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10:49 AM Tue, Dec. 11th

Recurring skunky odor stumps the pros

I received this email earlier this week:

"I live in Quailwood and our house is seven years old. I am at my wits' end over a smell in my house. It started last year with a terrible "sweet skunky" smell in our front guest bedroom. I called an exterminator thinking it was something dead (that's how strong it was). He came out and looked all around - nothing in the attic, the attic is sealed at the walls, no holes in or under the walls (we have a concrete slab floor). He was stumped. He told me to air out the room for a couple of days. I did, and the smell went away.

"Then in March of this year during a rainstorm, we developed the "sweet skunky" smell under our bathroom sinks. I called a plumber and he said it was definitely not a sewer gas odor, and he found no leaks. Then I called a different exterminator, but I got the same answer from him as the last guy. I braved it out and it finally went away... until last week, when it rained.

"The smell is in the bedroom again and stronger than ever. But this time I can locate it. On the outside wall it is really strong on one side, low on the wall, near an electrical socket. We are pretty sure there are no pipes in that wall; it's not wet inside or outside. I called another plumber. He said the same as the first plumber. Then we had an HVAC guy out and he said it was our neighbor's bushes. No way it's the bushes - purple sage doesn't smell like that!

"Could a skunk keep spraying the same spot near the bedroom and then go to the bathroom wall (on the same side of house) and spray? Would the smell only appear when it's humid? Any ideas what it might be or who I call before we start tearing up walls?"

It must be a strong odor if you have called two plumbers, two exterminators and an HVAC (heating/cooling) contractor. I would guess it's not a plumbing problem - that wouldn't account for the odor in a bedroom, and two different plumbers could not find a problem.

I am not a skunk expert. I do know they can spray to mark their territory, especially in the spring (mating season). I have inspected many crawlspaces (the area under the home, not the attic over the home) with a skunk odor. This is because skunks like to live in crawlspaces. I don't know why a skunk would spray the exterior walls of a home with a concrete slab floor unless he was living under something in the yard nearby. As far as I can tell, if there is a skunk odor, it will be there all the time and not get worse when it rains. In fact, I would think rain would eventually wash the odor off the exterior walls. And of course you had two different exterminators that did not find any signs of pest entry.

Without having seen the home, my next guess would be moisture in the walls. Moisture could be coming in from flashings around windows or other penetrations though the exterior walls, so it could be in rooms that don't have plumbing lines nearby. You said the bathroom and bedroom with the odors are on the same side of the home. Does this side of the home get more rain than the other sides of the home (e.g., wind-driven rain)?

You mentioned the odor was strong near an electrical outlet on the exterior wall. If there is moisture (mildew or mold) in the wall, the odor could be stronger near penetrations in the wall - especially penetrations near the bottom of the wall, since that is where mildew and mold normally start.

So I have two suggestions - one you already mentioned.

That would be destructing testing. It is usually easier to cut holes in interior walls than exterior walls for "exploratory surgery." Actually, a 600-volt cordless sawzall can cut through anything pretty easily. So I should say it's easier to patch holes in drywall than it is to patch holes in stucco or wood siding.

One option before the sawzall comes out would be an infrared (IR) camera inspection. I chuckle when I see ads that say, "We can see inside your walls." I have an IR camera, but I cannot see inside your walls. What you can see are anomalies inside a wall from very slight temperature differences. These differences can be from moisture entry, missing insulation, or even overheated electrical circuits or termite activity. With experience, a good thermographer can be pretty certain what caused these anomalies, but won't say what the cause is with absolute certainty. Missing insulation is very easy to see because it has a very "regular" shape. I can be 99 percent sure that an IR photo shows missing insulation, but the only way to be completely sure is to really look in the wall.

An IR inspection can usually tell you exactly where you need to cut holes for further investigation, saving the cost (and mess) of cutting unnecessary holes. It may also show you similar problems starting in other areas that are not significant enough to cause odor or visible damage.

Anyone out there have any other ideas on what could be causing this odor, or how to find out?

Randy West owns Professional Building Consultants in Prescott. He is state-certified and has performed more than 6,000 home inspections in the Prescott area. West serves on the Home Inspector Rules and Standards Committee for the Arizona Board of Technical Registration. Contact him at randy@inspect

prescott.com.