The MacLeamy Curve, Explained: Origin, Evidence, Criticism & the Cost of Late Change

The MacLeamy Curve is a conceptual model used in architecture, engineering and construction to explain an important project-delivery principle: a team's ability to influence cost and functional outcomes is generally greater earlier in a project, while the difficulty and potential consequence of change tend to increase as commitments accumulate.

The original diagram is more sophisticated than the familiar two crossing lines.

It also compares a traditional design-effort pattern with a preferred pattern that moves useful collaboration, information and design effort earlier.

The most important qualification is equally important:

The MacLeamy Curve is not a measured construction cost curve.

Its axes have no numerical units.

The original diagram does not establish a universal rule saying that a construction change costs 1x during design, 10x during documentation and 100x during construction.

It is best understood as a decision-timing and effort-distribution model, not a calculator.

For project teams trying to apply that principle rather than merely study the diagram:

• use the Floor Plan Review Checklist to examine the plan systematically;

• use Preconstruction Decision Review to identify the unresolved decision and next commitment;

• use the Construction Spatial Risk Score to screen where deeper spatial review may deserve attention;

• use the Construction Rework Exposure Calculator to model potential late-change financial exposure;

• use Full-Scale Spatial Validation if a physical 1:1 walkthrough is the appropriate review method; and

• use the Life-Size Floor Plan Cost Calculator only when the question is the cost of the physical print.

For students and teachers, this page can also function as a construction-management, architecture, engineering, BIM and CTE case study. The Big Floor Plans Education Hub, 75 Free Lesson Plans, Blueprint Reading Lesson, Construction & CTE Pathway, Lesson Plans by Standard, and Four Free Sample Plans provide classroom routes described later on this page.

What does the MacLeamy Curve actually say?

The familiar simplified MacLeamy diagram shows two crossing relationships over project time.

Curve 1 — Ability to impact cost and functional capabilities

The descending curve represents influence.

Early in a project, major aspects of:

• scope;

• configuration;

• layout;

• system selection;

• performance;

• user requirements; and

• function

may still be open.

As the project advances, some choices become constrained by:

• approvals;

• detailed documentation;

• permitting;

• contracts;

• procurement;

• fabrication;

• installation;

• completed construction.

The curve does not tell us that a team has exactly 80% influence during schematic design or 20% at construction start.

It describes a relationship, not a measured percentage.

Curve 2 — Cost of design changes

The rising curve represents the increasing potential consequence of changing something after related commitments have accumulated.

Early, a revision may primarily involve design and coordination effort.

Later, the same underlying decision may interact with:

• permitting;

• purchasing;

• supplier lead times;

• fabrication;

• mobilization;

• trade coordination;

• schedule logic;

• demolition;

• replacement of installed work.

Again, the original graph supplies no universal numerical scale.

Increasing consequence is the concept. The actual magnitude is project-specific.

The two MacLeamy curves most reproductions leave out

The original argument contains four curves, not two.

Curve 3 — Traditional design process

This curve represents a design-effort pattern whose peak occurs comparatively later, as construction documentation becomes more developed.

This makes the MacLeamy argument organizational as well as economic.

The question is not merely:

When does change become difficult?

It is also:

When is the project team doing the work needed to prevent important questions from surviving that long?

Curve 4 — Preferred design process

The fourth curve shifts the peak of design effort earlier.

In the original Construction Users Roundtable presentation, the terminology was “Preferred design process.”

The later AIA Integrated Project Delivery material associated the shifted curve with IPD.

That history matters because the original concept was broader than a single contractual delivery method.

The underlying proposition is:

move useful information, collaboration, stakeholder knowledge and interdisciplinary coordination forward so consequential decisions can be evaluated before downstream commitments reduce the available options.

Where did the MacLeamy Curve come from?

The most careful historical answer requires separating independently verifiable publication history from later first-person attribution.

The earliest independently verifiable publication Big Floor Plans has identified for the four-line diagram is the Construction Users Roundtable's 2004 white paper WP-1202, Collaboration, Integrated Information and the Project Life Cycle in Building Design, Construction and Operation.

CURT's publication archive continues to list WP-1202.
Construction Users Roundtable — WP-1202 publication archive

Patrick MacLeamy participated on the CURT committee as an HOK representative.

MacLeamy's own historical account says he developed the Effort Curve through that committee work and presented it at the 2005 AIA National Convention.

That is important first-person evidence, but it should be identified as MacLeamy's account rather than treated as independent proof of every historical detail.
Patrick MacLeamy — history of the Effort Curve

The American Institute of Architects' Integrated Project Delivery guidance subsequently used the diagram in explaining integrated project delivery and collaborative project processes.
American Institute of Architects — Integrated Project Delivery: A Guide

A careful chronology is therefore:

earlier construction influence concepts → CURT four-line diagram → MacLeamy attribution → AIA/IPD adoption → widespread BIM-era use.

