Ask an owner what the cost of design errors and omissions is likely to run on their project, and most reach for the same answer: a percentage they read somewhere, applied to the total budget, treated as fixed. That's a starting point, not an estimate. The real number depends on project type, how many disciplines are sharing a footprint, how far the design has actually matured, and — more than any of those — whether anyone has actually checked the set for the conflicts that drive that cost. A framework that accounts for all four gets an owner much closer to a real figure than a single borrowed percentage ever will.
What "cost of design errors and omissions" actually means
The phrase gets used loosely, so it's worth being precise about the category before estimating it. Design errors and omissions costs are the change orders, RFIs, and field rework that trace back to a mistake or a gap in the design documents themselves — a duct that was never checked against the structural beam it runs through, a spec section that contradicts the drawn detail it's supposed to describe, a note that assumes coordination the plans never actually show. That's a different category from owner-requested scope changes, which are a decision the owner made on purpose, and different from unforeseen site conditions, which no set of drawings could have shown in advance.
Industry research consistently separates these categories because they behave differently and respond to different fixes. A Construction Industry Institute study of nine large industrial construction projects found design error responsible for an average of 79% of total rework cost on those projects, with construction-phase deviations accounting for the remainder — and more recent industry cost-of-quality analyses put design errors and omissions at roughly a quarter to a third of total rework cost share, generally ranked as the largest or second-largest driver behind owner-requested changes. The consistent finding across studies, regardless of the exact split, is that design-stage mistakes are the biggest single lever an owner can pull before bid — because they're the one category still fixable as a redline instead of a change order.
Why a single percentage isn't an estimate
The 3%–5% of hard cost range we've cited before for design-related change order exposure — covered in more depth in change order math: calculating real exposure before you bid — is a real, defensible industry range. But it's a population average, built from a mix of project types, document maturities, and review practices. Applying it unadjusted to one specific project treats a data center MEP-heavy set and a single-story tenant improvement as carrying identical risk, which they don't.
A framework fixes that by starting from the same population range and then adjusting it against the specific project in front of you, instead of stopping at the borrowed number.
The FMI/PlanGrid industry study, based on nearly 600 construction professionals, put total U.S. construction rework cost at roughly $177.5 billion a year, with poor communication between project participants responsible for about 26% of it. That figure is an industry-wide average across every project type and review practice combined — exactly the kind of number a project-specific framework is meant to narrow down, not just repeat.
A four-step framework for estimating exposure
Step 1: Set the baseline from published ranges
Start with the population-level range for design-related cost exposure — roughly 3%–5% of hard construction cost, separate from the 10%–15%+ range that includes owner-requested scope changes and site conditions. Multiply that range against the project's hard cost to get an unadjusted floor and ceiling. This is the number most owners stop at. It's a real starting point, but it's not yet specific to the set in front of you.
Step 2: Adjust for project-specific risk factors
Three factors move a project up or down from the population baseline, and all three are knowable before bid:
- Discipline density. A project where structural, mechanical, electrical, plumbing, and fire protection are all sharing tight overhead space — a data center, a hospital, a lab building — carries more interface points than a project where two or three disciplines rarely touch the same physical zone. More interfaces means more places for a coordination conflict to hide.
- Design compression. A schedule that compressed design duration to hit an aggressive milestone, or a fast-tracked project issuing for construction before design is fully resolved, both correlate with a higher error rate, because fewer review cycles happened before the set went out.
- Team continuity. A design team assembled fresh for this project, with consultants who haven't worked together before, has more coordination risk than a team that has delivered similar projects together repeatedly, because shared conventions and expectations reduce the gaps that individual reviews miss.
A project scoring high on discipline density, design compression, or fresh team assembly should be estimated toward the top of the population range, or above it. A project low on all three can reasonably sit toward the bottom.
Step 3: Adjust for document review status
This is the step that actually changes the number, not just where in the range it sits. The population-level range describes projects across every level of document scrutiny — some reviewed rigorously across disciplines, most not. Whether a cross-discipline review has actually happened on this specific set is the single biggest lever on where the real exposure lands, because it's the only factor in this framework that measures whether the risk is still live or has already been checked.
That last row is the point of running a review at all: it doesn't just lower a percentage, it replaces the percentage with an actual list. A set that's passed single-discipline QA/QC hasn't moved off the top row, because QA/QC checks a discipline's drawings against that firm's own standards, not against every other discipline's sheets — the same gap covered in why "it passed QA/QC" doesn't mean the set is coordinated. BIM clash detection moves the needle further, but only for modeled geometry — it doesn't catch a spec section that contradicts a drawn detail or a written note that assumes coordination the plans don't show, a gap covered in catching design errors before construction: a practical checklist for owners.
Step 4: Convert the range into a decision
Once the range is adjusted for the specific project and its review status, the framework produces a decision an owner can actually act on: is the dollar range still sitting in this set large enough to justify the fixed, known cost of a document-level review that would convert it into a priced findings list instead? On a project where the adjusted range still runs into six or seven figures, a review costing a small fraction of that range — priced flat, not as a percentage of project value — is close to a formality. The framework's output isn't a number to file away; it's the input to that one decision.
Key takeaways
- The cost of design errors and omissions is a distinct category from owner-requested scope changes and site conditions — it's specifically the conflicts and gaps traceable to the design documents themselves.
- Industry research, including a Construction Industry Institute study of nine large industrial projects, consistently ranks design-stage mistakes as the largest or near-largest driver of total rework cost.
- A single population-level percentage isn't a project-specific estimate — it has to be adjusted for discipline density, design compression, and team continuity.
- Document review status is the biggest lever in the framework: it's the only factor that measures whether the exposure is still live or has already been checked and priced.
- The framework's purpose is a decision, not a number — whether the adjusted exposure still sitting in the set justifies a fixed-cost review before bid.
Frequently Asked Questions
What's the difference between "cost of design errors and omissions" and total change order costs?
Total change order costs on major projects commonly run 10%–15% of contract value, sometimes higher, and blend three categories together: owner-requested scope changes, unforeseen site conditions, and design errors and omissions. The design-error slice specifically — cross-discipline conflicts, spec-vs-drawing contradictions, and similar document-level mistakes — is the narrower category this framework estimates, generally in the 3%–5% range of hard cost before project-specific adjustment.
Can an owner estimate this cost without hiring a reviewer first?
The first three steps of the framework — baseline range, project-specific adjustment, and review-status adjustment — can be done with information the owner already has: hard cost, discipline count, schedule compression, and team history. What an owner can't estimate without a review is the fourth output: the actual, priced findings list a cross-discipline review would produce, which is the only way to convert a range into a specific dollar figure.
Does a higher project budget automatically mean higher design-error exposure?
Not proportionally beyond the baseline percentage range. A larger project has more absolute dollars at stake within the same 3%–5% range, but the multiplier itself is driven more by discipline density and design compression than by budget size alone — a smaller, MEP-dense healthcare renovation can carry a higher percentage-of-cost exposure than a larger, simpler warehouse shell.
Does BIM clash detection replace the need for this kind of exposure estimate?
No. Clash detection reduces the modeled-geometry portion of the exposure — physical overlaps a 3D model can catch — but doesn't touch spec-vs-drawing contradictions, written notes that assume unverified coordination, or missing detail callouts, all of which live in the documents rather than the model and still count toward the cost of design errors and omissions.