Cost Plus Protection Checklist — BuildQuest

buildquest Cost Plus Checklist · Interactive

Construction Phase · Cost Plus Execution

Cost Plus Protection Checklist

Cost plus contracting works — when four pillars are in place. Without them, you’re rappelling without a rope. This checklist captures the sixteen moves that turn an open-book contract from a risk into a project you can actually manage. Work it before the first invoice. Bring it to your contractor meeting. Keep it visible through construction.

Quinn says

Cost plus isn’t dangerous because the contract is open-book. It’s dangerous when there’s no structure around it. Each item on this checklist is a piece of that structure. Don’t aim to finish the list in one sitting — aim to finish it before the first invoice. The contractor who’s right for cost plus will welcome every one of these. The one who pushes back is telling you something.

Live Dashboard

The Four Pillars of Cost Plus Protection

Each pillar holds up a different part of the contract. As you check items below, each pillar’s meter updates. A pillar turns green when complete.

Pillar 01

Billing discipline

0 / 5

Pillar 02

Documentation discipline

0 / 4

Pillar 03

Hybrid model moves

0 / 4

Pillar 04

Independent bill reviewer

0 / 3

Pillar 01 · Billing Discipline

Five things to settle before the first invoice

Billing frequency confirmed in writing

Weekly, biweekly, monthly — whatever cadence you and the contractor agree to. The point is that it’s written, not assumed. Surprise invoices kill cost plus relationships faster than anything else.
Loaded hourly rates documented for every trade

The rate billed to you must include wages, payroll taxes, workers comp, benefits, and any general conditions allocations. Get the loaded number per trade in writing — carpenter, laborer, foreman, project manager — so you’re not surprised when an invoice arrives.
Payroll honesty conversation completed

You’ve asked: are these the real loaded rates, or are they marked up? A contractor who can’t answer this clearly isn’t ready for cost plus. The one who answers honestly — even when the number is higher than you hoped — is the one to work with.
Contractor’s own time treated separately and explicitly

If the owner of the business is also on the job swinging a hammer, that time gets billed at a stated rate that’s separate from the company markup. No double-dipping — once through the markup, once through hourly billing. One or the other, never both.
Mistake handling agreed upon in advance

When a subcontractor measures wrong and has to redo work, who eats the cost — the contractor or you? Cost plus without this conversation defaults to billing the homeowner for every error. Settle the principle before there’s a real bill on the table.

The double-dipping trap. A contractor who marks up labor and also bills their own time as a separate line item is collecting twice for the same work. This is the single most common abuse in cost plus contracting. Read every invoice for it. Catch it once and it stops. Miss it for three months and it becomes the norm.

Pillar 02 · Documentation Discipline

On a cost plus job, the documentation is the protection

Receipt protocol established: every receipt identifies the project

If your contractor runs three jobs and brings a Home Depot receipt without a project name on it, you have no way to know whose materials you’re paying for. Receipts get a project ID written on them at the register or on the invoice header — every time, no exceptions.
WBS tagging in place for every line item

Work Breakdown Structure tagging means every charge — labor hour, material, subcontract — is coded to a category like Foundation, Framing, MEP rough, Drywall, Finishes. Without this, an invoice is one big number. With this, an invoice is a story you can read.
Seven-to-ten day invoice review window agreed

When an invoice arrives, you have seven to ten days to review it, ask questions, and approve or push back. The contractor agrees not to treat silence as approval — the clock is the clock, but the conversation must happen.
Backup documentation format defined and tested on invoice one

Each invoice arrives with receipts, time records, and subcontractor invoices attached. You and the contractor have agreed on the format — PDF bundle, shared folder, cloud accounting login — and you tested it on the first invoice so issues surface before the project is large.

A common ask, professionally handled

Asking for project identification on receipts isn’t an accusation. It’s a professional documentation standard. A contractor who reacts defensively to this request is telling you something about how they run their business. The contractor who’s been waiting for a homeowner to ask is the one you want.

