Structural drying 101 for insurers

There is a  prevailing belief that it should only take a knowledgeable contractor three or four days to dry a structure. While it is possible to dry a structure in that timeframe, it is extremely rare to do so. Just because someone tells you it is dry does not mean it is. Just because some materials are dry, does not mean all of them are dry. Is it possible that you are being told only a portion of the truth?

Restorers are responsible for drying structures, and carriers are responsible for paying the bill. However, the work should be necessary or supportable.

What is Dry?

Dry Standard — The Institute of Inspection Cleaning and Restoration Certification (IICRC) actually identifies what you call dry with the term “dry standard.” The definition section of the IICRC S500 2016 describes dry standard as “a reasonable approximation of the moisture content or level of a material prior to a water intrusion.”

So how do we find our dry standard? The standard continues, “An acceptable method is to determine the moisture content or levels of similar materials in unaffected areas or use historical data for the region.” In other words, dry standard involves pre-loss moisture levels in the structure, and they can be found by locating unaffected materials in the structure and getting the target values from there. Basically, you are comparing readings from the inside wall to other inside walls. A wood floor would be compared to other wood floors, and so on.

What happens if you cannot find anything dry? The 2016 S500 standard has a chart that details what your target should be. There you will find an Equilibrium Moisture Content (EMC) table which tells us, for example, that a house that is 70F and 50% Rh would have most softwood framing materials at an approximate EMC around 9.2% wood moisture equivalent (WME). Often when you are told that 16% or 20% is an acceptable dry standard, it’s a misrepresentation of the standard.

The standard says that no matter what EMC you get from the materials in the house, you cannot leave a material at an EMC that would support microbial grow — and 16% is documented to support growth. It also says that an acceptable dry standard is within 10% of what the other similar materials in the house were pre-loss.

So think of that 9.2% material we discussed earlier. An acceptable goal is 9.2% + .92% or up to 10.12%. If this sounds way low, and you are pushing your contractors for an arbitrary value not tied to the structure, you may be inadvertently asking them to violate the standard, failing to return the loss to its pre-loss condition and leaving conditions that may or may not support microbial growth. You also now own that project and any outcomes your decision creates.

Now, let’s discuss meters and how they work. An accurate dry standard without thorough materials surveys can still leave a structure very wet.

Moisture meters 101

When someone says that a material or house has been moisture mapped and is dry, what they are usually saying is that their meter gave a reading they view as acceptable for dry. But is it?  How do you know if they have really done a complete job? Depending on the type of meter they used, they could have completely measured all of the materials or taken shallow readings in the wrong locations. Knowing where to look and what meters reliably tell you makes all the difference.

For example, non-penetrating meters only measure one-half to three-quarters of an inch into assemblies. A standard interior wall is 5½ inches thick. Using a meter that only measures the first half-inch of the assembly means you don’t know if the rest of the assembly is wet or dry. How much is wet and how long it takes to dry is the issue. Measure inaccurately here and we develop a belief structure that does not match reality, such as thinking a structure can be dried in three or four days.

Speaking “meter”

A little foundational information will be helpful to frame this discussion. Here is a brief overview of the different types of meters and their uses.

Non-penetrating meters

If you were to review the specifications of non-penetrating meters, you would find that the vast majority of them penetrate only a half to three-quarters of an inch into the material being surveyed. There are two types of sensors in these non-penetrating meters — radio frequency and impedance. Here’s how they work.

Radiofrequency meters

Radiofrequency is just what it sounds like, an RF signal that surveys a material. For those of you who have used a meter, a good example is a GE Survey Master on the “Relative” setting. It measures the material it is in contact with from the sensor point down into the material and provides a relative reading on a scale, such as 20 on a scale of 100.

Basically, it only averages its readings in this mode, meaning it could be saturated in the middle of that piece of wood and dry on the top and still give you a 12% reading. Why is that a problem? Because the moisture locked in the middle of that wood will not stay there. It will seek equilibrium with everything around it.

If you believed that reading and declared the material at dry standard, covered it with drywall, paint and trim, all you have to do is wait a couple of days and you will have created your very own mold farm. All that trapped moisture will equalize and, in most environments, microbial growth will begin in the wall cavities within 24 to 48 hours.

