Q: I withdrew from a home purchasing contract because the inspector determined visible mold/mildew/fungus and structural damage on 40% of the home's joists/main girder. A few years ago, the homeowners disclosed structural damage from "white rot" and repairs were made. Now, evidence shows that the moisture problem is still there as well as further damaged wood.

I want the rotten wood removed. The engineer says mold problems are bogus and that the rotten wood will not contaminate other wood. He also said that mold/mildew/fungus will not need to be treated because, increased ventilation will improve the situation and kill the mold. He states that since mold causes no structural damage, there is no need to remove it. Because of this, I lose my deposit, have to pay for the engineer's report, the survey and the home appraisal. I'd like to prove him wrong. Any info or suggestions are greatly appreciated.

A: Wood decay is primary caused by two groups of fungi. Fungi that causes brown rot and fungi that causes white rot. White rot occurs when the component of wood that is brown (lignin) is digested and leaves the white portion of the wood (cellulose). The opposite is true for brown rot (the cellulose is digested). Wood decay is defined partially by the loss of structural integrity.

Wood decay, without question, can impact the structural integrity of the water damaged/mold contaminated wood. "Dry rot" (mold decay under wet conditions that later dries out) is, without question, a cause of structural failure. It is true that the mold will not contaminate other wood unless the environment is "conducive to growth," meaning the wood is chronically wet. Solid wood doesn't decay after a single exposure to water. If the improved ventilation prevents future moisture condensation, then additional "rot" should not occur. However the existing mold may not die but is likely to become dormant. Mold spores are often quite resistant to desiccation.

Removal is usually the best remediation process for wood that has had extensive wood decay. Surface mold remediation on structural timbers can be accomplished without removal if the wood decay is not impacting the structural integrity. The process usually includes cleaning the surface with a HEPA-filtered vacuum , sanding or blasting (dry ice, soda or sand), disinfecting and then encapsulating. Depending on the condition, it is often more cost-effective to replace the wood.

I have created a guideline that is based on data provided by Dr. Chin Yang of P&K Microbiology, Cherry Hill, N.J. He is one of the world's most experienced microbiologists. Click here for the guideline.

Thanks to Mark Goldman, who is a senior air quality scientist for Engineering and Fire Investigations (EFI), a firm that provides mold investigation and indoor air quality services nationwide. Mark can be reached at mark_goldman@efiglobal.com.

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