Quick answer: A job is dry when every numbered reading point matches its dry standard: the reading from unaffected material of the same type, taken with the same meter. Until then, log daily the material readings at the same points; temperature, RH, g/kg and dew point indoors, at the dehumidifier outlet and outdoors; the equipment running; and condensate collected.
Quick answer: record every day
- Material readings at the same numbered points, vs the dry standard.
- Air: temperature, RH and moisture content inside, at the dehumidifier outlet, and outdoors.
- Equipment: what is running where, and condensate collected.
A water damage drying log (also called a moisture map or psychrometric log) is the daily record that shows a structure was dried.
(Here "log" means a record. For drying timber logs, see industrial material drying rooms.)
Day 0: set up the log
- Source and category: where the water came from, when it started and stopped, and whether it was clean, grey or contaminated.
- Sketch: rooms affected, with walls, floors and ceilings marked, and every reading point numbered (W1, W2… for walls; F1… for floors).
- Dry standard: for each material, take a reading in an unaffected area of the same building with the same meter. That is the target.
- Initial readings at every point.
- Equipment placed: number, type and location of dehumidifiers, air movers, heaters.
The daily record
| Field | Example |
|---|---|
| Date and time | 12 Mar, 09:30 |
| Technician | Initials |
| Outdoor: temp / RH / moisture content | 14 °C / 82 % / 8.2 g/kg |
| Affected room: temp / RH / moisture content | 24 °C / 48 % / 9.0 g/kg |
| Unaffected room (reference) | 21 °C / 45 % / 7.0 g/kg |
| Dehumidifier outlet: temp / RH / moisture content | 30 °C / 22 % / 5.8 g/kg |
| Material readings | W1: 28 → dry standard 12; F1: 95 → dry standard 15 |
| Condensate collected | 18 L since last visit |
| Equipment changes | Removed 1 air mover from room 2 |
Use the same meter, scale and contact method at each point every day; readings from different meters or scales cannot be compared.
Drying log vs drying report
| Document | What it is | Who uses it |
|---|---|---|
| Drying log (dry log) | The day-by-day record of readings, equipment and changes | Technicians on site |
| Moisture map | Floor plan with marked reading points and values | Technicians, adjusters |
| Drying report | Summary at completion: source, category, affected materials, equipment days, readings over time, final readings vs dry standard, photos | Customer, insurer, builder |
In water mitigation, "dry logs" are the evidence that structural drying is complete: that walls, floors and framing reached their dry standard before rebuild.
Structural drying: what the log must show
- The dry standard for each material, taken from an unaffected area of the same material.
- Daily readings at the same marked points, with the same meter and scale.
- Atmospheric readings (temperature, RH, moisture content) outside, in the affected area, in a reference area and at the dehumidifier outlet; the difference between affected-area and outlet moisture content (grain depression) shows the dehumidifier is working.
- Equipment placed and removed each day, with reasons.
- When each material reached its dry standard.
Reading the trend
| What the log shows | Meaning | Action |
|---|---|---|
| Room moisture content well above outdoors and reference | Moisture being released; drying working | Continue |
| Outlet moisture content only slightly below room | Dehumidifier not removing much (cold room, iced coil, undersized) | Warm the room, check the unit, add capacity or switch to desiccant |
| Material readings falling steadily | On track | Continue; remove air movers from dry areas |
| Readings stalled for 2+ days | Hidden water, trapped layers, poor airflow | Open cavities, lift coverings, re-aim air movers |
| Condensate volume falling day by day | Less water left to remove | Normal as drying finishes |
| Room moisture content rising | Outdoor air entering or new source | Close openings; check for new leaks |
Air moisture is often recorded in grains per pound (gpp) in the US; 1 g/kg ≈ 7 gpp. The grain depression (room minus dehumidifier outlet) shows how hard the dehumidifier is working.
Closing the job
The job is dry when:
- every reading point is at or within the agreed margin of its dry standard;
- the room's moisture content is back near the unaffected reference;
- no new wet areas appear after equipment is switched off for a day (where practical).
Record the final readings, photos and the date equipment was removed. Industry practice for water damage restoration follows the IICRC S500 standard; the US EPA's guidance covers drying within 24–48 hours to limit mold (US EPA, Mold course chapter 4).
Equipment notes for the log
- Refrigerant dehumidifiers: efficient in warm rooms (above about 15–18 °C). Our commercial portable dehumidifiers remove 60–138 L/day at 30 °C / 80 % RH.
- Desiccant dehumidifiers: keep working in cold, unheated buildings and reach lower humidity for dense materials; see desiccant dehumidifiers for water damage restoration.
- Air movers: across wet surfaces, overlapping; remove them from areas that reach dry standard.
Related: drywall drying times, drying concrete after a leak.
FAQ
Frequently asked questions
What is a drying log in water damage restoration?
A daily record of moisture readings, air conditions and equipment that shows how the structure was dried and when it reached its dry standard.
What is a dry standard?
The moisture reading of the same material in an unaffected area of the building, taken with the same meter. Wet materials are dried until they match it.
How often should drying readings be taken?
At least daily, at the same points, with the same meter.
How is drying progress recorded?
By daily readings at fixed, marked points on each wet material, compared with the dry standard, plus atmospheric readings and equipment changes in a drying log.
What is a water damage drying report?
The completion summary of the drying log: affected materials, equipment, readings over time and final readings against the dry standard.
What is grain depression?
The difference in moisture content between the air entering and leaving the dehumidifier. A larger depression means the unit is removing more water.
Sources
- IICRC S500, Standard for Professional Water Damage Restoration.
- US EPA, Mold course chapter 4.
- ASHRAE Handbook—Fundamentals, Psychrometrics.