Pillar 03 · Hybrid Model

Four moves that inch cost plus toward fixed price

Budget by WBS category — not one total number

A budget that reads “Foundation: $45K, Framing: $90K, Mechanical: $60K…” gives you a yardstick. A budget that reads “$750K total” gives you nothing. The category budget is the basis for monthly cost accounting against the WBS-tagged invoices.
NTE (Not To Exceed) clause negotiated and signed

An NTE cap turns cost plus into a hybrid: open-book mechanics with a ceiling. The contractor agrees that the total cost won’t exceed a number — and if it would, the conversation happens before, not after. The AIA A102 contract format is built for this.
Monthly cost accounting against the budget happening on schedule

Every month, side by side: what each WBS category was budgeted for, what’s been spent against it, what’s projected to complete. This is what the WBS tagging makes possible. Without the monthly review, the tagging is just paperwork.
Completion incentive structure agreed (50/50 or 70/30)

If the project comes in under the NTE cap, how do you and the contractor split the savings? A 50/50 split shares the upside fairly. A 70/30 in favor of the homeowner reflects the homeowner carrying most of the risk. Either works — what doesn’t work is leaving this unsaid.

A budget without an NTE is a wish list

A category budget tells you where the money should go. An NTE cap tells you where it stops. Without the cap, the budget is something the team consults — not something the contract enforces. The hybrid model only protects you when both pieces are in place.

Pillar 04 · Independent Bill Reviewer

Open-book transparency only works if someone is opening the book

Reviewer engaged: architect (CA services) or owner’s agent

Construction Administration services from your architect, or an independent owner’s agent — someone other than you, with construction expertise, reviewing every invoice. Typical fee: one to three percent of project cost, which on a $500K job is $5K–$15K. This is the cheapest insurance in residential construction.
Reviewer scope explicit in their contract

The reviewer’s contract spells out: review every invoice within the seven-to-ten day window, verify backup documentation, flag WBS variances against budget, raise mistake-charge questions, walk the site monthly to verify physical progress matches billed progress.
Three-way review rhythm established: contractor → reviewer → you

Invoice arrives to you and reviewer simultaneously. Reviewer flags items within five business days. You and reviewer caucus, then sit with the contractor. The rhythm is regular — not “let’s catch up sometime.”

The math on construction administration

A $5K–$15K CA fee on a $500K project is one to three percent of cost. If the reviewer catches a single $10K mistake-charge, a single $20K double-dipped labor item, or a single $30K runaway category — the fee paid for itself many times over. And on a project that comes in clean, you’ve bought peace of mind for the cost of a high-end appliance.

Status — start the checklist

Your protection status will appear here

As you check items above, this band tracks how many of the sixteen moves you’ve completed and which pillars are in place. The goal isn’t speed — it’s making sure each item is real before the first invoice arrives.

Quinn says

All four pillars in place doesn’t guarantee a perfect project — but it gives you the structure to handle whatever comes. Construction surprises happen. With the pillars, a surprise is a conversation. Without them, a surprise is a fight.

Two Stories

Same contract structure. Different outcomes.

Both projects ran on cost plus. The difference wasn’t the contract — it was whether the four pillars were standing up underneath it.

Ended well

The McMillans · $600K major remodel

Loaded labor rates documented before construction. Receipts tagged by WBS from invoice one. NTE cap of $625K. CA services from their architect at 2% of project cost.

When subs measured wrong twice and triggered redo work, the architect flagged the mistake-charge attempts and the conversation was professional, not adversarial.

Final result: 4% under the NTE cap. $10K back to the McMillans under the shared-savings provision.

Four pillars layered in

Ended badly

Ben & Jane · $200K primary suite

No loaded-rate documentation. Receipts came in batches without project tags. No NTE. No CA reviewer — Ben and Jane reviewed invoices themselves, when they had time, which was rarely.

Subcontractor errors got billed through. The contractor’s own time was billed hourly on top of labor markup. WBS categories ran 30, 40, 60 percent over with no early warning.

Final result: 40% over budget. Project finished, but the relationship didn’t survive it.

No pillars in place

Cost plus without structure is rappelling without a rope. The contract is fine. The rope is what makes the descent survivable. Sixteen items above. Don’t sign the first invoice without working them.

Quinn says

The right contractor for cost plus will recognize most of this list already. They’ve been waiting for a homeowner who shows up with structure instead of trust alone. Bring this checklist to your first construction meeting. The conversation it starts is the one that protects you for the next twelve months.

Enlighten, empower, protect. Now go make it happen.

— Bill Reid

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