Mold on wood

Wes06 · August 01, 2018, 07:25:08 PM

I need some advice. I cut some lumber up early this spring an i wanna move into my shop. I know that my air flow wasnt good in the other shed its Only been air drying . Their is mold on some of it some yellow some white an some green on them. I was wondering what I sould do to take care of it before i move it into my shop .Any advice would be great thanks.

Brad_bb · August 01, 2018, 10:15:59 PM

You can use a bleach solution. Use 5% bleach maximum to 95 percent water. I've read studies that show 2% bleach works just as well as 5%. Any more than 5% bleach does not help you kill mold any better.

My first (and only experience with mold) was some spruce trees I peeled/de-barked in spring. I put them into a dark shed and they quickly grew mold.

The trick is air dry them outside where there is airflow until at least the surface has dried well enough. If you dry inside you need to have some airflow to prevent moist enough conditions for mold to grow. Currently I dry in my polebarn which does get some air exchange and is about 10 degrees hotter than outside in summer. I don't have mold issues. If your shed is sealed up well, you need to create some airflow. You also need a way for moisture to get out. If you open the door each day or every other that might be good enough. Monitor it.

For drying wood outside, you need to stack and sticker it well. you need a cover to keep the majority of rain off. You will get the sides wet from blowing rain. Just use corrugated sheetmetal on top with some weight on it to hold it down in a windstorm. I take a log and cut in half and put some 3.5x3.5 stickers on the sheetmetal and set the log halves on top. When drying inside I just stack some cants on top for weight.
Tip: It's taken me awhile to learn this, but try to cut your boards at standard lengths like 8' or 12' plus what ever you'll end up trimming off after drying(like 8'2" or 8'6"). Use pallets to stack and sticker your wood so the pallets can be easily moved with a forklift. Use hardwood 2x4's on 16" centers and use four 5/4 boards in the 6" wide range as the top decking. Use galvanized nails or coated screws. Pallets like this will allow you to stack lumber stacks on top of each other while making it easier to remove one particular stack when you want to.

YellowHammer · August 02, 2018, 11:57:07 PM

If the wood is ready to use, then nothing takes off mold faster than a planer. :D

PA_Walnut · August 03, 2018, 06:37:13 AM

Quote from: Brad_bb on August 01, 2018, 10:15:59 PMTip: It's taken me awhile to learn this, but try to cut your boards at standard lengths like 8' or 12' plus what ever you'll end up trimming off after drying(like 8'2" or 8'6"). Use pallets to stack and sticker your wood so the pallets can be easily moved with a forklift.

You didn't mention the species of wood? some will surface stain, and others just surface.

Tru'dat! x 10! i was cutting 6,8,10,11, 12,14, 16' (whatever the log yielded) Now its 8' only and 12's that are cut to 8' and 4' for stickering. (another YHammer wisdom...when he makes his millions, gonna see if i can get him as a consultant!) :D

Since i finally have plenty of stickers stocked up, going to 16" spacing for some testing.

GeneWengert-WoodDoc · August 03, 2018, 10:37:10 AM

Mold and mildew will grow on any species of wood; they can even grow on a plastic shower curtain in a bathroom shower. These fungi, like all common fungi, need warm temperatures (80 F) is ideal, water (wood must have surface moisture equivalent to 99% RH), oxygen, and food. They food they need is NOT wood, but is the dust, dirt, microorganisms, or sugars on the surface (sugars especially right under the bark). So, mold and mildew are only a surface phenomena; a tough brush will often remove the fungi (for example, 3-M Brushalon). However, if the conditions are good for mold and mildew fungi, we can expect that conditions are also suitable for the blue stain, sap stain fungi, which do go into the wood and use components inside the wood for food. It is also likely that the conditions for mold and mildew are suitable for chemical oxidation stains in wood, like sticker stain, brown stain, coffee stain, grey stain, etc.

So, rather than eliminating the mold or mildew with chemicals, address the high humidity conditions, or slow drying, that is causing the desirable environment for them...and for other fungi and stains.

PA_Walnut · August 04, 2018, 07:51:03 AM

Gene speaks truth!! My maple gets fans--BIG ones! Otherwise, it would be ruined in this hot/humid weather.

Wes06 · August 04, 2018, 08:55:12 AM

Ok thats what I will try. Ill brush the mold off before putting into my shop. thanks for the advice. The wood is red oak an cherry but seems the oak is worse then the cherry i haven't checked the moisture for awhile last time was 10% to 14%

Don P · August 04, 2018, 06:17:41 PM

If you're going to brush it... at that mc I'd do it with a light planer pass.

Brad_bb · August 04, 2018, 10:21:35 PM

Let's be clear, the mold is only growing right after it's sawn (first couple weeks in a drying stack), correct? Once the surface of the boards is dry enough, it should not grow mold.

I stack cherry, Walnut, Elm, and Ash(Ash is usually too dry to grow mold) and some oak, in my pole barn(gravel floor, tin walls and roof). I do not have fans. Must be enough air exchange, because I don't get any mold growth. Sometimes they dry in a stack in the main shop where they are cut for a few days before I move them to the Morton building.

If you put fans on your wood stack, especially oak, will it take too much moisture from the outside too quickly? Do you only use a fan in the summer humidity and not in the drier fall and winter?

YellowHammer · August 04, 2018, 10:59:46 PM

As Gene says, under the right conditions mold will grow on anything. However, cherry and walnut, and a few others are pretty much bulletproof, even when air drying in the summer in the south. I'm not sure you could mold them if you tried. Rack em, stack em, forget about them until they are dry.

However, there are some species that are very mold prone, pine is about the worst I've seen, and a young growth, sappy pine board can seemingly mold in hours in summer heat and humidity. In a few days, it can look like it's growing a beard (a little exaggeration, but pine will grow fur in the summer, I've done it.)

There are some species that are very sticker stain prone, most notably the entire class of "whitewoods" and will discolor in the summer heat and humidity before your eyes. Basswood, which we stickered today, will discolor as fast as a fresh apple slice. It's not due to mold, but the discoloration is caused by summer heat and humidity.

So sticker stain, which can really devalue wood, can be caused by both mold and enzymatic discoloratin, and will be most severe now, in summer. One solution to both problems is big fans and lots of airflow to speed drying and increase evaporative cooling which helps keep the wood cooler. Mold is usually skin deep and can easily be planed off, enzymatic stain will go well into the board, deeper than can be planed, sometimes.

Putting fans on red or white oak is sure death, as the properties of the wood dictate if it will work successfully. Fans are not necessary in the drier, cooler months, when it is too cool for mold to grow. However, in certain species of wood, enzymatic stain can happen very quickly if the temps and humidity rise, so I will generally run fans even in winter to accelerate drying and as an insurance policy.