Boyd Paulson documented the core construction idea in 1976

The influence-versus-commitment idea is older than the 2004 CURT figure.

In December 1976, Stanford researcher Boyd C. Paulson Jr. published Designing to Reduce Construction Costs in the ASCE Journal of the Construction Division.

Paulson described a construction relationship in which the ability to influence project costs declines as the project evolves, while actual expenditures increase.

He emphasized that the greatest leverage exists during engineering and design, when project expenditures are still comparatively small.
ASCE — Boyd Paulson, Designing to Reduce Construction Costs

Paulson's diagram is not the later four-line MacLeamy Curve.

It does not contain the traditional-versus-preferred design-effort pair.

A historically defensible interpretation is:

Paulson documented an earlier construction influence relationship. CURT later combined the influence/cost-of-change concept with an argument about redistributing design effort.

Paulson also described one often-repeated influence percentage as a rough but educated guess related to a particular project type.

It should not be transformed into a universal construction law.

The MacLeamy Curve is not a 1x–10x–100x construction law

One of the most common mistakes online is attaching precise phase-based multipliers to the curve.

You may encounter claims such as:

• 1x in design;

• 10x during documentation;

• 100x during construction.

Big Floor Plans has not identified a construction dataset that establishes those numbers as universal phase-by-phase multipliers.

The original CURT paper discussed ten-fold relationships from manufacturing context, but did not publish a construction dataset defining the numerical shape of the MacLeamy curves.

Software engineering has its own cost-of-change literature.

Aerospace and systems engineering have their own.

Those sources can be useful analogies.

They should not be relabeled as construction measurements.

Buildings are not software.

Construction projects are not aerospace systems.

An analogy is not a coefficient.

If a source shows a precise construction 1x–10x–100x ladder, ask:

What construction dataset produced those numbers?

Is the MacLeamy Curve based on measured data?

Not in its original form.

The original four-line diagram is best treated as a conceptual model.

That does not make it useless.

It means the evidence hierarchy should be kept clean.

Conceptual model

MacLeamy Curve
A schematic describing influence, change consequence and design-effort timing.

Empirical construction studies

Research using real project data to examine when effort occurs and how processes differ.

Rework and change-order evidence

Research describing actual project outcomes, error, field rework or change orders.

Systems-engineering precedents

Research and institutional guidance dealing with dependencies, iterations, maturity, decision gates and reversibility.

These bodies of evidence can inform one another.

They should not be collapsed into a claim that one dataset mathematically validates the original curve.

What real-project research found about time and effort

Lu et al. — BIM versus non-BIM project effort

Weisheng Lu, Ada Fung, Yi Peng, Cong Liang and Steve Rowlinson published Demystifying Construction Project Time–Effort Distribution Curves: BIM and Non-BIM Comparison in the ASCE Journal of Management in Engineering.

The authors noted that MacLeamy's curves were frequently cited while relatively little prior research had produced actual time-effort distributions from completed projects.

They analyzed two Hong Kong public-housing projects: one BIM project and one non-BIM project.

The observed curves showed more effort during architecture and engineering stages on the BIM project and a lower relative burden during the building stage.

That is directionally consistent with moving selected effort earlier.

It does not establish the universal shape, slope or timing of the MacLeamy Curve.
ASCE — Demystifying Construction Project Time–Effort Distribution Curves

The defensible conclusion is:

real project effort can be measured, and project process can alter when that effort occurs.

Technology alone does not move useful knowledge earlier

Ajibade Aibinu and Eleni Papadonikolaki studied effort distribution in a BIM-enabled design-and-build project.

Their research used quantitative project data, interviews with project actors and interviews with BIM experts.

A key finding was that lack of timely input from contractors, subcontractors and suppliers influenced inefficient effort-distribution patterns.

That adds important nuance to the MacLeamy discussion.

Moving a BIM model earlier is not enough if the people holding the relevant downstream knowledge still arrive late.
Construction Management and Economics — Aibinu & Papadonikolaki effort-distribution study

A better rule is:

move useful information and the people who hold it earlier—not merely software activity.

Change orders provide context, not coordinates for the curve

AIA Contract Documents has analyzed a large collection of construction contract data through its Construction Benchmark Database.

Its research on change orders was designed to investigate questions including:

• how many change orders projects receive;

• when change orders occur;

• cost variation;

• schedule variation;

• project differences.

That is valuable empirical construction evidence.
AIA Contract Documents — The Truth About Construction Change Orders

It is not a dataset assigning a specific dollar multiplier to each point on the MacLeamy Curve.

