A common question among homeowners hiring contractors is: “If the contractor bids $300,000 to build my house and it ends up costing less, do I still pay the full $300,000?” The answer depends entirely on the type of contract you signed. This article explains the different contract structures used in residential construction, how savings (or overruns) are handled under each, and what you can do to protect your interests.
The Four Main Types of Construction Contracts
| Contract Type | How Pricing Works | Who Bears Cost Risk | Who Gets Savings |
|---|---|---|---|
| Fixed-Price (Lump Sum) | A single price for the entire scope of work | Contractor absorbs cost overruns | Contractor keeps savings (if any) |
| Cost-Plus (Time & Materials) | Actual costs + agreed markup (typically 10–20%) | Owner bears all costs | Owner receives savings |
| Cost-Plus with Guaranteed Maximum Price (GMP) | Cost-plus up to a cap; contractor absorbs overruns beyond GMP | Shared risk | Owner receives some or all savings (by negotiation) |
| Negotiated Bid | Custom terms negotiated between owner and builder | Variable | Variable |
How Fixed-Price (Lump Sum) Contracts Work
In a standard fixed-price competitive bid, the contractor estimates the cost of labor, materials, overhead, and profit, then submits a single price. If the actual cost to complete the work is lower than estimated, the contractor keeps the difference as additional profit. If the cost is higher, the contractor absorbs the loss (though change orders often push costs back to the owner).
Key point: In a fixed-price contract, you pay the agreed price regardless of the contractor’s actual costs. You do not get a refund if the job costs less than expected. This is the most common type of contract for residential construction.
How Cost-Plus Contracts Work
Under a cost-plus arrangement, the owner pays the actual cost of materials, labor, and subcontractors plus a contractor’s fee (usually 10–20% of costs or a fixed management fee). The contractor’s books are open to the owner for inspection. If costs come in under budget, the owner pays less. If costs overrun, the owner pays more.
Key point: With a cost-plus contract, if the job costs less than the initial estimate, you pay only the actual costs plus markup. You directly benefit from savings.
To ensure you have a solid understanding of the financial landscape, review cost estimation of construction projects before signing any contract.
Cost-Plus with Guaranteed Maximum Price (GMP)
A GMP contract combines elements of both approaches. The contractor sets an upper limit on the total cost. If actual costs are below the GMP, the savings may be shared between owner and contractor (e.g., 50/50) or returned entirely to the owner, depending on the agreement. If costs exceed the GMP, the contractor pays the overrun.
| Scenario | Fixed-Price $300K | Cost-Plus (15% markup) | GMP $300K (50/50 savings share) |
|---|---|---|---|
| Job actually costs $270K | Owner pays $300K (contractor keeps $30K) | Owner pays $310,500 ($270K + 15%) | Owner pays $285K ($270K + $15K shared savings) |
| Job actually costs $300K | Owner pays $300K | Owner pays $345,000 | Owner pays $300K (GMP caps it) |
| Job actually costs $330K | Owner pays $300K (unless change orders) | Owner pays $379,500 | Owner pays $300K (GMP caps at $300K) |
Why Jobs Rarely Come In Under Bid
In practice, construction projects almost always cost more than the original bid, not less. Understanding why can help you budget realistically:
Common Causes of Cost Overruns
- Changes in plans after work begins — Even small modifications trigger change orders that add cost.
- Inadequate allowances — Allowances for fixtures, flooring, cabinets, and appliances are often set too low. When you select premium options, you pay the difference.
- Hidden conditions — In remodeling especially, opening walls can reveal rot, outdated wiring, or structural issues that must be addressed.
- Unclear plans and specifications — Vague drawings lead to interpretation differences and change orders.
- Omissions in the bid — Items intentionally or unintentionally left out of the bid — such as permits, impact fees, landscaping, appliances, window treatments, and driveway paving — must be added later.
- Soft costs — Permit fees, impact fees, architectural fees, engineering reports, and inspection costs are often underestimated.
For an in-depth look at how to prepare a complete budget, learn how to estimate construction project costs comprehensively.
What Is a Deductive Change Order?
A deductive change order reduces the scope of work (and therefore the contract price). For example, if you decide to install laminate flooring instead of hardwood, the contractor issues a credit. However, deductive change orders are relatively rare in practice — most change orders are additive (increasing scope and cost).
To initiate a deductive change order:
- Request the change in writing.
- Obtain a written quote for the cost reduction.
- Ensure both parties sign the change order before proceeding.
