Anyone who works in construction knows how unpredictable projects can be. From material price changes to unexpected delays, costs can spiral out of control. The best construction pros plan for uncertainty and strive to minimize risk.
Still, it would be great to have at least some level of certainty, especially when it comes to costs. This is where guaranteed maximum price (GMP) contracts come in.
As its name suggests, GMP guarantees a ceiling on what an owner will pay for a project. This type of contract caps project costs while still leaving room to be flexible.
In this guide, we'll explore how GMP contracts work, their pros and cons, and what contractors and clients should know before using one.
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A guaranteed maximum price, aka GMP contract, is a construction agreement that sets a maximum price the owner will pay, regardless of cost overruns. If expenses exceed this cap, the contractor may be responsible for covering the excess costs. If costs are lower than the maximum price, the savings may be divided between the contractor and the owner. It creates cost certainty for the owner while motivating contractors to manage budgets efficiently.
GMP agreements lend themselves well to large and complex projects because they bring a level of certainty with costs and can provide guardrails to unpredictable scopes.
This is particularly important in high-budget projects, as these carry greater financial risks. When there's a guaranteed maximum price, both owners and contractors can be on the same page with budget expectations from day one.
A properly executed GMP contract offers advantages for different project stakeholders. Consider the following:
A GMP contract outlines how the project will be run, the fees involved, as well as the terms and expectations for both parties. Here are the main elements you'll typically find:
| Contract Type | Key Features | Best For | Risk/Reward Distribution |
| GMP (Guaranteed Maximum Price) | Sets a cost ceiling; includes direct/indirect costs, contractor’s fee, and contingency allowance. Shared savings possible. | Large or complex projects needing cost certainty with some flexibility. | Risk is shared; owners gain cost protection, contractors benefit from efficiency and potential shared savings. |
| Cost-Plus | Reimburses actual costs plus contractor’s fee; no maximum limit unless capped with GMP. | Projects with evolving scope or incomplete design. | Owner carries most of the risk, contractor has guaranteed payment with less pressure to control costs. |
| Fixed-Price | Predetermined lump sum; contractor assumes most risk for overruns. | Smaller, straightforward projects with clearly defined scope. | Contractor carries the bulk of the risk but gains higher reward if costs are kept below the fixed price. |
Choosing the right contract type can make or break a project. Here's how GMP compares to other common construction agreements.
GMP contracts set a ceiling on costs, while cost-plus contracts reimburse actual expenses plus a contractor's fee, with no upper limit.
As such, GMP works best for larger, more complex projects where owners need cost predictability but also want flexibility. Teams can choose to use cost-plus when the scope is uncertain or the design is still evolving. For example, a new hospital wing with shifting requirements may suit cost-plus, while a mixed-use high-rise with financing tied to strict budgets fits a GMP contract.
Unlike GMP, where a maximum cap exists but costs can fluctuate within it, fixed-price contracts lock in a single amount from the start.
So while GMP is ideal for complex projects with potential unknowns, fixed-price contracts are better for straightforward builds with clearly defined scopes.
Developing and implementing a GMP contract requires careful planning and ongoing collaboration among owners, contractors, and project managers. Here's a look at what these agreements look like in practice.
The groundwork of a GMP contract is laid at the preconstruction stage. This is when project teams collaborate to define the scope of work, estimate costs, and identify potential risks.
Contractors provide detailed breakdowns of direct and indirect costs, along with allowances for contingencies. That way, owners gain visibility into how money will be spent.
The guaranteed price is what really defines the GMP contract. That's why one of the most critical steps in this process is establishing the threshold for total project costs. Some of the factors to consider include:
Once the project is underway, contractors are responsible for documenting and reporting costs against the GMP. For best results, contractors should keep owners in the loop to promote transparency. In the same vein, project managers should have visibility into project costs so they can spot potential overruns sooner rather than later.
No project goes exactly as planned, and that's where change order provisions come into play. In a GMP contract, adjustments to the scope may impact costs, but only with owner approval.
If changes push expenses higher, the GMP can be revised, but only after documenting the reasons and agreeing on a new ceiling.
This process ensures that owners stay in control of budgets while contractors are fairly compensated for additional work.
A GMP contract can create a healthier project environment for everyone involved. Consider the following.
With a cost ceiling in place, owners can move forward knowing they won't be hit with runaway expenses. This is especially important for projects tied to financing or strict budget limits. A GMP contract helps clients breathe easy, knowing that their maximum exposure is capped, even if unexpected issues arise.
