How Do Pros Know It's Actually Dry? Moisture Readings Under Tubs and Vanities After a Flood
Crew says there's no moisture under the tub or vanity? How pros measure and map moisture, what "dry" really means, and how to verify it yourself.
A professional drying crew knows a material is dry when moisture readings match the same material in an unaffected part of the home, not when it feels dry. On Keystone jobs, every affected area is moisture-mapped: each reading is recorded on a floor plan from day 1 until it hits the dry standard. Every reading is checked with a meter. If your crew says there's no moisture under the tub or vanity, the readings on the map should show you why.
Want your drying checked? Call 24/7 · (801) 948-2501.
What does "dry" actually mean?
The industry standard for water damage, the IICRC S500, uses a dry standard: a reasonable approximation of a material's moisture level before the water intrusion. Restorers find it by measuring similar materials in unaffected areas of the same structure. The drying goal is the target the crew dries to, at or near that standard.
That means "dry" is different in every house. Drywall in a Salt Lake basement and drywall in a humid coastal condo have different normal readings. That's why good crews take a reference reading in your home instead of using a generic number.
How do pros measure moisture?
On Keystone jobs we use a Protimeter MMS3 moisture meter. It takes both:
- Pin readings, where probes go into wood or drywall for a direct moisture reading at depth
- Non-invasive readings, which scan surfaces like tile, flooring or drywall without damaging them
We also take air readings (temperature and humidity) in affected rooms, unaffected rooms and outside, so we know whether the equipment is actually pulling water out of the air.
Every reading goes on a moisture map: a floor plan marked with each measurement point, logged daily. That's how we know when an area is done and can show it to you, your adjuster or your property manager.
Keystone always does a final check. Before a job is closed out, we go back and re-read every mapped point. On a recent job in Sugar House, we dried the structure for 4 days. Asbestos work had to happen after that, so we went back and re-checked every area before anything was closed up. Everything still read dry. Drying can be undone by later work, a new leak or a missed pocket of water, so the final check is what proves it's still dry.
At the end of every job, the customer gets a final report with photos of the meter readings on every dried material.
How can there be no moisture under the tub or vanity?
It's possible, and it often happens:
- Water follows gravity and the path of least resistance. It may have run across the tile and down into the unit below without ever getting under a tub that's sealed or sitting on a mortar bed.
- Tubs and vanity bases can block water. A well-caulked tub apron and a solid vanity base can keep water out of what's underneath.
- Tile removal opens things up. Once the tile is up, the subfloor dries faster, and readings from those areas can drop quickly.
But "no moisture" should be measured, not assumed. Pros check under tubs and vanities by:
- Taking readings through the toe kick or vanity bottom, or removing the toe kick to reach the subfloor
- Checking the subfloor and wall bottoms right next to the tub
- Using an access panel to reach the drain side of the tub, if there is one
- Comparing all of it to a reference reading from an unaffected area
How can I verify it myself?
Ask your restoration company:
- "Can I see the moisture map?" You should see each point, the daily readings and the dry standard.
- "Where did you take the reading under the tub and the vanity?" It should be marked on the map.
- "What's the reference reading, and where was it taken?"
- "Were readings logged every day?" Daily monitoring is standard practice in professional drying.
If they can't answer with numbers, ask for a reading in front of you before anything is closed up.
What should a final drying report include?
| Item | What it shows |
|---|---|
| Moisture map | Every reading point, marked on a floor plan |
| Daily readings | Progress from day 1 to dry |
| Reference reading | The dry standard each material was measured against |
| Final check | A re-read of every point before the job closes |
| Meter photos | Photo proof of the final reading on each material |
Questions about your drying readings? Call 24/7 · (801) 948-2501.
Questions about your specific situation? Talk to us — advice is free, 24/7.