How to Protect Yourself Regardless of Contract Type
- Define the scope completely before signing — the more detail in the plans and specifications, the fewer surprises.
- Include a detailed allowance schedule — list every finish item with realistic budget amounts.
- Require a line-item bid — even in a fixed-price contract, a detailed breakdown helps you compare bids and understand what is included.
- Build a contingency fund — set aside 10–20% of the total budget for unforeseen costs.
- Get multiple bids — three to five competitive bids help establish a realistic market price.
Understanding construction contracts in detail is essential before committing to any building project.
The Moral of the Story
The most important takeaway is to get your ducks in a row before signing a contract. Make sure the bid covers everything needed to complete the project to your satisfaction. The more complete and detailed your plans and specifications, the fewer opportunities for costly change orders. And if you want the opportunity to benefit from cost savings, negotiate a cost-plus or GMP contract rather than a fixed-price bid.
Learn more about understanding the bidding process to navigate contractor selection with confidence.
Real-World Examples of Cost Overruns vs. Underruns
Example 1: The Fixed-Price Surplus
A homeowner in Austin, Texas, signed a fixed-price contract for $320,000 to build a 2,200 sq. ft. home. The contractor estimated material costs based on lumber prices at the time of bidding. During construction, lumber prices dropped significantly. The contractor’s actual material costs were $18,000 below estimate. The homeowner paid the full $320,000, and the contractor pocketed the $18,000 as additional profit. The homeowner was satisfied because the house was completed on time and met specifications, but they had no claim to the savings.
Example 2: The Cost-Plus Windfall
A homeowner in Portland, Oregon, negotiated a cost-plus contract with a 12% builder fee for a 1,800 sq. ft. home. The initial estimate was $280,000. Through careful material selection, the homeowner sourced discounted cabinets and flooring, saving $15,000. The final cost was $265,000, and the homeowner paid $265,000 + 12% ($31,800) = $296,800 — significantly less than the $313,600 they would have paid if costs had matched the estimate. Under a fixed-price contract, they would have paid the agreed $280,000 regardless.
Example 3: The GMP Savings Share
A couple in Denver, Colorado, signed a GMP contract for $450,000 with a 50/50 savings split. The contractor completed the project for $420,000 — $30,000 under the GMP. The couple received a $15,000 refund at closing. The contractor kept $15,000 as a bonus for efficient management. Everyone was satisfied with the outcome.
Understanding Overhead and Profit in Bids
When comparing bids, it is helpful to understand how contractors structure their pricing. A typical breakdown looks like this:
| Component | Percentage of Total Bid | What It Covers |
|---|---|---|
| Direct Labor | 25–35% | Wages for carpenters, laborers, and trade subcontractors |
| Materials | 30–40% | Lumber, concrete, drywall, roofing, fixtures, finishes |
| Subcontractors | 15–25% | Electrical, plumbing, HVAC, insulation, drywall finishing |
| Overhead | 8–15% | Office rent, insurance, vehicles, tools, permits, bond premiums |
| Profit | 5–15% | Net profit margin for the general contractor |
| Contingency | 5–10% | Buffer for unforeseen conditions (applied to fixed-price bids) |
How to Negotiate a Savings-Share Clause
If you want to benefit from cost savings, consider negotiating a savings-share clause in your contract. Here are key terms to include:
- Definition of savings — clearly define what constitutes a cost savings (e.g., actual costs below the agreed budget or bid).
- Percentage split — common splits are 50/50 or 60/40 in favor of the owner.
- Audit rights — the owner must have the right to review all invoices, receipts, and subcontractor bills.
- Timing of payment — savings should be credited at closing or final payment, not as construction progresses.
- Exclusions — savings achieved through deductive change orders (scope reductions) should be treated separately from efficiency savings.
What to Look for When Comparing Bids
When you receive multiple bids, avoid simply choosing the lowest one. Instead, compare them line by line:
- Scope of work — does each bid include the same items? If not, create a checklist and ask bidders to confirm inclusion or exclusion.
- Allowances — are the allowances realistic? Lowball allowances are a common trick to make a bid look lower.
- Exclusions — what is explicitly excluded? Common exclusions include site work, landscaping, driveways, and appliances.
- Payment schedule — how much is due at signing, at each milestone, and at completion? Avoid contractors who demand more than 10% upfront.
- Warranty — what warranty is offered on workmanship (typically 1 year) and structural defects (typically 10 years in many states)?