- What the Nine Domains Are, and What They Are Not
- Exam Format Behind the Domains
- Domains 1-3: Water Science, Site Drainage and Foundations
- Domains 4-5: Walls, Ceilings, Floors, Roofs and Envelope Assemblies
- Domains 6-7: Plumbing and HVAC
- Domains 8-9: Structural Drying and Project Documentation
- Reference Map and Ethics
- Sequencing the Domains in Your Prep
- Eligibility, Fees and Renewal in Brief
- Frequently Asked Questions
- CMCI means Council-certified Moisture Control Investigator, issued by the American Council for Accredited Certification (ACAC), not the Construction Manager...
- ACAC's chart lists nine official domain lines, from The Science of Water through Project documentation, but publishes no percentage weights.
- The exam is 100 multiple-choice questions in three hours, closed book, with a 75% passing criterion.
- The handbook groups content differently than the chart, so study the chart's nine lines plus the ACAC Code of Conduct.
What the Nine Domains Are, and What They Are Not
The Council-certified Moisture Control Investigator credential is administered by the American Council for Accredited Certification, and certification decisions are made by its CMCI Certification Board. The nine content areas in this guide come from ACAC's document "CMCC and CMCI Examinations," approved March 6, 2024. The CMCI lines in that chart are official examination objectives. If you are new to the credential itself, start with What Is CMCI Certification? before working through the domain list.
Be precise about what the nine domains are. They are objectives from an unweighted chart. ACAC does not publish a percentage for each domain or a count of questions per domain, so any source that tells you "Domain 4 is 18% of the exam" is inventing a number. This guide will not do that. Instead, it treats the domains as a map of topics you must be able to reason about, then ranks effort by your own gaps rather than by invented weights.
Also keep CMCI separate from CMCC. The two credentials share a handbook and a domain chart, but CMCI has its own eligibility rules and exam details. Do not carry CMCC facts, statistics or fees over to CMCI preparation. For the full requirements picture, see CMCI Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Exam Format Behind the Domains
Knowing how the exam is delivered helps you decide how to practice each domain. The facts below come from ACAC sources:
| Item | CMCI Detail |
|---|---|
| Questions | 100 multiple-choice, at least four answer choices each |
| Time | Three hours |
| Materials | Closed book |
| Passing criterion | 75%, set by the certification board using a modified Angoff method |
| Delivery | Testing center or online video-proctored, via Kryterion |
| Question order | Randomized question and answer order |
| Results | Immediate |
Because questions are randomized, you cannot predict which domain appears when. Closed-book delivery means you need working recall of instrument behavior, drying principles and building-assembly logic, not just the ability to look things up. Online candidates must supply a computer, an approved webcam, a private location and a continuous 2 Mbps upload and download connection. The CMCI Passing Score guide explains how the 75% criterion works, and the CMCI difficulty guide covers how to judge your readiness.
Domains 1-3: Water Science, Site Drainage and Foundations
The first three domains build the physical logic that every later domain depends on. An investigator who cannot explain how water moves cannot credibly locate where it entered.
Domain 1: The Science of Water
This is the conceptual base. Expect questions that ask you to reason about how moisture behaves in and around buildings.
- States and movement of moisture: liquid water, vapor and the conditions that drive each
- Humidity and temperature relationships, including why surfaces condense
- Why a single reading rarely proves a source, and what corroboration looks like
Domain 2: Site Drainage
Moisture problems often begin outside the structure. This domain connects grading and runoff to interior symptoms.
- How surface water is directed toward or away from a building
- How drainage failures can show up as basement, crawlspace or slab-level moisture
- Observations that point to an exterior cause before you look inside
Domain 3: Foundations
Foundations sit at the boundary between soil moisture and the building interior.
- Common foundation types and their characteristic moisture pathways
- Distinguishing groundwater intrusion, condensation and plumbing leaks that look similar
- Choosing the next investigative step when readings are ambiguous
A useful way to study these three together is scenario-first. Take a symptom, such as damp lower walls, and write out the observations that would separate a drainage cause from a foundation cause from a condensation cause. That habit is the same reasoning the exam rewards.
Domains 4-5: Walls, Ceilings, Floors, Roofs and Envelope Assemblies
These two domains cover the building assemblies where hidden moisture lives. They are also where instrument interpretation matters most.
Domain 4: Walls, ceilings, and floors
Interior assemblies hide moisture behind finishes, so your conclusions must rest on more than a surface reading.
- How moisture meters and infrared imaging are used, and the limitations of each
- Why a thermal anomaly or a meter reading is a lead to corroborate, not a conclusion
- Corroborating observations: staining, odor, material condition, location relative to likely sources
Domain 5: Roofs and building envelope assemblies
The envelope is the first line of defense against bulk water and a major route for vapor movement.
- How roof and envelope failures translate into interior moisture patterns
- Interactions between assemblies, such as wall-to-roof transitions
- Tracing an interior symptom back to a plausible envelope entry point
If you want to build the instrument side of your knowledge, the CMCI Cheat Sheet is a good place to consolidate must-know facts for quick review, and the CMCI Study Guide shows how to fold these assembly topics into a full preparation plan.
Domains 6-7: Plumbing and HVAC
Mechanical systems are both sources of moisture and potential explanations for it. These domains test whether you can tell a system-driven problem from an envelope-driven one.
Domain 6: Plumbing
Supply, drain and fixture failures are among the most common causes of interior water damage.
- Typical plumbing failure patterns and where they leave evidence
- Separating an active leak from historic damage or from condensation on cold lines
- Deciding what to inspect or test next to confirm or rule out a plumbing source
Domain 7: HVAC
Heating, cooling and ventilation systems control humidity and can introduce condensation or moist air to a structure.
