Freezing and Thawing and Lumber

[Stephen Tashiro]

Things such as masonry that contain moisture can be weakened by repeated freezing and thawing. The moisture content of lumber is a frequent topic of discussion, yet I've never heard any one warn that lumber might be damaged by repeated freezing and thawing. Is it simply too flexible to be damaged?

[Kenneth Moar]

Standing trees seem to survive winters no problem, mabye they stay warm
somehow, but I doubt it. So why would there be a problem with sawn lumber?
particularly if the MC is below the fiber saturation point( around 30% for many common species)http://www.sawmillcreek.org/images/icons/icon12.gif

[Richard M. Wolfe]

The moisture in living trees has a mixture of substances along with the water which acts as an antifreeze. When the tree is felled the balances are changed and the moisture can freeze if the tree is subjected to low enough temps. There is endless discussion among northern sawyers of the best blade and techniques to use for cutting frozen wood. The wood itself is not harmed because of the way the water is dispersed in the cellular structure. Freeze damage comes about by ice crystal formation and the resulting expansion. Ice crystals formed in frozen wood are very tiny and countless air 'pockets' in the cellular structure prevent damage. The succulent growth of leaves and structures of other non-woody plants has too much water to allow for this, hence the freeze damage seen in them.

[Stephen Tashiro]

I think the details of how the water is dispersed in the cellular structure of wood must be very interesting. Other parts of plants, for example fruits, are structurally damaged (at least from the point of view of eating them) when they are frozen and thawed. If the moisture is within the cell walls, then I don't understand why freezing wouldn't burst the cell. Maybe it does and maybe this doesn't matter? I think of plant cell walls as being rigid. Perhaps the walls of the cells of wood are flexible. I interpret your answer to mean that the moisture in dead wood is not in the cells themselves but on the outside of them, trapped between the fibers of wood. So the fibers have enough give to flex back an forth as the water freezes and thaws.