The proper interpretation is:

change orders are measurable project events whose consequence can interact with existing project commitments.

The improper interpretation is:

these percentages are coordinates on MacLeamy's conceptual diagram.

Modern field-rework evidence shows why definitions matter

A 2026 study by Peter E. D. Love, published in the ASCE Journal of Construction Engineering and Management, examined actual contractor field-rework records.

Average documented precompletion field rework in the studied data was approximately 0.38% of contract value.

When estimated postcompletion correction was considered, the study estimated an average around 0.76%.

The research also found substantial underreporting in the contractor's existing records.
ASCE — Quantifying the Costs of Field Rework in Construction

Those figures are considerably lower than many broad construction-rework claims.

That does not necessarily mean other studies are “wrong.”

They may be measuring different categories.

The ASCE study itself emphasizes that reported rework costs vary substantially because of different definitions and measurement methods.
ASCE explanation of the 2026 field-rework findings

The lesson for MacLeamy is important:

before attaching a percentage to “late change,” define exactly what the source counted.

Construction Industry Institute: rework can have a meaningful economic range

The Construction Industry Institute's A Guide to Construction Rework Reduction, IR252-2b states that rework on a typical project can cost approximately 2% to 20% of contract amount.

CII's work also emphasizes measurement, cause classification and corrective action as part of structured rework reduction.
Construction Industry Institute — A Guide to Construction Rework Reduction

That broad CII range and Love's narrow field-rework dataset should not be averaged together.

They illustrate why scope matters.

Big Floor Plans therefore keeps the MacLeamy Curve separate from the Construction Rework Exposure Calculator.

The MacLeamy page explains timing.

The Rework Exposure Calculator models financial exposure under disclosed assumptions.

Neither should pretend to be the other.

Avoidable error is broader than field rework

The UK's Get It Right Initiative reports international research placing measured direct avoidable construction-error cost around 5% of project value.

When indirect and unmeasured consequences are included, GIRI cites broader estimates ranging from approximately 10% to 25%.

GIRI also identifies root causes including:

• inadequate planning;

• late design changes;

• poorly communicated design information;

• poorly coordinated design information;

• poor interface management;

• ineffective communication.

Get It Right Initiative — Strategy for Change

These figures should not be described as measurements of the MacLeamy Curve.

They belong to a broader evidence layer about error and project processes.

Poor project information is a separate mechanism

The FMI / PlanGrid Construction Disconnected research found that survey respondents attributed:

• 26% of reported rework to poor communication; and

• 22% to poor project information.

The two categories totaled 48% of reported rework in the survey response.
FMI / PlanGrid — Construction Disconnected findings

This does not establish the shape of the MacLeamy Curve.

It illustrates one reason a decision may arrive late or fail.

Late problems can occur because:

• information was wrong;

• information was late;

• information existed but was inaccessible;

• information existed but was misunderstood;

• a decision was intentionally deferred;

• a requirement changed;

• a field condition contradicted an assumption;

• procurement created a new constraint;

• fabrication changed the available options;

• construction did not match the governing documents.

MacLeamy is a timing model, not a diagnosis of cause.

For a specific project, the Floor Plan Review Checklist and Preconstruction Decision Review are more appropriate tools for identifying what remains unresolved.

Time is not the only variable

A simplistic interpretation of the MacLeamy Curve makes elapsed project time appear to be the sole driver of change consequence.

Real projects are more complicated.

A better decision model considers at least four variables:

Decision type

What is actually being decided?

Dependency

How many systems, people, contracts or later decisions rely on it?

Reversibility

How difficult is the decision to change after commitment?

Timing

Which approvals, purchases, fabrication activities or installed work have already occurred?

A finish-color decision may remain reversible relatively late.

A structural grid, underground utility route, major equipment footprint or repeated prototype may create dependencies much earlier.

The key mechanism is often not simply:

time passed.

It is:

the project built a dependency network around the decision.

That is why the Preconstruction Decision Review asks about the next commitment rather than treating project phase alone as the answer.

Decision dependency is often the hidden driver

Imagine a room dimension.

At first, it may be a simple geometric decision.

Later, other systems may become coordinated around it:

• structure;

• plumbing;

• HVAC;

• electrical;

• equipment;

• accessibility;

• casework;

• millwork;

• furniture;

• finishes;

• procurement;

• user workflow.

The underlying dimension did not become expensive simply because a calendar moved forward.

It became harder to reverse because other decisions became dependent on it.

This is the stronger interpretation of the MacLeamy principle.

MIT systems thinking adds an important correction

MIT's systems-engineering and project-management materials provide a useful way to think about this problem without claiming that MIT validates the MacLeamy Curve.

