Unusual Home for this area has elevated levels

Just looking for some experience probably from our southern group. Our area is almost exclusivly housed with basements. I was called to a house recenlty due to musty odors. I preformed four air quality tests (one outside) and test results did show that the home has elevated levels of Aspergillus and Penicillium. This house is a one story ranch that is built on a slab and into a small hill. There is no basement. It appears that the floor joists rest directly on the slab. I am suspect of the wall built into the hill (the entire south side)but cannot see under the floor without drilling holes or cutting wood. I have not yet found the source of the mold and am looking for any ideas (preferably non destructive) for being able to see under the floor. The only vent (to the underside) I found is in the furnace room and the furnace is blocking my access. I am headed back on Thursday 9/13 with some ideas but I am always open to suggestions from others.




No expert on screed slabs
My total experience is 6
They ranged from late 40’s through the 80’s, at least one from each decade

What I do know is the ones I’ve seen had no vapor barrier, no post tension all were rebar, and all were wet.

This was due to moisture migration, air leaks at ducts we do a lot of AC here, and plumbing supplies entering through the slabs that did not have proper protection. Moisture meters and IR can point out these locations.

I’ve gotten some limited views from removing duct grills either at the floor or returns at walls.

What I do on suspect slab leaks is turn off all interior and exterior water fixtures at there everyday knobs.

Go to the meter and if the test dial is spinning you may very well have a leak.

I go back inside and start turning off service stop valves at the commodes one at a time, maybe just a bad flapper.

After all commodes are off if the meter is still running it’s time to call the slab leak pros.

Good luck!

Hi Scott,

That may well be a candidate for an Infrared camera inspection also a good moisture meter may tell you a lot.



Good advice!

Im just curious; at what point would one stop looking for the mold and call the experts? Sounds as if the initial work has been accomplished through the taking of the air samples. I am trying to understand where the line stops at doing mold sampling and starts becoming something more. What happens if you never actually find the mold? Is that the end of it or is there another step or protocol to follow?

ditto what Gerry said

A quote by the best known North American building scientist:

"If you see it or smell it, you do not have to test for it. It is more important to get rid of the mould rather than spend a lot of money trying to find out more about it***.***" (by sampling and identifying the species of mould- my comment)
Dr. Joe Lstiburek, P. Eng., Phd.; Building Scientist and principal at Building Science Corporation (Website: www.buildingscience.com)

Testing may have been an unnecessary step here!

Quite possibly, if a home smell musty & moldy you allready know it is going to have mold, the only real reason to take air samples is to establish a base line so that a post remeadiation clearance test has something to be judged against. The big issue here should be finding the cause of the moisture intrusion.



If you are called in to test for mold then you are required to look for red flags and then test to prove what you have found. As far as looking for the source of the mold did you see mold or did you just get air samples? The Lab will give you a report showing what it found which your nose may not be able to do. If the family has been sick then the report could be also used by a doctor. If I paid someone to come and test my house and all they did was walk in and sniff I may not be happy. If the joists are sitting on the slab and there is no moisture barrier between the slab and the wood then you have a problem.

Your mileage may vary…

Dick Moran
Clarksville, MD

All good information thank you for your input. And “yes” to the question just how far do I go? I took the air samples becuase the ederly ladies who live there asked me to. And I took more than normal as I was trying to create a base for later testing once the problem had been discovered. The other issue was that I could not see anything so I did the tests and the highest levels were in the family room which gives me a place to concentrate.

Now the next question does come…How far do I go, how much time do I spend and how much do I charge them for the time I spend there? Of course I made some money off of the tests. How many times do I go back to try to find the source? When do I call in the experts and am I not the expert?..Not on this type of construction that’s for sure.

My suspect at this point is the return ducts that, I believe, are utilizing the floor joists sitting on the slab…you know where this is going. I noticed when I turned on the furnace fan that the smell became stronger. One of the ducts may allow a mirror and flashlight. That is my next step tomorrow unless someone out there has any better ideas!!

Please check HVAC drain and air handler area

Mold heaven in my area area if stopped up

Don’t much in duct work

Don’t forget old fashion dirt - carpet and furnisher

If sometimes people let these things get out of hand an stuff starts to grow

Hopefully a good flashlight will find what you are looking for

Good luck


Hi Scott,

These questions are best answered before you even step foot into the place by establishing the scope of your services to the customer. Of course, this does not help you in this situation now–but something to ponder for the future. As far as charging for your time, come up with what your hourly rate is and then bill in 6 minute increments as other professional consultants would do.

