Before any construction starts, you and your builder agree on how you will be charged. The two most common structures are cost-plus and fixed-price, and the one you choose shapes your risk, your budget certainty, and your relationship with the contractor. Here is how they compare so you can pick the right one.
What is a fixed-price contract?
In a fixed-price (or lump-sum) contract, the builder gives you one total price for the entire project. You know the number up front, and the builder carries the risk if costs run over.
Pros:
- Budget certainty from day one
- The builder absorbs cost overruns
- Simple to understand and compare
Cons:
- Builders add a contingency buffer, so the price may be higher
- Less flexibility to change things mid-project
- Requires very detailed plans before pricing
What is a cost-plus contract?
In a cost-plus contract, you pay the actual cost of labor and materials plus an agreed fee for the builder, either a fixed amount or a percentage. Costs are transparent, but the final total is not fixed at the start.
Pros:
- Full transparency into real costs
- Flexibility to adjust as the project evolves
- No inflated contingency baked into the price
Cons:
- Less budget certainty up front
- Costs can climb if the project is not managed tightly
- Requires trust and clear reporting from the builder
Side by side
| Fixed-price | Cost-plus | |
|---|---|---|
| Budget certainty | High | Lower |
| Transparency | Lower | High |
| Flexibility | Lower | High |
| Who carries overrun risk | Builder | Owner |
| Best when | Plans are complete | Scope may evolve |
Which one protects you?
It depends on your project and your priorities:
- Choose fixed-price when the plans are complete and detailed, and you want maximum budget certainty. It is often best for well-defined projects like a specific remodel or an ADU from finished plans.
- Choose cost-plus when the scope may change, the project is complex, or you value transparency and flexibility, as long as you trust the builder and get clear cost reporting.
The role of the guaranteed maximum price
There is a middle path. A cost-plus contract with a guaranteed maximum price (GMP) gives you the transparency and flexibility of cost-plus, with a ceiling the total will not exceed. For many owners, this is the best of both worlds: open books plus a safety cap.
What matters more than the contract type
Any contract structure can work well or badly. What really protects you is a detailed scope, clear reporting, an honest builder, and a well-defined process for changes. The contract type sets the framework, but transparency and trust determine the outcome.
Frequently asked questions
Is cost-plus or fixed-price cheaper?
Cost-plus can be cheaper because it removes the contingency buffer builders add to fixed-price bids, but only if the project is managed tightly. Fixed-price gives more certainty for a potentially higher number.
What is a guaranteed maximum price?
It is a cap on a cost-plus contract. You get transparent, actual-cost billing, but the total is guaranteed not to exceed an agreed ceiling.
Not sure which structure fits your project?
JJP Construction works transparently and will walk you through the contract options for your specific job. Book a call and we will help you choose the structure that protects you best.
