Moisture Meter

Under the standards of professional home inspections, a home inspection is a non-invasive visual inspection. One device that has become common for non-invasive testing is hand held moisture meters which can help home inspectors look for hidden moisture behind the surface of a shower surround or wood deck finish.


GE Protometer Surveymaster

The GE Protometer Surverymaster is a very common model of moisture meter for home inspectors and is the tool we carry at Solid State Inspections. It costs around $500-600 at various online tool websites which is a small investment which generates impressive results for clients. 


The Surverymaster uses non-invasive sonar to look under the surface of a finish for dense moisture that may be hiding underneath. It reports the moisture level on a green-yellow-red scale and with a precise moisture level percentage on the display. This non-invasive moisture test is ideal for bathrooms (showers, bathtubs, around toilets) and on decks and balconies where the surface finish may not be showing signs of water penetration but water has done damage underneath.


The GE Surveymaster's last feature is a set of prongs hidden under the top lid that can be used for a direct moisture level reading. The home inspection standards do allow for 'sample probing' by home inspectors where inspectors feel there may be signs of deterioration. The prongs on the Surveymaster allow for precise moisture reading options where sampling may be required.


What Moisture Level is a Concern?

Wood rot and mould will grow when there is warmth (over 5 Celsius), food (like wood or paper-backed drywall), and moisture. It only takes 15% moisture levels in our homes for rot and mould to begin to grow. A dry home will typically have less than 8% moisture in the building materials. If moisture levels are between 8-15%, there may be some source of moisture penetration the scanned area this may require further investigation or monitoring by the home owner. Levels over 15% require further, and likely destructive, investigation by the homeowner to repair.


False Moisture Meter Results

Home Inspectors need to be aware of conditions that will give a false meter reading. Metal flashing under a vinyl surface on a wood deck will cause the meter to go off the scale. Concrete will also provide a very high false reading which makes the moisture detector unusable on a concrete structured deck.


The most common 'false alarms' for home inspectors are in shower surrounds and bathroom floors. A quality shower surround will use a waterproof concrete backer board behind the tile which will provide a false reading of high moisture levels. Also, concrete skim coats under tile floors can create false readings for home inspectors trying to detect toilet leaks on the floor. Real moisture damage is typically very uneven and tends to get worse the lower down you scan as water follows gravity. If you are getting a consistent level of high moisture readings all over the scanned surface, it may be a false alarm.


Moisture Meter Controversies

There are two controversies about using moisture meters in home inspections:

  • Use of Tools - The home inspection industry is a 'visual' inspection meaning no tools need to be used in the inspection process, and there are some inspectors who adhere to this very strictly. There are also some home inspectors who argue that we already carry screwdrivers to remove electrical access panels, which we are required to inspect, so we are not truly tool-free. Our view at Solid State Inspections is that moisture meters, like flashlights, ladders, and binoculars, are a non-destructive visual aid the inspector.
  • Legal Risk - Carrying a moisture meter increases the legal risk to home inspectors that they may miss something in the home that the moisture meter could have detected if it was used everywhere. To avoid missing anything with the moisture meter, one option is to adhere to the 'no tools' standard and avoid the liability risk. There is however another legal argument called 'standard of care' that says every inspector needs to perform their services to the 'normal' standards of the industry. As so many inspectors carry and use moisture meters, inspectors who choose not to use them may not meet the 'standard of care' for their clients. One way to mitigate the legal risk of missing anything with a moisture meter is to be consistent and always use (or not use) the meter in the same places in all homes for all clients. Always consult a lawyer for legal advise but at Solid State Inspections, we choose to carry moisture meters and use them in bathrooms, balconies, and surfaced decks in every home we inspect.


Final Thoughts

The use of moisture meters in home inspecting is a good thing to help protect home inspection clients from potentially thousands of dollars in hidden expenses. While industry standards may not 'require' these tools for home inspections, the common use by many home inspectors suggests that they have become industry norms for use and should now be in the tool kits for all home inspectors.


By James Bell - Owner/Operator of Solid State Inspections Inc.