- How equipment, ductwork and airflow can create or relieve moisture conditions
- Condensation and humidity patterns that originate with the mechanical system
- How HVAC findings interact with building assemblies and drying decisions
Note that the handbook does not separately label Plumbing, even though the chart does. Study it as its own domain anyway, since the chart lists it explicitly.
Domains 8-9: Structural Drying and Project Documentation
The last two domains turn investigation into action and record. They are where field experience tends to help the most.
Domain 8: Structural Drying
This domain covers how water-damaged structures are dried, and it ties directly to the prescribed drying text.
- Principles of controlled drying and how conditions are monitored
- Using readings over time to judge whether drying is progressing
- Connecting drying decisions to earlier findings about source and affected assemblies
Domain 9: Project documentation
An investigation is only as useful as the record it leaves.
- Capturing observations, readings and reasoning so conclusions can be reviewed
- Separating what was observed from what was inferred
- Reporting limitations honestly, including instrument limits and unverified areas
Documentation is also personal for candidates: the application itself requires four project sheets, so practice describing investigations clearly before you sit the exam. The CMCI Training overview covers optional preparation routes, and a prep course is optional rather than required.
Reference Map and Ethics
ACAC identifies required references. Match each to the domains where it does the most work:
| Reference | Best Used For |
|---|---|
| ACAC Code of Conduct | Ethical duties; required knowledge in addition to the nine domain lines |
| EPA, Moisture Control Guidance for Building Design, Construction and Maintenance (December 2013) | Water science, drainage, foundations, assemblies, HVAC |
| Ken Larsen et al., Leadership in Restorative Drying (fourth edition, 2014) | Structural drying and related documentation practice |
Key Takeaway
Read the complete prescribed references rather than only the pages highlighted in the handbook. The handbook's selected review pages supplement the full texts and do not establish exhaustive exam coverage. Also note that a vendor describes the drying book as a 2014 Gold Edition while the handbook says fourth edition; do not assume the two labels are equivalent without checking which copy you are using.
Sequencing the Domains in Your Prep
Since no domain weights are published, order your study by dependency rather than by invented percentages. Foundational reasoning comes first, then assemblies, then mechanical systems, then action and record. Here is one sequence tied directly to the nine domains:
Water, Site and Foundations
- Read the EPA guidance for Domains 1-3
- Write symptom-to-cause scenarios linking drainage and foundation observations
Assemblies and Instruments
- Cover Domains 4-5 with emphasis on meter and infrared limitations
- Practice stating the corroborating observation for each instrument finding
Plumbing, HVAC and Drying
- Work Domains 6-8, reading Leadership in Restorative Drying in full
- Compare plumbing, HVAC and envelope explanations for the same symptom
Documentation, Ethics and Review
- Review Domain 9 and the ACAC Code of Conduct
- Take closed-book practice questions under a three-hour limit
When you are ready to test yourself, try the free questions on the CMCI Exam Prep practice test site. Treat any practice set, including third-party previews, as a way to find weak domains rather than as proof of complete coverage; partial previews do not establish that a resource matches the real exam. Your readiness check is simple: can you explain, without notes, why you would verify a meter reading before concluding that moisture is hidden in a wall? If not, return to Domains 4 and 5.
Eligibility, Fees and Renewal in Brief
Domain mastery is only one part of the credential. Eligibility comes first: a high-school diploma or GED plus two years of documented relevant moisture-control field experience, or a qualifying two-year postsecondary degree or equivalent 15 qualifying science-related credits plus at least one year of relevant experience. The application includes four project sheets, applicable transcripts and verifications, followed by examination and unanimous certification-board review. The handbook also requests employer affidavits.
Be aware that ACAC's own sources conflict on some application details. The current application page references six months and online or email verification, while the handbook references 90 days and notarized application or employer-affidavit instructions. Board meetings are described as every four to six weeks on the application page and approximately every four weeks in the handbook. Confirm the current process directly with ACAC before you submit, and see CMCI Exam Dates for scheduling.
Cost for the initial US/Canada fee is USD 500, made up of USD 100 for the examination and USD 400 for certification covering the first two-year term. The current official application quotes USD 525 outside the US/Canada, and a retake costs USD 100. The CMCI Certification Cost breakdown goes through the pricing in detail.
The certification is valid for two years. Renewal costs USD 400 and requires 40 renewal credits, comprising 10 for continued field activity plus 30 professional-development hours under current procedures. Keep your records, because they can be audited.
On the question of value, ACAC's 2025 Exam Pass Ratio document contains no CMCI row, and that omission is not a zero pass rate. For realistic expectations about pay and return, read the CMCI Salary Guide and Is the CMCI Certification Worth It?, keeping in mind that moisture-investigation roles are not the same as construction-manager roles or broad occupational averages.
Frequently Asked Questions
ACAC's chart lists nine official domain lines for CMCI: The Science of Water, Site Drainage, Foundations, Walls, ceilings, and floors, Roofs and building envelope assemblies, Plumbing, HVAC, Structural Drying and Project documentation. The ACAC Code of Conduct is additional required knowledge.
No. ACAC publishes no percentage weights or per-domain question counts, so avoid any source that quotes them. Distribute your effort by dependency and by your own weak areas.
The exam has 100 multiple-choice questions with at least four answer choices, a three-hour limit and closed-book rules. The passing criterion is 75%, set by the certification board using a modified Angoff method.
The handbook's CMCI section lists seven technical headings plus the ACAC Code of Conduct and does not separately label Plumbing or Project documentation. No issuer statement resolves the difference, so study all nine chart lines plus ethics.
No. Here, CMCI means Council-certified Moisture Control Investigator, issued by ACAC. Construction-manager credentials from other organizations are separate, so keep their policies and details out of your preparation. For more background, see What Does CMCI Stand For?