Design Structure Matrix: map dependencies

MIT OpenCourseWare's System Project Management course includes the Design Structure Matrix, sequencing, managing iterations, project dynamics and the rework cycle.
MIT OpenCourseWare — System Project Management

The DSM method is valuable because complex decisions often depend on information produced elsewhere in the project.

A decision cannot simply be “moved left” if the information required to make it responsibly still arrives from the right.

MIT's course includes dedicated material on Design Structure Matrices and managing iteration.
MIT OpenCourseWare — Design Structure Matrix lecture

A better target is:

move the dependency information earlier where practical—not merely the deadline.

Early learning is not the same thing as early lock-in

MIT OpenCourseWare's Systems Engineering materials include topics such as:

• Lean Thinking;

• Set-Based Design;

• Decision-Based Design;

• Pugh concept selection;

• Controlled Convergence.

MIT OpenCourseWare — Systems Engineering lecture sequence

These ideas provide a useful counterweight to a simplistic MacLeamy interpretation.

The goal should not be:

pick one solution as quickly as possible.

The goal is:

increase useful learning early enough that irreversible choices can be made with better information.

MacLeamy versus the “last responsible moment”

Lean Set-Based Design intentionally keeps multiple feasible options alive while information improves.

The Lean Construction Institute describes teams developing options in parallel and postponing final commitment until the last responsible moment—the point at which keeping the decision open longer would begin to harm the project.
Lean Construction Institute — Set-Based Design

At first this may sound opposite to MacLeamy.

It is not.

A useful synthesis is:

Learn as early as possible.

Commit as late as responsibly possible.

Early learning is good.

Premature commitment is not.

The last responsible moment is also not procrastination.

It is the latest point at which a decision can remain open without materially damaging downstream coordination, procurement, schedule or other commitments.

Iteration is not the same thing as rework

Complex design requires iteration.

That is not automatically a failure.

A useful distinction is:

Productive iteration

Deliberate exploration that generates information while important options are still open.

Negative rework

Repeating, undoing or replacing work because a missing requirement, failed coordination, misunderstood decision or invalid assumption surfaced after dependent work advanced.

The goal is not zero iteration.

The goal is to move intentional learning before expensive commitment and reduce avoidable repetition afterward.

Information maturity is not the same as design maturity

A project can look highly developed while still relying on weak information.

A polished model may still contain unresolved assumptions.

Conversely, an early design can be supported by strong information about:

• site conditions;

• stakeholder requirements;

• operational needs;

• equipment;

• budget;

• regulations;

• interfaces;

• project constraints.

Before forcing a decision earlier, ask two questions:

How mature is the proposed solution?

How mature is the information required to judge that solution?

Moving a decision earlier is productive only if the project can also move enough of the required information earlier.

NASA provides a useful decision-gate analogy

NASA does not validate the MacLeamy Curve or Big Floor Plans.

Its systems-engineering practices are useful because they make decision readiness explicit.

NASA describes major project phases as separated by Key Decision Points, where decision authorities evaluate readiness to progress.
NASA Systems Engineering Handbook — program/project life cycle and Key Decision Points

The relevant principle is:

progress should depend on evidence of readiness, not merely passage of time.

NASA technical reviews use readiness criteria

NASA's current Systems Engineering Processes and Requirements include defined entrance and success criteria for major technical reviews.

For example, NASA's Preliminary Design Review evaluates whether preliminary design meets system requirements with acceptable risk and provides a basis for proceeding into detailed design.
NASA NPR 7123.1D — Life-Cycle and Technical Review Entrance and Success Criteria

That produces a stronger construction analogy than:

“schematic design is over, therefore the decision must be final.”

A useful project gate instead asks:

• Is the decision sufficiently defined?

• Are the inputs mature enough?

• Are important stakeholders represented?

• Are major risks understood?

• Are relevant interfaces known?

• Is the project actually ready for the next commitment?

Early is not enough. Ready is the standard.

NASA also demonstrates progressive review fidelity

NASA's Habitability Design program describes a human-centered process that matures concepts through:

concept sketches → CAD → scaled prototypes → virtual reality → full-size mockups

NASA says the iterative process allows stakeholders to provide early feedback and supports usability assessment.
NASA — Habitability Design and full-size mockups

That sequence provides a useful representation principle for building projects:

do not automatically start with the highest-cost or highest-fidelity review method.

Increase fidelity when the unresolved question requires information the current representation cannot provide.

A drawing may be enough.

A BIM model may be enough.

A field verification may be required.

A VR environment may be useful.

A constructed mockup may be justified.

Some horizontal spatial decisions may benefit from a portable physical 1:1 life-size floor plan.