Unlike rigid fixed-price contracts, GMP agreements allow contractors to adapt as projects evolve. If materials or designs change, contractors can adjust costs within the guaranteed ceiling. This flexibility enables them to manage risks more effectively while still delivering quality results.
GMP contracts require detailed cost breakdowns and ongoing reporting, which makes the process more transparent. Owners can see where their money is going, and contractors can demonstrate accountability at every stage. It keeps folks on the same page, paving the way for more transparency and trust.
GMP contracts can include shared savings clauses when projects come under budget. As such, contracts can reap the rewards of being cost-efficient, while owners enjoy reduced expenses. It's a win-win dynamic where both sides are motivated to control costs and avoid waste.
While GMP contracts offer plenty of benefits, they also come with trade-offs that owners and contractors need to navigate.
In some cases, disagreements can arise over what counts as a reimbursable expense. Owners may question charges for indirect costs or overhead, while contractors may feel they're not being paid fairly. This is why having clear definitions upfront is essential. Without having those expectations on paper, disputes can strain relationships and stall progress.
Contractors assume additional risk in GMP agreements. If costs approach the ceiling, they may face pressure to cut corners or push back on scope changes to avoid overruns. While this can drive efficiency, it also creates tension if not managed well.
The transparency of GMP comes at a cost: paperwork. These contracts require rigorous record-keeping, from cost reports to receipts, to prove expenses are legitimate. For contractors, that can mean dedicating significant time and resources to administration. For owners, it requires reviewing and understanding detailed reports.
To maximize the benefits of a GMP contract, teams must prioritize clarity, transparency, and collaboration throughout the entire process. Here are some best practices to keep in mind.
The foundation of a successful GMP project is a contract that leaves no room for ambiguity. That means your agreement must have clearly defined scope, roles, reimbursable costs, and exclusions in plain language.
When everyone understands what's covered—and what's not—you reduce the risk of disputes later. A well-written agreement also sets expectations around timelines, deliverables, and reporting, which helps keep projects moving smoothly and reduces stress for both owners and contractors.
Technology can make or break a GMP project. Modern construction management platforms simplify cost tracking, streamline documentation, and create real-time visibility into project performance.
Both owners and contractors benefit from having a single source of truth for budgets, schedules, and approvals. With the right software in place, teams spend less time chasing paperwork and more time focusing on quality execution.
Transparency only works if it's consistent. Providing owners with regular cost updates helps them stay confident that the project is under control. Open communication also makes it easier to discuss potential risks, scope changes, or savings opportunities before they escalate into problems.
Owners often want assurance that costs are accurate and fairly represented. Including audit rights in the contract ensures they can verify expenses. For contractors, adhering to clear documentation standards protects them from disputes and showcases accountability.
We've covered a lot of GMP fundamentals and best practices. Now, let's explore what these agreements could look like in action:
Let's say a developer is planning a new downtown office tower. Because lenders require strict cost control, the project team establishes a GMP cap to reassure investors and keep financing on track. The contract outlines direct and indirect costs, includes a contingency allowance, and sets a firm maximum budget. Even if material prices rise during construction, the developer knows the project won't exceed the agreed ceiling. For the contractor, the GMP provides flexibility to manage labor and resources efficiently while maintaining profitability.
Government-funded projects—like highways, schools, or transit hubs—often rely on GMP contracts. Taxpayer dollars demand accountability, so the contract includes a contingency buffer within the GMP to handle unforeseen issues, such as environmental conditions or regulatory changes. This approach creates transparency for the public while still allowing contractors to manage the complexities of large-scale infrastructure.
A university decides to renovate several campus buildings. To encourage cost efficiency, the GMP contract includes a shared savings clause. This means that if the project finishes under budget, both the university and the contractor share the savings. The arrangement motivates the contractor to find creative ways to cut waste and improve efficiency—whether through smarter material sourcing or streamlined labor scheduling. For the owner, it's a win-win: the project stays within budget, and savings are reinvested into future campus improvements.
GMP contracts provide the financial guardrails needed to move ambitious projects forward without constant fear of overruns. While they require more documentation, the benefits (especially when used in the right projects) can far outweigh the drawbacks. GMP contracts are particularly well-suited for projects where cost certainty, transparency, and flexibility are priorities. The success of such contracts relies on clear terms, detailed documentation, and strong relationships between all stakeholders.
