cost predictability and exit clarity. A local developer prioritises speed to market and contractor relationships. A public-sector procuring entity prioritises regulatory compliance and audit trail. These preferences are not always compatible.
Applying Spherical AHP to contract selection
Analytic Hierarchy Process (AHP) is a structured method for multi-criteria decision making. It allows decision-makers to compare options against a set of weighted criteria, making the trade-offs explicit and the logic auditable. Spherical AHP is an extension that incorporates hesitancy: it acknowledges that experts are not always certain in their judgements and builds that uncertainty directly into the calculation.
In research applying Spherical AHP to Turkish construction contract selection, the key criteria identified by expert panels included: risk allocation appropriateness, cost certainty, schedule flexibility, design complexity, contractor market depth, and regulatory compliance burden. Each criterion was weighted according to project-specific conditions, and the four contract types were scored against each.
The findings confirmed several intuitions: lump-sum contracts are appropriate when design is complete and scope is stable; unit price contracts perform well for public infrastructure with measurable work items. But they also surfaced less obvious results. For complex mixed-use developments in Istanbul's urban transformation zones, design-build contracts consistently underperformed on the risk allocation criterion, not because the contract type is inherently flawed, but because the local contractor market at the required quality level is thin, concentrating risk in a small pool of capable firms.
Practical guidance for international investors
If you are entering the Turkish construction market for the first time, three principles apply regardless of which contract type you ultimately choose.
First, invest in the scope definition before you go to tender. The single largest driver of contract disputes in Türkiye is incomplete design documentation at the point of contractor engagement. A few extra weeks of design development at the front end will save months of claims management at the back.
Second, understand the local contractor market before you allocate risk. Türkiye has excellent Tier 1 contractors with strong international track records. But the depth of that tier in any given region or sector is limited. A lump-sum contract with a Tier 2 contractor on a complex project is not a fixed-cost solution: it is a fixed-price insolvency risk.
Third, build your dispute resolution mechanism carefully. Turkish courts are slow. International arbitration clauses are enforceable but add cost and complexity. For projects below a certain threshold, a well-structured adjudication mechanism with a Turkish-qualified neutral often produces faster and cheaper resolution than either domestic litigation or international arbitration.
Contract type is not a boilerplate decision. On Turkish construction projects, it is one of the three or four decisions that most determine whether a project delivers value or destroys it.