The MacLeamy Curve itself does not choose the method.

The Preconstruction Decision Review is the BFP tool designed for that decision.

Front-end planning provides stronger empirical support than the literal curve

The most defensible evidence for the practical direction behind MacLeamy may come from front-end planning research, rather than attempts to prove the literal geometry of the drawing.

The Construction Industry Institute's Data Analysis in Support of Front End Planning Implementation analyzed more than 600 projects representing almost $37 billion in total installed cost.

The work compared front-end-planning measures including:

• PDRI;

• pre-project planning;

• percent design complete;

• alignment

with project performance measures including:

• cost;

• schedule;

• change orders.

Construction Industry Institute — Data Analysis in Support of Front End Planning Implementation

That is substantially stronger empirical evidence for the value of structured early planning than simply pointing to the shape of the MacLeamy drawing.

CII also explicitly describes front-end planning as an activity that requires real upfront effort, rather than pretending earlier planning is free.
Construction Industry Institute — Front End Planning guidance

The correct conclusion is:

selected information, coordination, scope definition and decision work can productively move earlier.

The incorrect conclusion is:

a measured universal MacLeamy curve has been scientifically validated.

What the MacLeamy Curve does not tell you

It does not tell you to freeze everything early

Some decisions should remain open while alternatives are studied and information improves.

It does not tell you that more early meetings are automatically valuable

Moving waste earlier does not create value.

Early effort needs to reduce meaningful uncertainty.

It does not tell you who pays for early effort

An architect, engineer or contractor may perform more work earlier while the owner captures much of the downstream benefit.

Fee structures and procurement matter.

It does not select the review medium

The diagram cannot tell you whether a decision requires:

• a drawing;

• BIM;

• VDC;

• VR;

• AR;

• physical mockup;

• field verification;

• survey;

• life-size printed plan.

It does not predict your project's change cost

The axes have no numerical units.

It does not establish a universal ROI

The graph is not financial proof for any vendor, product or review method.

A better interpretation: move learning left, not blind commitment

After examining the history, evidence and criticisms, a stronger practical interpretation of the MacLeamy principle is:

• Identify consequential unresolved decisions early.

• Identify the information those decisions depend on.

• Identify the people who hold that information.

• Bring useful dependency information forward where practical.

• Use the lightest credible representation that can answer the question.

• Keep alternatives open when important uncertainty remains.

• Commit when the evidence is sufficient and before downstream dependencies make reversal disproportionately difficult.

• Record the decision in the governing project information.

• Revalidate when later changes invalidate earlier assumptions.

That is more useful than:

“Make every decision early.”

How Big Floor Plans applies the MacLeamy principle

Big Floor Plans does not use the MacLeamy Curve as proof that every project needs a life-size floor plan.

Instead, the principle helps organize a broader preconstruction decision system.

Floor Plan Review Checklist

Use this when the first question is:

What should we actually review in the floor plan before building?

The checklist helps organize review of rooms, circulation, furniture, equipment, site relationships, rough-ins and other plan decisions.

Preconstruction Decision Review

Use this when the question is:

What is unresolved and what is the lightest credible way to check it before the next commitment?

This is the route-selection tool.

A printed floor plan is one possible result, not the default.

Construction Spatial Risk Score

Use this when the question is:

Where does this project concentrate characteristics that may deserve deeper spatial review?

It is a screening model, not a defect prediction.

Construction Rework Exposure Calculator

Use this when the question is:

How large might spatially addressable late-change exposure be under disclosed assumptions?

It models exposure.

It does not predict savings.

Full-Scale Spatial Validation

Use this when the project team has determined that a physical 1:1 review is appropriate.

The methodology connects:

current drawings → physical review → observations → decisions → revised governing information

Life-Size Floor Plans

Use this page when the question is:

What is a printed 1:1 floor plan, how does it work and what are its limitations?

Life-Size Floor Plan Cost Calculator

Use this only when the question is:

What does the selected printed area cost?

Keeping these questions separate prevents a conceptual model from being turned into a sales conclusion it does not support.

How the MacLeamy Curve applies to life-size floor plan review

A physical 1:1 floor plan can be useful when a project contains spatial questions that stakeholders can evaluate more effectively at body scale.

Examples can include:

• room proportions;

• furniture;

• circulation;

• door relationships;

• kitchens;

• bathrooms;

• equipment;

• maintenance access;

• patient or staff workflow;

• industrial layouts;

• data-center service zones;

• pre-slab relationships.

The strongest timing is generally:

after enough information exists to make the review meaningful, but before the relevant construction, procurement, fabrication or installation commitment makes the decision difficult to reverse.

That is the MacLeamy principle applied carefully.

