I’ll never be mistaken for either Jamie Hyneman or Adam Savage of the Discovery Channel’s popular and long running series MythBusters, however I can occasionally do some debunking of urban (and rural) legends.
I do have to admit, watching MythBusters can become addicting – especially when it can be tuned in on Netflix and watched commercial free episode after episode!
Getting onto some sort of relevant topic…..
As a popular legend has it – sawn lumber grows stronger with age, supposedly even more so as it approaches its one hundredth anniversary of being milled from a log.
How could this aged lumber legend have begun?
Well, it may be more than just a legend. Old wood can, in fact, be significantly stronger than on the day it was first milled.
Huh? How could this happen?
It is not like the tree is going to grow any more – it is now a board, joist, plank or timber!
Because wood does gain strength as it loses moisture content. At around 12 percent moisture content, it might be as much as 50% stronger than as rough-cut green lumber!
Read more about green lumber vs. dry lumber here: https://www.hansenpolebuildings.com/2011/09/499green-lumber-vs-dry-lumber/
Aged lumber, unlike fine wine or whiskey, generally does not get better with age. As a rule, the mechanical (strength) properties of wood show little change over time.
Typically, age works against lumber the same way it works against our bodies – I know I am realistically not near as spry at 57 as I was in my 20’s!
Other than a reduction in moisture content, everything else works to weaken wood. Over decades there is more than a passing chance the lumber has been exposed to evil stuff which can significantly weaken structural wood.
This would include nasty insects, fungi (not “fun guy” like me), being excessively loaded (too much weight on it) or elevated temperatures (think of roof framing on the south side of buildings).
Want to go further? Test the strength of a sample of rough-cut green lumber for strength properties today, come back in a hundred years or so and retest. I’ll watch for your results!