Every construction contract is, underneath the paperwork, an answer to one question: when the job costs more than anyone expected, who pays for it? A lump-sum contract answers that the contractor does. A cost-plus contract answers that you do. Most of what tenants experience as a bad build-out, the budget that drifted, the invoice nobody could explain, the opening date that moved twice, traces back to signing the second kind of contract while assuming the protections of the first.
What a Lump-Sum Contract Actually Is
A lump-sum contract (also called fixed-price or stipulated-sum) commits the contractor to deliver a defined scope of work for a single stated price. You are not buying hours, materials, or the contractor's good intentions. You are buying a finished space at a number you can put in a budget and defend to a lender, a landlord, or a board. If the framing crew takes three days longer than the estimate assumed, that is the contractor's problem. If lumber moves against the buyout, that is also the contractor's problem. The price you signed is the price you pay.
That transfer of risk is the entire product. It is worth understanding precisely, because it is also the reason a lump-sum bid usually arrives higher than a cost-plus estimate for the same job. The contractor has priced the uncertainty and is carrying it. A cost-plus estimate looks cheaper on the page because the uncertainty has not been priced at all. It is still there. It is just sitting on your side of the table, and you will meet it later, one invoice at a time.
Where the Risk Sits in Each Model
| Contract type | Who absorbs an overrun | What you are really buying |
|---|---|---|
| Lump sum (fixed price) | The contractor, within the defined scope | A finished space at a committed number |
| Cost plus | The tenant, in full | The contractor's time and receipts, plus a fee |
| Cost plus with a GMP | Contractor above the cap, tenant below it | A ceiling, but not a price |
| Time and materials | The tenant, with no ceiling | Labor hours and invoices as they occur |
A guaranteed maximum price deserves a note, because it is often presented as the equivalent of a fixed price and is not. A GMP caps your exposure at the top, which is genuinely useful, but everything underneath the cap is still cost-reimbursable and still requires you to audit invoices. In practice, projects priced with a GMP tend to finish near the maximum rather than below it. The cap is real protection. It is not the same as knowing the number.
What Lump-Sum Pricing Protects You From
- Buyout risk: material price movement and subcontractor pricing between signing and installation are carried by the contractor, not passed through
- Productivity risk: crews that work slower than estimated cost the contractor margin, not you additional dollars
- Estimating error: a trade the contractor underpriced is a loss on their side of the ledger, and correcting it is not your invoice
- Invoice ambiguity: there are no labor hours or receipts to audit, because you are paying against completed milestones rather than costs incurred
- Budget defensibility: a single committed number is what a landlord's work letter, an SBA lender, or a franchisor approval package actually needs
What It Does Not Protect You From
This is the part most articles on the subject leave out, and leaving it out is how tenants end up feeling misled by a contract that worked exactly as written. A lump-sum price is fixed against a defined scope. Change the scope and the price changes with it. Three things legitimately move a fixed price, and you should expect all three to be possible on any build-out.
- Owner-directed changes: you upgrade the flooring, add an office, or move a wall after the drawings were priced. This is the most common cause of movement, and it is entirely within your control
- Concealed conditions: what is behind a wall or above a ceiling in a second-generation space cannot be priced from a site walk. Failed plumbing, undersized electrical service, or missing fire-rated assemblies surface after demo
- Authority-driven changes: a plan reviewer or inspector requires work the approved drawings did not show. Accessibility upgrades and fire-protection scope are the usual sources
A good lump-sum contract does not pretend these cannot happen. It states in advance how they get priced when they do: written change orders, a stated markup, your approval required before the work proceeds. That is the protection. Not the absence of change, but the absence of surprise about what change costs. We price and approve every change order before execution for exactly this reason, and a contractor who will not commit to that sequence in writing is telling you where they intend to make their margin.
