how fast does wood absorb moisture? relative humidity where i am is at
14 to 16%. My wood was dried to 8%; specie is meranti. weather is sometimes rainy.what factors affect wood to absorb and not to absorb moisture?
thanks,
NORY
As I understand it the wood will over a period of time come to the same moisture content as its environment.
So if your normal humidity is 14-16% the wood will absorb moisture until it is also 14-16%.
Obviously wood in direct contact with water will absorb more so timber in exterior jobs should be kept from direct ground contact.
NOT.. Many places have a humidity level of 90+%. The wood in the fences, homes do no have 90% moisture content.
NOT
Close, but what does ground contact have to do with direct contact with water?
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If the wood has a constant source of condensed moisture, read that as setting into apuddle of water it will eventually become water logged. Humidity has little effect by compairison. I live in Houston and the humidity level is consistantly above 80%. No lumber supplier in Houston that I know of stores their lumber in a low humidity environment. Over time the humidity level will cause some dimentional changes however the moisture content of the wood is not going to go back up to 80% here in Houston if kept out of the rain. As an example, when using new cedar pickets they are often still wet when I nail them up on a fence. A week to 10 days later the pickets shrink and dry out in this humid environment.
You understand it incorrectly. Over time, the moisture content in wood will reach an equilibrium with its environment; that is, the wood no longer absorbs moisture from the environment, nor does the environment absorb moisture from the wood. This is NOT the same as the moisture content being the same in each.
Not correct. Not even *close* to correct. If your normal humidity is 14-16%, then you live in the Atacama Desert -- and wood will have a moisture content close to zero. Conversely, at room temperature, wood will have a moisture content of 14-16% at humidity of approximately 75 to 80%.
Google < "moisture content" wood equilibrium > to learn about this.
"Direct contact with water" and "direct ground contact" are not the same.
Wood will reach an Equilibrium Moisture Content (EMC) based on the relative humidity (RH) of the air surrounding it. Tables for same and lots of reliable information at
For your information, at 100% RH, the EMC is around 30% moisture by weight for nearly all woods. It's called the Fiber Saturation Point (FSP). After that, it's called waterlogging, and requires liquid.
I found the comments about equilibrium enlightening; thanks to the posters who described the situation so clearly.
Ground contact, though, I gotta chime in. Ground contact often means dirt out in the rain. I made raised garden beds out of plain old 2x. They rotted out at the bottom. They got alternately wet and dry, wet and dry, and away they went. OTOH, your typical viking craft sunk in a lake somewhere, or some prehistoric Australian pine tree sunk in a bog, will become saturated with water, but won't rot. So, yes, wood immersed in liquid water will come into equilibrium, become saturated. No, that's not why we keep wood off the ground. One situation, equilibrium moisture content, is sorta kinda static. The other, ground contact, has to do with change. Rotting could happen in either case; greater than 25% moisture or alternating wet/dry.
And I don't know any of this stuff myself; I just got "Encyclopedia of Furniture Making" from interlibrary loan.
well woods are different some do it fast some are slow. but if your humidity is so low the wood is not going to change. it may shrink a bit at best. once wood is fully dry it does not absorb much moisture. I don't think I see much of an increase maybe 1% over the year or so. Knight-Toolworks
Oxygen is the determinant. The bacteria and fungi that do the deed are aerobic. Bottoms of bogs (sorry, blokes, I know what a bog is to you) and lakes are poorly oxygenated. Also often very acid and thus highly mineralized, another thing the decay bacteria don't like.
There are a bunch of logs that sank in the big lake north of here waiting to come to market after a hundred years. Trouble is, they make big holes when they're lifted.
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