WLFI Moisture Testing & Subfloor Preparation 3

Question 1

An inspector uses a pin-type moisture meter on a plywood subfloor and gets a reading of 15%. What should the inspector do next?

Accepted Answer

Verify the reading using a calibrated secondary test method

Answer

A single meter reading should be verified with a secondary method because pin meters can give false readings depending on species and temperature.

Question 2

What does a pinless (electromagnetic) moisture meter measure compared to a pin meter?

Accepted Answer

It detects moisture based on changes in electrical capacitance rather than resistance

Answer

Pinless meters use electromagnetic fields to detect changes in electrical capacitance caused by moisture, allowing non-invasive scanning without penetrating the surface.

Question 3

When is it necessary to test concrete slabs that are built above grade (i.e., elevated slabs) for moisture?

Accepted Answer

Always, because elevated slabs can still trap and emit moisture vapor

Answer

Elevated slabs can still accumulate and emit moisture vapor, especially if they were exposed to weather during construction or contain residual mix water.

Question 4

Per ASTM F2170, how deep should the RH probe hole be drilled in a concrete slab of 4-inch thickness when the slab is drying from one side only?

Accepted Answer

40% of slab depth (approx. 1.6")

Answer

ASTM F2170 requires drilling to 40% of slab depth for slabs drying from one side, which represents the equilibrium point for moisture distribution.

Question 5

Which type of subfloor panel is most resistant to moisture-related swelling and is preferred in high-humidity environments as a subfloor for wood flooring?

Accepted Answer

Tongue-and-groove plywood rated Exposure 1

Answer

Exposure 1 tongue-and-groove plywood resists delamination and swelling better than OSB in high-humidity subfloor applications.

(WLFI) Wood and Laminate Flooring Inspector Practice Test

(WLFI) Wood and Laminate Flooring Inspector Practice Test

WLFI Moisture Testing & Subfloor Preparation 3