Bustin' the Myth
17/03/09 09:38 Filed in: Technical
I am referring to the myth of that kiln dried logs and timbers are in fact completely dry.
I am referring to the myth of that kiln dried logs and timbers are in fact completely dry.
Most folks are unaware of the process of drying lumber or timber.
Lumber is cut from logs then piled in stickered piles and allowed to air dry for a short period of time.
This piled lumber is then placed in a kiln where the humidity and moisture is controlled for a period of time.
The wood is basically cooked while the humidity (moisture content) is slowly lowered.
The result is lumber that has been stabilized at a certain percentage of moisture content left in the wood.
This process eliminates checking (cracking) of the boards and future warping, as the cell structure of the wood is stable.
Logs and timbers are an entirely different story.
For instance, a kiln dried log or timber is measured for moisture content to a depth of one inch into the wood.
Timbers used for framing are typically 8” and up to 12” thick.
There is still a lot of moisture left in a timber that is 12% dry at one inch into the wood.
It would take weeks of kiln drying to get these timbers completely dried out.
Checking will still occur in kiln dried timber although perhaps not as much as green timbers.
Air dried timber is timber that has been stacked outside with a makeshift roof or tarp on top of the pile.
Air drying also stabilizes the wood but it may dry too fast in dry climates or too slow in wet climates.
The myth that kiln dried timber is better for timber framing is false, as the wood has a head start at drying in a controlled environment but it is not dry or stable to the core, as is the case with kiln dried lumber.
Our experience indicates that air dried timber if stored properly (out of the rain and protected from UV rays) stabilizes as well as kiln dried Timber.
Regardless of the drying method, wood will take on the moisture content of it’s surrounding environment.
See my next post on ‘Shape Shifting’ for the rest of the story.
Most folks are unaware of the process of drying lumber or timber.
Lumber is cut from logs then piled in stickered piles and allowed to air dry for a short period of time.
This piled lumber is then placed in a kiln where the humidity and moisture is controlled for a period of time.
The wood is basically cooked while the humidity (moisture content) is slowly lowered.
The result is lumber that has been stabilized at a certain percentage of moisture content left in the wood.
This process eliminates checking (cracking) of the boards and future warping, as the cell structure of the wood is stable.
Logs and timbers are an entirely different story.
For instance, a kiln dried log or timber is measured for moisture content to a depth of one inch into the wood.
Timbers used for framing are typically 8” and up to 12” thick.
There is still a lot of moisture left in a timber that is 12% dry at one inch into the wood.
It would take weeks of kiln drying to get these timbers completely dried out.
Checking will still occur in kiln dried timber although perhaps not as much as green timbers.
Air dried timber is timber that has been stacked outside with a makeshift roof or tarp on top of the pile.
Air drying also stabilizes the wood but it may dry too fast in dry climates or too slow in wet climates.
The myth that kiln dried timber is better for timber framing is false, as the wood has a head start at drying in a controlled environment but it is not dry or stable to the core, as is the case with kiln dried lumber.
Our experience indicates that air dried timber if stored properly (out of the rain and protected from UV rays) stabilizes as well as kiln dried Timber.
Regardless of the drying method, wood will take on the moisture content of it’s surrounding environment.
See my next post on ‘Shape Shifting’ for the rest of the story.