How Often Do Construction Projects Go Over Budget? 2026 Data
Helonic is an AI construction drawing analysis platform for owners and contractors tracing construction cost overruns back to the drawing set. Construction projects go over budget about half the time, and the bigger the project, the worse the odds. This page collects the cost overrun statistics that get cited most (Flyvbjerg, KPMG, McKinsey, and a 125-project ASCE study), explains what each one measured, and uses Helonic's review of 1,000,000+ drawing pages to show which overrun drivers a team can still fix before bid.
What do the major cost overrun studies actually measure?
Each study below looked at a different population, so the numbers don't contradict each other. A megaproject database and a survey of owner executives answer different questions.
| Source | What it measured | Headline finding |
|---|---|---|
| Flyvbjerg and Gardner, How Big Things Get Done (2023) | 16,000+ large projects in 136 countries | 47.9% on budget; 8.5% on budget and on time; 0.5% on budget, on time, and on benefits |
| Flyvbjerg megaproject research | Projects of roughly $1 billion and up | About 9 in 10 had cost overruns |
| KPMG Global Construction Survey (2015) | Interviews with 109 senior owner executives | 31% of projects within 10% of budget; 25% within 10% of the original deadline |
| McKinsey Global Institute | Large capital projects | Typically 20% longer than scheduled and up to 80% over budget |
| ASCE study of design-build buildings | 125 design-build building projects | 21% overran cost; change-order count rose with project size |
Sources: Flyvbjerg and Gardner in Harvard Business Review, KPMG, Climbing the Curve, McKinsey, and the ASCE Journal of Legal Affairs and Dispute Resolution.
The most useful number for a building project is the gap between 47.9% and 8.5%. Hitting the budget is common enough; hitting the budget and the schedule together is rare. Teams that hold cost by stretching the schedule usually pay for it in general conditions later.
Why do larger projects overrun more often?
Larger projects have more interfaces between systems, and every interface is a place the documents can disagree. The ASCE design-build study found the number of change orders climbed with project size (a correlation of 0.59). Flyvbjerg's data shows the same pattern at the top end, where about 90% of megaprojects overrun against about 52% of the broader database.
Helonic sees it on the drawings. In the preconstruction risk findings from our review corpus, packages with nine major disciplines had about 1.7 times the issue density of packages with four or fewer. More disciplines means more sheets that have to agree with each other, and more chances for one of them not to.
How much of a cost overrun starts in the drawing set?
No study isolates one clean percentage, but the drawing set is the largest input a team controls. FMI's 2018 research for PlanGrid attributed 48% of U.S. rework to poor project data and miscommunication, about $31.3 billion that year. Our breakdown of construction rework costs walks through where that figure comes from.
Across Helonic's reviewed packages, the issues that turn into overruns cluster in a few categories:
- Cross-discipline coordination conflicts: about 34% of flagged issues. Roughly 8 in 10 packages had at least one.
- Missing or broken cross-references: about 21%. A callout to a detail that isn't in the set forces the bidder to guess.
- Specification-to-drawing mismatches: about 16%. Hardware, finishes, and equipment were the usual suspects.
- Code compliance gaps: about 13%, with fewer hits but a higher cost per fix because layouts move.
Each of those becomes an RFI during bidding or construction, and a share of the RFIs become change orders. The change order cost benchmark covers what that last step costs by project type.
Which overrun drivers can a team still control before bid?
Five drivers are still open when the set goes out for pricing:
- Estimate maturity. A schematic estimate carries a far wider accuracy range than a bid estimate. Our guide to how much contingency to carry maps those ranges by design stage.
- Set completeness. Missing sheets and schedules turn into allowances and exclusions. A drawing set completeness check finds them before the bid form does.
- Above-ceiling coordination. Architectural versus mechanical was about 29% of coordination conflicts in our data, mostly ceiling heights, diffusers, and access panels.
- Spec and drawing agreement. About 6 in 10 packages that included specs had at least one conflict between the drawings and the project manual. See spec-to-drawing conflicts.
- Late addenda. Packages with three or more addenda had about 35% higher issue density. That's a correlation, but it's a good flag for where to spend review time.
Owner scope changes, escalation, and differing site conditions sit outside this list. Clean documents make those cheaper to price, but they don't prevent them.
How does Helonic help keep a project inside its budget?
Helonic reads every sheet of a bid or IFC PDF set and flags the coordination conflicts, broken references, spec mismatches, and code gaps listed above, each with a sheet number and location. Estimators get a list of open risks to price or clarify, and the design team gets something specific to fix before addenda. Put a number on it for your own job with the rework savings estimator.
Practitioner insight
“When a job blows the budget, the post-mortem keeps landing on the same few sheets. It's the ceiling plan nobody checked against mechanical, or the door schedule that didn't match the hardware spec. We price what's drawn. If what's drawn is wrong, we're over before we mobilize.”
Source: Conversations with preconstruction directors and chief estimators at commercial general contractors, synthesized from Helonic's buyer-side interviews, Q2 to Q3 2026.
Construction Cost Overrun FAQ
What percentage of construction projects go over budget?
How far over budget do construction projects usually go?
Why do construction projects go over budget?
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Can drawing review prevent construction cost overruns?
Milind Sagaram
Co-founder & CEO, HelonicMilind is the co-founder and CEO of Helonic, where he leads product and go-to-market for AI-powered construction drawing analysis. He works closely with general contractors, project managers, estimators, and owners to understand how drawing quality drives project outcomes - and where AI can reduce RFIs, change orders, and rework. Milind has interviewed hundreds of construction professionals across project delivery roles, from preconstruction estimators at ENR top-400 contractors to facilities directors at institutional owners, and uses those conversations to shape both product direction and the way Helonic talks about the work.
- Construction project delivery and preconstruction
- RFI and change order economics
- Owner and GC workflows for drawing QA/QC
- Estimating risk and bid-stage scope assessment
How this page was researched: Third-party figures from Flyvbjerg and Gardner (2023), the KPMG Global Construction Survey (2015), McKinsey, and a 125-project design-build study in the ASCE Journal of Legal Affairs and Dispute Resolution in Engineering and Construction. Rework attribution from FMI's 2018 Construction Disconnected report. Issue categories, discipline pairs, and document-condition correlations from Helonic's review corpus (1,000,000+ pages, 2,000,000+ issues) through Q3 2026, reported as approximate shares.
Last reviewed by Milind Sagaram · September 27, 2026