What Has to Be True for a Lump Sum to Be Real
Written Scope
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A fixed price is only as solid as the scope it is fixed against, and a number can be called lump sum while carrying none of the protection. Before you treat a bid as a committed price, confirm all of the following, because each one is a place where a fixed price quietly turns back into an estimate.
| Confirm | Why it matters |
|---|---|
| The contractor walked the space | A price produced from drawings alone has not seen the existing conditions it is committing to |
| Drawings are permit-ready | Pricing schematic drawings means pricing assumptions, and assumptions resolve as change orders |
| Allowances are few and named | Every allowance is an open number inside a supposedly closed price |
| Exclusions are written down | Work the bid never mentions is work you will pay for separately |
| MEP scope is priced by the trades | Electrical, plumbing, and HVAC carried as a lump allowance is the single largest source of drift |
| Change-order terms are stated | Markup, approval sequence, and unit prices belong in the contract, not in a later conversation |
On our projects the licensed electrical, plumbing, and HVAC trades price their own scope under their own state licenses, and that pricing is carried inside the single contract you sign. Field labor runs through a vetted subcontractor bench under direct principal oversight. The reason that structure matters to a fixed price is accountability: the person who priced your job is the person running it in the field, so there is no gap between what was promised at the table and what gets built.
When Lump-Sum Is the Wrong Fit
Fixed pricing is not the right answer to every project, and pretending otherwise would cost you money. It is a poor fit in three situations. First, when the drawings genuinely are not ready and you need to start: a contractor forced to price incomplete documents will either load the number with contingency or fill it with allowances, and you get the worst of both models. Second, on heavy renovation of an old building where concealed conditions dominate the scope, the risk premium can exceed what the same work would cost reimbursable. Third, when you actively want to make selections as you go, a fixed price fights you, because every selection becomes a change order.
For most commercial tenant improvement work, none of those apply. You have a lease with a commencement date, a landlord work letter with a reimbursement mechanism, permit-ready drawings, and a business that needs to open. That is precisely the case a lump-sum contract is built for, and it is why we price every project that way.
How the Price Interacts With Your TI Allowance
One practical benefit is easy to miss. Most landlords reimburse a tenant improvement allowance against invoices, lien waivers, and evidence of completed work, and they reimburse up to a stated cap. A fixed contract price lets you calculate your out-of-pocket exposure on day one: contract price minus allowance equals your number. Under a cost-plus arrangement that figure stays unknown until closeout, which makes it very difficult to negotiate an allowance intelligently or to know whether the deal in front of you actually works.
Free Plan and Scope Review
Holding a proposal and not sure whether the price is genuinely fixed? We review drawings and competing scopes for DFW and East Texas tenants at no charge, and tell you plainly what is committed, what is an allowance, and what will come back later as a change order. Start at i30builders.com/commercial/plan-review/ or call (469) 721-0146.
Frequently Asked Questions
Common questions about this topic from DFW tenants, landlords, and business owners.
What is a lump-sum contract in commercial construction?
A contract committing the contractor to deliver a defined scope of work for one stated price. Cost overruns inside that scope are absorbed by the contractor rather than billed to the tenant, so the number you sign is the number you budget against.
Is a lump-sum contract more expensive than cost-plus?
The bid usually reads higher, because the contractor has priced the uncertainty and is carrying it. Under cost-plus that same uncertainty is unpriced and sits with you, surfacing later as invoices. Compare the finished cost of each model, not the starting number.
Can the price still change under a lump-sum contract?
Yes, in three legitimate cases: changes you direct, conditions concealed behind existing construction, and work required by a plan reviewer or inspector that the approved drawings did not show. Everything else is the contractor's risk, and every change should be priced and approved in writing before the work proceeds.
How is a GMP different from a fixed price?
A guaranteed maximum price caps your exposure but leaves the work cost-reimbursable underneath the cap, so you still audit invoices and still do not know the final number until closeout. Projects priced with a GMP commonly finish near the maximum rather than below it.
What makes a lump-sum bid unreliable?
Allowances covering scope the contractor could have confirmed by walking the space, MEP work carried as one lump figure rather than priced by the licensed trades, missing exclusions, pricing produced from schematic rather than permit-ready drawings, and change-order terms left out of the contract.
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