It is not:

print everything as early as possible.

MacLeamy Curve for Students & Teachers

The MacLeamy Curve can also be a strong teaching tool because it connects construction, engineering, economics, project management, systems thinking, evidence literacy and design in one diagram.

Students do not have to purchase a Big Floor Plans print to use it.

The page can support classroom discussion from middle-school design activities through high-school CTE and introductory college architecture, engineering or construction-management instruction.

What can students learn from the MacLeamy Curve?

Construction project sequencing

Students can investigate why decisions made during:

• planning;

• design;

• documentation;

• procurement;

• construction

do not have the same consequences.

Blueprint reading

A construction drawing represents decisions.

Students can identify which information is fixed, which remains open and what other documents may control the answer.

Continue to the Blueprint Reading Lesson Plan for CTE, which teaches students to distinguish dimensions, symbols, references and governing information.
Big Floor Plans — Blueprint Reading Lesson Plan for CTE

Construction math and estimating

A design change can alter quantities.

Students can explore how changes to:

• room size;

• wall length;

• flooring;

• drywall;

• cabinetry;

• material quantities

flow into estimating exercises.

The Construction & CTE Pathway moves students through blueprint reading, scale, quantity takeoff, estimating and volume reasoning.
Big Floor Plans — Construction & CTE Pathway

Engineering design

Students can compare alternatives, constraints, trade-offs and the timing of decisions.

The important lesson is not simply:

choose early.

It is:

gather information, test alternatives and understand what becomes difficult to reverse.

Systems thinking

Students can map how one decision affects another.

A simple floor-plan dimension might connect to:

wall → door → furniture → electrical → plumbing → equipment → quantity → cost

That is an accessible introduction to dependency thinking.

Evidence literacy

The MacLeamy Curve is especially useful for teaching the difference between:

• a conceptual model;

• an empirical dataset;

• an analogy;

• a case study;

• a vendor claim;

• a peer-reviewed study.

Students can ask:

What does this source actually prove?

That question is valuable far beyond construction.

A classroom MacLeamy Curve activity

A teacher can turn this page into a short project-management exercise.

Step 1 — Choose a plan

Use:

• an authorized school or construction drawing;

• a teacher-created plan;

• a student-created plan; or

• one of the Four Free Big Floor Plans Sample Plans.

The four BFP sample plans are available without registration and are published for educational use.
Big Floor Plans — Four Free Sample Plans

Step 2 — Identify five decisions

Examples:

• room dimensions;

• door location;

• equipment location;

• plumbing fixture;

• wall configuration.

Step 3 — Map dependencies

For each decision, ask:

What else depends on this?

Step 4 — Rank reversibility

Ask:

When is this easy to change?

What commitment would make it harder?

Step 5 — Choose a review method

Would the decision be best evaluated through:

• the drawing;

• calculation;

• BIM;

• a physical measurement;

• a temporary tape layout;

• VR;

• a full-scale mockup?

Step 6 — Defend the timing

Students explain when they would commit the decision and why.

This turns the MacLeamy Curve from a diagram to an applied exercise in:

information → dependency → review → decision → commitment

Connect the MacLeamy Curve to 75 free lesson plans

Big Floor Plans currently publishes 75 free classroom-ready lesson plans spanning mathematics, STEM, construction trades, blueprint reading, design and related subjects.

Teachers do not have to buy a Big Floor Plans print to use the library.

Activities can use:

• a classroom drawing;

• student-created plans;

• the four free BFP Sample Plans;

• measured existing spaces;

• temporary tape or chalk layouts.

Big Floor Plans — 75 Free Lesson Plans

The strongest education path from this page is:

MacLeamy Curve → Sample Plan → Blueprint Reading → Scale → Construction Math → Estimating → Engineering Decision-Making

Teachers can route by standards and frameworks

The Big Floor Plans Standards Finder currently connects the lesson library to 100 mapped standards and framework references.

These include a mixture of:

• exact standards;

• broader domains;

• CTE frameworks;

• accreditation references;

• accessibility references;

• instructional planning categories.

The mappings are BFP-created educational crosswalks, not official approvals by the organizations that publish the underlying standards.
Big Floor Plans — Lesson Plans by Standard

For classroom use, the MacLeamy Curve is particularly relevant to topics involving:

• engineering design;

• construction;

• CTE;

• architecture;

• project management;

• systems thinking;

• optimization;

• trade-offs;

• evidence evaluation.

Education should teach the distinction between model and evidence

This page provides an unusually useful example.

Students can compare:

Concept

MacLeamy Curve

Historical source

CURT

Earlier precedent

Paulson

Empirical construction study

Lu et al.

