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Q:This is not about mold, but a very destructive fungus we have in new wood used to rebuild porches in an historical building. None of the old wood has been affected. For example, a 2 x 2-inch upright post, before it broke apart, appeared to have what resembled a clean saw cut all the way through. We have attempted to file a claim with our insurance company, hoping they would investigate lumber mills that supplied this wood, but they say it is from water damage, which it is not. The wood appears to have been sold to the carpenter with this fungus already active within the interior structures of the wood. What would you suggest?

A: Wood, when it is still alive, will not support the fungal growth described in your letter, due to the presence of naturally occurring chemicals (terpenes and others) that resist fungal growth. When a tree is cut down, those fungal-resistant chemicals remain and inhibit fungal growth unless the wood is exposed to chronic moisture. The wood you have described had to have been exposed to moisture for some time. This exposure may have been at the time of logging, prior to drying in a kiln, at a mill, in the lumberyard or within the hands of the installer. It is impossible to identify where or when the initial moisture source occurred based on the information available.

When the lumber was installed, the mold (nonreproductive fungal structures or mycelium) may have been established within the wood, but not producing the visible fruiting bodies as seen in the photographs you have provided. Although pre-existing mold growth was likely within the wood, the environmental conditions that the newly installed wood has been exposed to must have been conducive for the reproductive bodies to be generated. In summary, it is likely that the "new" wood wasn't very new and when installed it was probably exposed again to a moisture source. Replacement of the wood is the only recommendation for wood as badly damaged as seen in your e-mail.

The quality control, or lack thereof, is probably quite variable among lumber mills. The best source of protection is knowledge. Wood species like redwood or cedar are more expensive but are highly resistant to fungal growth. If possible, using these types of woods will avoid most fungal problems. Pressure-treated lumber is resistant to mold growth, but if contact with skin is likely, then you probably don't want to use it. A careful inspection of the wood upon delivery and prior to installation is another safeguard. Knowing the storage conditions of the wood since its milling and kiln drying could be important. The wood should never be in contact with soil and should be sealed immediately after installation.

You didn't state how long ago the installation occurred or what climate the wood has been exposed to since installation. Perhaps the carpenter could go to the lumberyard and show them the wood if it had been delivered recently? It is unlikely the identity of the lumber mill could be found, unless the wood was recently purchased and record keeping at the points of distribution was unusually good.

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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If you have a question for a mold expert, please send it to Brett Lyon, senior editor of construction.com at brett_lyon@mcgraw-hill.com.