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Construction Contract Types Explained

The contract you choose decides who carries the risk of cost overruns, how you pay, and how much control you keep. Here are the main types used in India, and how to pick the right one.

AECORD Editorial3 min readConstruction 101

Lump-Sum (Fixed-Price) Contract

You agree one fixed price for a defined scope. The contractor carries the risk of their own cost overruns — if materials or labour cost more than they estimated, that is their problem, not yours. This gives you budget certainty, which is why it is popular with homeowners.

The catch: it only works if the scope and specification are clearly defined up front. Any change you make later ("actually, use imported tiles") becomes a variation and a price negotiation. Lump-sum also tempts a squeezed contractor to cut corners on unseen work, so it pairs best with clear specifications and good supervision.

Item-Rate (BOQ / Measurement) Contract

Instead of one price, you agree unit rates for each item of work — so much per cubic metre of concrete, per square metre of plaster, per kilogram of steel — set out in a Bill of Quantities (BOQ). You then pay for the quantities actually executed and measured.

This is fair when final quantities are uncertain, and it is the default for many larger and government works. It needs disciplined measurement (a measurement book) and can cost more than expected if quantities balloon, but you never pay for work not done. Common in the trade; heavier on paperwork for a homeowner.

Cost-Plus Contract

You reimburse the contractor's actual costs (materials, labour) plus an agreed fee — either a fixed amount or a percentage. It offers full transparency into where money goes and flexibility to change things as you build, which suits bespoke or evolving projects.

The weakness is obvious: with a percentage fee, the contractor earns more the more it costs, so there is little incentive to save. Use it only with a contractor you trust, ideally with a "guaranteed maximum price" cap, and expect to actively track spending.

Labour-Only and Turnkey

In a labour-only contract you supply all materials and pay the contractor (or thekedar) for labour alone — maximum control over material quality and cost, in exchange for doing all the procurement yourself. In a labour-plus-material contract the contractor supplies both.

At the other extreme, a turnkey (or design-build) contract hands one party responsibility for everything — design, materials, construction — and delivers you a finished building to "turn the key". It is the most convenient and the least hands-on, but you rely heavily on that single party, so their track record and a tight specification matter most.

Frequently asked

Which contract type is best for building a house?
For most homeowners with a well-defined design, a lump-sum (fixed-price) labour-plus-material contract gives the best mix of budget certainty and low day-to-day effort — provided the scope and specifications are pinned down first. If you want maximum control over materials and can supervise closely, labour-only works. Cost-plus suits bespoke projects with a trusted contractor. There is no universally "best" type; it depends on how defined your scope is and how hands-on you can be.
What is a BOQ and why does it matter?
A Bill of Quantities (BOQ) is an itemised list of every work item with its measured quantity and agreed unit rate. It underpins item-rate contracts, lets you compare contractors like-for-like, and forms the basis for valuing work and payments. Even on a lump-sum job, asking for a BOQ breakdown shows you what you are actually paying for.
Who bears the risk if costs go over budget?
It depends entirely on the contract type. In lump-sum, the contractor bears their own overrun risk. In item-rate, you pay for whatever quantities are executed, so higher quantities cost you more. In cost-plus, you reimburse actual costs, so you carry the overrun risk. Choosing the type is really choosing who holds this risk.

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