Project-management research

CII front-end planning

Large construction dataset

AIA change-order research

Systems thinking

MIT DSM and set-based design

Institutional decision gates

NASA systems engineering

Then ask:

Which source supports which claim?

That is exactly the kind of source discipline used throughout the Big Floor Plans Education system.
Big Floor Plans — STEM, CTE & Architecture Education Hub

What most MacLeamy Curve pages get wrong

A reliable treatment should preserve these distinctions:

The original diagram has four curves, not two.

The vertical axis is conceptual rather than a measured dollar scale.

The original CURT terminology used “Preferred design process.”

The influence-versus-commitment principle predates the 2004 CURT diagram.

Boyd Paulson documented a related construction relationship in 1976.

The common 1x–10x–100x rule is not a universal construction result generated by MacLeamy's graph.

Later BIM research can test effort distribution without proving the literal curve.

Rework data provide economic context, not MacLeamy coordinates.

Moving work earlier is useful only when the necessary information and stakeholders move with it.

Early learning should not be confused with premature design freeze.

Frequently asked questions about the MacLeamy Curve

What is the MacLeamy Curve?

The MacLeamy Curve is a conceptual AEC diagram illustrating the relationship between project timing, ability to influence outcomes, potential consequence of design change and the timing of design effort.

Who created the MacLeamy Curve?

Patrick MacLeamy became associated with the curve and says he developed the Effort Curve through Construction Users Roundtable committee work.

The earliest independently verifiable BFP source for the four-line diagram is CURT WP-1202 from 2004.

Is the MacLeamy Curve scientifically proven?

Not as a universal measured curve.

Its original axes do not contain empirical numerical units.

Later studies have tested related ideas such as project effort distribution, BIM process timing, front-end planning, rework and change-order behavior.

Does the MacLeamy Curve prove that changes cost 10x or 100x later?

No.

Big Floor Plans has not identified a construction dataset establishing a universal 1x–10x–100x phase multiplier from the MacLeamy Curve.

Does the MacLeamy Curve prove BIM saves money?

No.

It has frequently been used to explain the rationale for earlier BIM-enabled coordination.

Actual BIM value depends on implementation, project conditions, team structure, information timing and use case.

Is MacLeamy saying every decision should be made early?

No.

That interpretation is too simplistic.

A better principle is:

move learning and useful information earlier; preserve valuable options where uncertainty remains; commit before delay begins to damage downstream work.

What is the relationship between MacLeamy and the last responsible moment?

They are compatible when interpreted carefully.

MacLeamy supports earlier learning and coordination.

Set-based design supports keeping viable alternatives open until further delay would harm the project.

Together:

learn early, commit responsibly.

What is the relationship between the MacLeamy Curve and construction rework?

The curve provides a conceptual explanation for why a late decision may interact with more existing commitments.

Rework studies independently measure actual corrective work or broader error categories.

Rework statistics should not be placed directly on the MacLeamy graph as though they generated its curves.

What is the relationship between the MacLeamy Curve and change orders?

Change orders are actual project events.

They can occur for many reasons, including legitimate scope changes.

AIA change-order data can provide real construction context, but it does not numerically validate the MacLeamy Curve.

What is the relationship between MacLeamy and front-end planning?

Front-end-planning research provides stronger empirical support for investing in selected early definition, alignment and coordination than the conceptual curve alone.

CII has analyzed more than 600 projects representing almost $37 billion in installed cost in its front-end-planning research.

How does the MacLeamy Curve apply to architects?

It can help explain why bringing owners, users, consultants, contractors and other relevant stakeholders into important design discussions before downstream commitments may preserve more options.

How does the MacLeamy Curve apply to builders?

It provides a framework for asking which unresolved decisions should be reviewed before procurement, slab work, rough-ins, framing, fabrication or installation reduce reversibility.

How does the MacLeamy Curve apply to students?

Students can use the curve to learn construction sequencing, project management, design dependencies, trade-offs, blueprint reading, cost thinking and the difference between conceptual models and empirical evidence.

Can teachers use the MacLeamy Curve in a construction or STEM lesson?

Yes.

Teachers can combine this page with BFP's free Sample Plans, Blueprint Reading lesson, Construction & CTE Pathway, 75 Free Lesson Plans and Standards Finder.

A purchased life-size print is not required.

Does NASA validate the MacLeamy Curve?

No.

NASA is cited because its systems-engineering processes provide useful independent examples of stakeholder involvement, progressive fidelity, decision maturity and evidence-based review gates.

Does MIT validate the MacLeamy Curve?

No.

MIT educational sources are relevant because they teach systems-engineering concepts such as dependencies, iteration, set-based design and controlled convergence.

They are not endorsements of Big Floor Plans or proof of MacLeamy's literal curve.