Impedance meters

An impedance meter uses a small electrical current passed between two fixed points to measure resistance. An example would be a Tramex Moisture Encounter. It, like the RF meter, gives a reading on a relative scale (20 of 100). And, just like our RF meter earlier, we get the same type of curving sensor reading depths. We also get the same averaging issue referenced earlier, so very wet materials can appear dry due to the limitation of the survey depth.

Now that we understand these technologies are limited by penetration depths of one-half to three-quarters of an inch, and they average the readings across the entire thickness of the assembly, you need to know about their next limitation — insulating barriers.

Insulating barriers

In both RF and impedance meters, the readings are further limited by any insulating barriers (i.e., air gaps between trim and drywall, air gaps between drywall and base assembly). Neither electrical current nor RF can bridge the gap created by voids of air. The accuracy expected by putting a meter on top of a half-inch section of trim would be limited to the average of the first half-inch, meaning we know nothing about the drywall behind it or the wood assembly behind the drywall. Without that information, you’re exposed to liability.

The next logical conclusion is relying on a non-penetrating meter to clear assemblies that can leave all parties at risk. You’ll never know if there was elevated moisture content in the remainder of the wall or if there are pockets of moisture left in the wood or concrete building assemblies.  Spoiler alert, there is, and lots of it. And many if not most of these projects are coming from preferred vendors.

Too often restoration contractors are not given the tools, knowledge or consent to completely dry a house. The end result is a re-dry, a Category 3 microbial remediation and then a much larger restoration phase. All of this is done while the insured collects additional living expenses (ALE) residing outside of the structure. Half-drying houses costs an enormous amount of unnecessary money, and much of the confusion that leads to this increased severity is due to incorrect use of non-penetrating meters.

Now that we have established a non-penetrating meter will only penetrate one-half to three-quarters of an inch and not past any air or other insulating gaps, what are the chances that contractors using almost exclusively non-penetrating meters have left structures they have addressed wet? Since the entire industry is doing this, and even if a company doesn’t have to pay for the remaining damage under the current claim, the damage lives on to the next carrier and will need to be resolved at some point when uncovered. Proper use of penetrating meters could address the issue for everyone.

Penetrating meters

Penetrating meters, when coupled with a pair of 3.5-inch stainless steel screws, confirm whether or not the entire assembly is dry. The same impedance sensor technology used earlier is reused here, but with an important difference. While the non-penetrating impedance meters measure resistance between two pads and average at a depth of one-half to three-quarters-inch, this setup utilizes penetrating probes or “pins.” If it’s wet anywhere between those points, you know it.

Restoration/mitigation contractors are responsible for returning the structure to its pre-loss moisture content and doing it in a way that doesn’t support secondary damage (i.e., microbial amplification or heat damage).  Carriers are required to return a property to its pre-loss condition as well, so we should be in agreement — if you want to find the moisture in materials, a penetrating meter provides the most accurate readings.

Structural drying

So, how long does it take to dry a structure? It depends on how deeply and completely you survey your materials and what meter technology is used to determine if dry standard was obtained. What shows dry with a non-penetrating meter at day four, shows wet for 7-12 days with the use of 3½-inch screws and a penetrating meter. Why should the remaining water matter? Does it really matter in the long run? The short answer: Yes! Structures left wet can carry huge mitigation, remediation and restoration scopes, not to mention the cross-contamination to the contents and ALE incurred during the additional required work.

The carrier can accomplish the complete drying of the structure, control severity, and allow for carrier and contractor profit. Contractors, like the vast majority of insurance companies and adjusters, are honorable people trying to do right, be profitable and make the insured whole. If we can get structures thoroughly moisture mapped, completely dried, reported accurately and billed based on what the science determines needed to be done, we cannot only coexist but grow relationships that serve all parties — starting with our mutual clients.

As an ex-independent adjuster, state-certified general contractor, State Certified Mold Remediator and Mold Assessor, triple IICRC Master, WLS, CMP, CIES, CIEC, CMRS, CSDS, & CSFS,  R. David Sweet’s 20+ years of industry experience allow for a unique perspective of the restoration industry and claims environment. He is an admitted subject matter expert in the areas of mitigation, mold remediation, microbial assessment, building envelope, fire/smoke damage and project pricing. Contact him at (david@mitigationconsulting.com).

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