Commercial Drying Specialist cheat sheet

Moisture content (MC) is expressed as a percentage of oven-dry weight: MC% = (wet weight − dry weight) / dry weight × 100; readings above roughly 16–20% in wood indicate conditions supporting fungal growth.

Wood equilibrium moisture content (EMC) tracks temperature and relative humidity; at 70°F, EMC is about 6.2% at 30% RH, 9.5% at 50% RH, and 16% at 80% RH - use these targets to judge whether a material is dry.

A pin-type meter reads electrical resistance between electrodes and is unreliable above about 28–30% MC; pinless (capacitance) meters read the average of the field under the pad and are skewed by the substrate beneath thin materials.

Always take both surface and penetrating (or edge) readings in wood; a dry surface over a wet core is a common false-negative after surface evaporation.

Thermal imaging locates temperature anomalies only; every anomaly must be confirmed with a moisture meter or pin probe because insulation voids, ductwork, and studs also create thermal contrast.

Document three readings per affected material per room (wet, dry reference, and boundary), plus photos and a sketch, so the drying record can prove the dry standard was met.

Category 1 water is sanitary; Category 2 contains significant contamination; Category 3 is grossly contaminated. Category and time since loss drive which porous materials are restorable versus removed.

Class of loss is set by the amount of water absorbed and evaporation load: Class 1 is minimal absorption with low evaporation, Class 4 involves deeply bound moisture in low-permeability assemblies such as hardwood, concrete, and cavity walls.

Inspect for hidden reservoirs before placing equipment: water trapped under baseboards, behind vinyl cove base, in wall cavities below the flood cut, and in subfloor layers.

Sequence: emergency mitigation (stop the source, extract, protect) → inspection and documentation → drying plan and equipment placement → daily monitoring → verification and sign-off → demolition or rebuild handoff.

Set the drying goal in writing before equipment is placed; the goal is the dry standard for the material and class, not a fixed number of days.

Equipment counts are derived from the drying plan: air movers per the manufacturer's coverage for the class, and dehumidifier capacity matched to the calculated evaporation load in pints per day.

Daily monitoring must record time, temperature, RH, GPP, material MC readings, and equipment status; a drying log without GPP or material readings cannot verify progress.

Change the drying plan when the log shows a flat or rising trend for 24 hours - add airflow, raise temperature, or open a cavity - rather than waiting out the schedule.

Assign a single accountable project manager for the drying chamber; split responsibility between mitigation and reconstruction crews is the most common cause of missed moisture.

Customer communication checkpoints: initial scope and expectations, daily or per-shift status, any change order for added equipment or demolition, and final verification with readings.

Close-out requires documented dry readings on all affected materials, equipment removed, and a signed certificate of completion that states the dry standard achieved.

The work authorization must state the scope, the drying standard, who pays, and the customer's right to stop work; get it signed before equipment is placed.

A change order is required whenever scope changes: added rooms, additional demolition, extra drying days, or equipment beyond the original estimate.

The drying log is a legal record; entries must be contemporaneous, legible, and include the instrument used and its calibration status.

Psychrometric calculations: GPP = (RH/100) × saturation vapor pressure at dry-bulb temperature, converted to grains; dew point is the temperature at which RH reaches 100%.

Daily evaporation load estimate: pints per day ≈ (initial MC − target MC) related to material mass, or use the industry rule that a Class 2 loss needs roughly 1 pint/day per 100 sq ft of affected area as a starting point.

Insurance documentation should separate mitigation (drying, extraction, antimicrobial) from reconstruction; carriers commonly deny drying charges not supported by daily readings.

Retain monitoring records, photos, signed authorizations, and equipment placement sketches per the contract and applicable statute of limitations.

Safety administration: confirm PPE, containment for Category 3, electrical load limits for air movers and dehumidifiers, and CO or refrigerant exposure controls before startup.

Drying is driven by three levers: increase evaporation (airflow and temperature), remove the vapor (dehumidification), and reduce the source (extraction and demolition).

Air movers should create a vortex or high-velocity boundary-layer flow across wet surfaces; stagnant air over a wet surface is the most common cause of slow drying.

Refrigerant dehumidifiers are most efficient above roughly 60°F and 40% RH; desiccant units are preferred in cool or low-humidity conditions and for deep cavity drying.

Target process air: keep GPP low inside the drying chamber relative to outside; if indoor GPP exceeds outdoor GPP, ventilate instead of dehumidifying.

Seal the drying chamber - close doors and windows, seal HVAC registers - so the dehumidifier is not drying the outdoors.

Open wall cavities at the flood cut and drill weep holes in vinyl cove base and behind cabinets to expose trapped water; moisture cannot diffuse through impermeable finishes.

Hardwood floors: use floor mats or injection systems with controlled heat and airflow; monitor MC daily and avoid rapid drying that causes cupping or checking.

Concrete: surface dry does not mean dry; use calcium chloride or in-situ relative humidity probes and allow roughly 30 days per inch of slab thickness for initial drying before assessing.

Verify completion with the dry standard for each material (e.g., wood at or near EMC for the space, concrete at the specified RH), not by elapsed days or appearance.