Primary MacLeamy Curve and decision-timing sources

Construction Users Roundtable — WP-1202

Collaboration, Integrated Information and the Project Life Cycle in Building Design, Construction and Operation

The earliest independently verifiable publication Big Floor Plans has located containing the four-line diagram.

View the CURT publication archive

Patrick MacLeamy

MacLeamy's own historical account says he developed the Effort Curve through CURT committee work and presented it at the 2005 AIA National Convention.

Read Patrick MacLeamy's account

American Institute of Architects

Integrated Project Delivery: A Guide

AIA's IPD guidance helped institutionalize the MacLeamy Curve in discussions about collaborative project delivery.

View AIA Integrated Project Delivery guidance

Boyd C. Paulson Jr. — ASCE, 1976

Designing to Reduce Construction Costs

Earlier construction research describing the decline in ability to influence project costs as a project progresses.

View the ASCE study

Lu et al. — ASCE, 2015

Demystifying Construction Project Time–Effort Distribution Curves: BIM and Non-BIM Comparison

Empirical comparison of time-effort distributions for two real public-housing projects.

View the ASCE study

Aibinu & Papadonikolaki

Conceptualizing and operationalizing team task interdependences: BIM implementation assessment using effort distribution analytics

Evidence that stakeholder timing and task interdependence can affect effort distribution in a BIM-enabled project.

View the Construction Management and Economics study

Construction Industry Institute

Data Analysis in Support of Front End Planning Implementation

More than 600 projects representing almost $37 billion in total installed cost were included in the analysis.

View CII's front-end-planning research

Construction Industry Institute

A Guide to Construction Rework Reduction

CII's rework-reduction guidance and broad 2%–20% contract-amount context.

View CII IR252-2b

Peter E. D. Love — ASCE, 2026

Quantifying the Costs of Field Rework in Construction

Actual contractor field-rework data providing an important counterpoint to broader rework estimates.

View the ASCE study

AIA Contract Documents

The Truth About Construction Change Orders

Large construction-data analysis providing context about real change-order behavior.

View the AIA research

FMI / PlanGrid

Construction Disconnected

Industry survey evidence regarding communication, project information and reported rework.

View the FMI / PlanGrid findings

Get It Right Initiative

Research into avoidable construction error, root causes and broader direct/indirect costs.

View GIRI's Strategy for Change

MIT OpenCourseWare

System Project Management and Systems Engineering

Independent education resources on DSM, dependencies, iteration, set-based design and controlled convergence.

View MIT System Project Management

View MIT Systems Engineering

NASA Systems Engineering

Independent institutional examples of Key Decision Points, technical-review maturity criteria, stakeholder involvement and progressive representation fidelity.

NASA Systems Engineering Handbook

NASA Habitability Design — concept to full-size mockup

Continue from theory to project action

Need to understand what is still unresolved in the plan?
Use the Floor Plan Review Checklist.

Need to determine the next credible check?
Use Preconstruction Decision Review.

Need to screen spatial uncertainty?
Use the Construction Spatial Risk Score.

Need to model the economic scale of late spatial change?
Use the Construction Rework Exposure Calculator.

Need to understand physical 1:1 review?
Use Full-Scale Spatial Validation.

Need to understand the physical format itself?
Read Life-Size Floor Plans.

Need preliminary print pricing?
Use the Life-Size Floor Plan Cost Calculator.

Need the broader independent evidence base?
Use the Construction Research & Source Library.

Teaching this concept?
Start with the Big Floor Plans Education Hub, then use the 75 Free Lesson Plans, Four Free Sample Plans, Blueprint Reading Lesson, Construction & CTE Pathway, or Lesson Plans by Standard.

The most useful takeaway from the MacLeamy Curve is not:

“Make every decision early.”

It is:

Move useful learning, information and stakeholder knowledge earlier. Understand dependencies. Preserve valuable options while uncertainty remains. Then resolve consequential decisions before the next commitment makes them materially harder to reverse.

Published by Big Floor Plans. Last substantive evidence review: September 2026.

Big Floor Plans has a commercial interest in earlier spatial review because it produces printed 1:1 floor plans.

For that reason, this page distinguishes among:

• historical sources;

• peer-reviewed research;

• industry datasets;

• institutional precedents;

• conceptual models;

• Big Floor Plans-developed tools;

• first-party BFP project evidence.

Unless a source explicitly studied Big Floor Plans, external research cited on this page should not be interpreted as proof that a Big Floor Plans walkthrough prevents a change order, eliminates rework, guarantees savings or produces a particular return on investment.

An outbound citation identifies the source for a claim.

It does not imply that the cited organization endorses Big Floor Plans.