Mold on wood beams: a woodworker is renovating an old industrial building. He’s getting mold on the wood beams and, since the environment is pretty normal in terms of humidity and temperature, he wants to know why the wood is getting moldy so fast.
Ian Kirby: There is insufficient description of the mold to identify whether it’s a fungus that would cause decay or simply a stain on the beam. The problem may be a carryover since it’s a renovation if the place had been closed and unheated for a long period, then the fungal infection may have developed at that time. Find someone locally who can identify the fungus. But take it seriously. Suppose it’s dry rot (serpula lacrymans)? Left alone, it will eventually affect the load bearing strength of the beam.
In the meantime, try this simple field test. Using a probe your Swiss Army marking knife check the soundness of the wood by sticking the point of the blade into the beam. If the knife goes in, even part way, with little or no resistance, you have a problem. Get help. If the wood is solid enough, then a thorough drying, with warm blown air, should solve the problem. If it doesn’t, it’s time to go back and get help.