Sunday, November 06, 2005

Some Black Mold is a Harmless Stain That Came With Your Framing Lumber

Don't mistake this harmless black mold for "toxic mold contamination" on wood framing in your building. It's a cinch to determine that it was there at the time of construction. It's probably Ceratocystis/Ophistoma.

One of my clients in the Northeast saw "black mold" on floor joists overhead in his basement ceiling. He launched a $600,000. cleanup campaign with his insurance company, lawyers, investigators, the works.

In this case, even a cursory inspection by an investigator who was familiar with this particular mold could have disclosed that the "black mold" that frightened the owner was of really no concern other than as a cosmetic issue.

Cosmetic-only mold, or "bluestain" is often found on framing lumber. Two famlies, Ceratocystis sp. and Ophistoma sp. produce black surface molds on lumber that has been left wet, usually from being stored outdoors. (So much for "kiln dried" lumber your builder paid extra for.) There are [with only obscure exceptions] no health hazards reported from exposure to these molds, and they are not wood rotters. This is a cosmetic problem.

Few experts would be so bold as to assert that they could identify a surface mold without microscopic examination. This group is a reasonable exception.

See the black mold on this wood beam? It's only on one of three 2x12s. This mold was on this 2x12 at the time of construction, it's not growing in the house.

Look at the sudden stop that the "black mold" makes on this plwyood roof sheathing where the (black moldy) edge of this rafter meets the roof sheathing !

Sure the attractiveness of a growth surface to individual mold species varies by what that surface is made-of, and a rafter is not chemically identical to the plywood roof sheathing. But they're both cellulose. Mold growing on a wood structure would not be expected to make such a sudden stop at the plywood if it had in fact been actively growing in this location after the house was built.

For another clear phenomenon of un-natural edges in a mold growth pattern look at the end of this cut end of a rafter. If attic conditions were producing mold growth, it would not have stopped so cleanly at the cut surface.

These clues are compelling evidence that this particular mold was on the lumber at the time of construction.

More in-depth review of what mold looks like and stuff that is not mold can be read at

This Blog is About: What to do about mold in buildings

When is mold a problem in buildings? What should be done about it? Find expert field and lab testing, inspection, remediation advice, but ... avoid "fear of mold" and bogus advice which can both cost you and yet may not really address the problem effectively. My interest is in providing expert service to my clients, protecting not only their health but their wallets. I provide field investigations to find problems and to recommend solutions to mold in buildings, and I operate a forensic laboratory in New York which accepts mold and other indoor air and particle samples for examination. In depth information is at and the links at that page. Website content suggestions are most welcome.

Case Histories: Here I post summaries of field and lab toxic or allergenic mold and other indoor air quality investigations. I omit private information. I describe observations, procedures, and findings helpful to readers who are trying to remedy their own mold, allergenic, carbon monoxide, odor, or other indoor air and related health concerns in their indoor environment.

Daniel Friedman