I have some air dried pine that I would like to use for framing a porch around my house. The MC is 11 to 20%. There is mold that has been growing on the lumber since we cut it and I did nothing to prevent the mold growth. As we are framing the porch roof it looks as if this mold is dying. Is there any harm in just leaving the mold on the lumber and closing it up? Should I spray with bleach to kill the mold?
(Sawing and Drying Forum)
From contributor A:
All wood has mold spores on it. If the moisture gets above 30% it will start to mold. If you spray bleach on it and let it dry it will be clean looking but by the time the bleach dried there will be mold spores on the wood again waiting for it to get wet again. Since the wood is dry and it will remain dry and be covered I would not worry about it. If it will be seen I would bleach it for appearance more than anything. Too strong a bleach solution is as bad as damage caused by the mold.
Do you want to use some chemical on the wood that will last forever? If not, then you can use bleach to clean the wood and this, especially on pine, will keep the wood free of fungal mold unless it gets really wet afterwards. Do you expect the wood framing to get wet? If so, then mold is not the issue, but decay. You should use pressure treated pine for wet locations. If it will not be wet, then eliminate the present mold and build. You can remove the mold with power washing. Mold is only on the surface as there is no food inside the wood. Rough lumber, when planed, eliminates to mold.
Why eliminate the mold on dry wood? I suspect that someone is concerned that the spores will be released. Active mold can also generate some odors that are not pleasurable. But if the wood will be dry, there are not too many issues that I can imagine. Incidentally, pressure treated wood does not prevent mold growth, as the chemical does not poison the food for mold. So, why put something on wood to control mold that will not control mold? There is a lot of wood with mold on it used for construction today. Overall, Contributor E’s response is the best, except that the final coating is not necessary or helpful.