It is highly possible when working on these cases that you will receive phone calls from the “specialists” and may even be requested to attend various 3rd party inspections where the destructive testing will occur. This is what seperates the inspectors from consultants. You need to decide if you will attend these events, which I do, and what you will charge for your time on an hourly basis. Then make sure the customer understands all of this and have them sign to put it in writing. These cases can linger on for years. I inspected a house in the fall of 2005 for a moisture intrusion situaiton and it was just finally resolved in the spring of 2007. I spend about 4 hours of actual inspection time on the property over two seperate occasions and logged about 10 hours of follow up time in the form of phone calls, and attendance at two third party inspections. All was billed back to the customer.


Two things you mentioned that triggered a memory… elderly ladies & furnace fan. You’re in WI so that implies that the furnace is in use a big part of the year. I know some elderly ladies up north that are very concerned with their wood furniture getting too dry in the winter.

Is there a humidifier by chance, on the furnace? Those things are professional level petri dishes.

Just left the “mold house” as I am now calling it (certainly not to the customer). There is no humidifier in the house, they are using a dehumidifier. In fact I asked them if they even needed one in the winter and they said no as I expected. The return ducts are not ducts at all just vents cut into the floor. The return air is sucked through these vents over the cold slab thus warming it and creating moisture. This moisture keeps the house at a good humidity level but must be destroying the floor joists that I cannot see.

I can see just enough to understand that the support is a series of 2 x 6 in a cross pattern to allow the air to flow in between the floor joists. A poor design at best but one they will have to live with. This house is built into a hill and about 4 feet of the North side is in soil. My suspect is this wall but there is no access to see anything. My next step is to contact another inspector who has a termal imaging device and see what we can using this. We also discussed using a media type filter with a UV light just to get them some relief from the poor air they are living in. Always willing to listen for other suggestions, opinions, etc.


How do you know it’s not soil-borne bacteria? I’d recommend a specialist and be out of there.
I’m with Gerry on the thermal imaging and Brian on finding out exactly what it is.

Find the source of moisture and correct it. If the smell continues, recommend an industrial hygienist.

Calcium Chloride test might be usefull.
ASTM F 1869


It sounds like you are trying to solve their problem for them with the recommendations. That was the point of my original post earlier. This is now “mitigation” of the problem and no longer inspecting. This is thin ice to be standing on unless you are trained in this area. There are all kinds of recommendations and even professional mitigators will not always agree what is the best action to take. Before you realize it you can become right in the middle of the problem with no good way to extract yourself. At some point the HI needs to know “when” to say “I have done all I can and now you need to call in the experts in this field.” I am playing devil’s advocate here because I see too many HIs who go out on limbs trying to be helpful and knowledgable but jump, not step, way outside their area of responsibility and get over into areas where they have no business. The HI should not try to “solve the problem” for the homeowners, buyers, because WHAT IF YOU ARE WRONG? Are you prepared for the possible consequences if what you suggests makes matters worse. SOPs are guidelines and many will argue they are the minimum standard, but they are there to provide the Inspector with a modicum of protection if adhered to. Once you go beyond the scope of a home inspection you open yourself up for all kinds of liabilities. Just some food for thought. As I always say, you can do what you want as it is your business and how you run it is your business. Good luck.

My thoughts as well Doug!

Good advice Doug

Well I am certainly not going to disagree with what you have said about when to step out, however they came to me looking for an expert. Am I not suposed to be the expert in mold assesment?

I am not going to tell them how to rid themselves of the mold, but I feel since I still have not found the source I have not done my job. Once the source is found it is up to them who they hire for remediation and how they go about it. I still feel it is my job to determine the source of the mold. I can walk in to a musty smelling house and tell them they have mold, charge them XX dollars and leave. I provide a service with the testing, besides I am getting one hell of an education at the same time. We will be going back on 9/25 with a thermal imaging camera.

At my suggestion they called one remediator and he asked where the mold was they told him they did not know yet, he said call back when you know. Obviuosly this one will not get the job.

Now to your point when to get out…this could be the hard part and I agree with all that you have said. Is this the proverbial rock and hard spot?:mrgreen:

As always I welcome comments and opinions from all,