How to Get ASD Certification (IICRC Applied Structural Drying)

ASD is the second water damage credential in the IICRC ladder. It concentrates on the applied side of drying: reading the psychrometric conditions in the building, choosing the equipment that changes them, placing it, and proving with daily numbers that the materials are actually drying.

It sits on the same standard as WRT — the ANSI/IICRC S500 — but at a level of detail WRT does not reach.

• Psychrometry in depth. Temperature, relative humidity, grains per pound, dew point and the vapor-pressure differential that actually drives evaporation.
• Dehumidifier selection. Conventional refrigerant, LGR and desiccant units, and the conditions each one is the right answer for.
• Airflow. Air mover placement and count, and what changing airflow does to the surface boundary layer.
• Difficult assemblies. Wood floors, plaster, multi-layer walls and other materials that hold water tightly.
• Drying goals and documentation. Establishing the dry standard, setting the goal, and the daily record that supports it.

The underlying process is walked through on our structural drying page.

Yes. IICRC WRT certification is the prerequisite, and there is no way around it — ASD assumes you already know categories, classes and the basic drying model.

WRT is also the prerequisite for AMRT, the microbial remediation credential. If mold work is your next step instead, study for that exam at AMRTTraining.com.

ASD does not replace WRT and it does not renew it. They are two credentials.

Like WRT, ASD is taught by an IICRC-approved instructor and the exam is IICRC-administered and multiple choice. The difference candidates report is the equipment time — the class is built around applying the theory to wet structure rather than discussing it.

ASD is listed on iicrc.org as in-person only, which is consistent with a class built around equipment — a livestream camera can't show you how a plaster wall feels different from drywall under a moisture meter. The exam fee is $80, and a retest is also $80, as listed on the IICRC FAQs. Upcoming providers and dates are listed in the class directory, and if you're unsure whether ASD or something else is the right next step, our FAQ covers common sequencing questions.

Same structure as every IICRC credential: school-set tuition plus IICRC exam and renewal fees. ASD tuition can run above WRT where the class includes a hands-on facility and equipment.

The component-by-component breakdown is on the IICRC certification cost page. Tuition is published by each approved school, so compare what the fee includes rather than the headline figure.

Get comfortable with the psychrometry before you walk in, because the class moves quickly through it. If you cannot convert temperature and relative humidity to grains per pound and say what that means for evaporation, that is the gap to close first.

Use the free psychrometric calculators on real numbers from your own jobs, then drill the vocabulary with flashcards and test yourself with the practice questions.

Two common directions. Large-loss work points toward CDS, the commercial drying credential. Jobs where water sat long enough to grow mold point toward AMRT certification, which is governed by the S520 rather than the S500.

The full ladder is laid out in our IICRC certification guide, and our WRT vs ASD vs AMRT comparison walks through which one to take next depending on the work you're chasing. CDS lists WRT as its only prerequisite on iicrc.org, so it does not require ASD first.

A WRT-only tech follows the drying plan someone else wrote; an ASD tech is usually the one writing it. On a multi-room loss with mixed materials — carpet pad here, engineered wood there, a plaster ceiling above — the ASD-trained person is the one deciding equipment count and placement room by room instead of applying one blanket ratio to the whole house.

That shows up in daily monitoring too. A WRT tech records the numbers; an ASD tech reads them and changes the plan when a material isn't trending toward the dry standard, which is the difference between a job that dries in four days and one that stalls at day seven with no one noticing until the customer calls.

• Day 1–2: Re-run GPP, dew point and vapor pressure differential calculations until they're automatic, not looked up.
• Day 3: Walk through dehumidifier types — refrigerant, LGR, desiccant — and when each is the right call.
• Day 4: Review difficult assemblies: multi-layer walls, hardwood, plaster, and why they hold water longer.
• Day 5: Drill drying-goal and dry-standard documentation, since that's where exam questions get scenario-based.
• Day 6–7: Run the free practice questions cold, then review every miss before class starts.

1. Day 1 — psychrometry review and baseline math. The class re-establishes GPP, dew point and vapor pressure differential before moving into applied problems.
2. Day 2 — equipment selection. Refrigerant, LGR and desiccant dehumidifiers get compared against real conditions rather than a spec sheet.
3. Day 3 — hands-on placement. This is where the in-person format matters — you're placing equipment on wet assemblies and reading how each material actually responds.
4. Day 4 — difficult assemblies and documentation. Multi-layer walls, hardwood and plaster get worked through, along with the drying-goal paperwork that supports them.
5. Day 5 — exam. Multiple choice, IICRC-administered, covering the full week.

Exact schedules vary by approved school — some compress this into fewer days with longer sessions — so confirm the agenda with the provider listed in the class directory.

The most common one is showing up without the psychrometry already fluent. ASD assumes you can already convert temperature and relative humidity to grains per pound without stopping to think about it, and the class moves into applied problems immediately. Candidates who are still doing that conversion for the first time in class fall behind fast.

The second is treating ASD as a repeat of WRT's drying chapter instead of a different level of detail. WRT teaches that you dry a structure; ASD teaches how to justify every equipment decision with numbers. Candidates who expect a review class are surprised by how much of it is hands-on equipment work on genuinely wet materials.

The third is skipping the WRT prerequisite check before registering. Schools verify it's on file, and a candidate who assumes their WRT paperwork went through without confirming it can lose a seat in a class that only runs a few times a year in their area.

It shows up in the equipment log and the daily drying documentation, not as a line item on the invoice. An ASD-trained tech's file typically ties every dehumidifier and air mover placed to a specific reading and a stated reason, rather than a flat ratio applied to the whole loss.

That matters most when a carrier questions why drying ran longer than expected. A file that shows a material trending toward — or stalling against — the dry standard, with equipment adjusted in response, defends the extra days. A file with the same equipment count from day one to day seven with no adjustment noted invites a harder look.

It also affects difficult-assembly calls. When a hardwood floor or plaster wall isn't drying on the expected timeline, the ASD-trained justification for extending dry time or changing equipment is what keeps that decision from reading as padding on the file.