One of our offices is based in The Netherlands, and The Netherlands can be really chilly and uncomfortable. Wet and humid. And some Dutch clients think that their climate is not very suitable for a wooden house.
Let’s look at the facts. Below are four graphs, with the relative humidities in Utrecht (Netherlands), Ukmerge (Lithuania), and Moscow (Russia).
relative humidity Utrecht
Previously we wrote about types of wood (wet, dried, laminated) and the shrinking of log houses and how we deal with the shrinking. In this post we want to show a little more about the actual drying process, and cracks. Because drying and cracks are very much related.
Why Does Wood Crack?
The photo below shows a crack in a wooden disc. Why does wood crack like this? Very simple: drying.
cracked wooden disc
When wood dries, the drying process starts at the outside of the logs. While the humidity goes down from 15% to 12% near the outside of the log, more to the the center of the log the humidity initially remains at 15%. And that is a problem.
A wooden house will shrink. No matter how dry the wood was initially, over time, during a period of approximately two years, all residual humidity will slowly evaporate from the wood and the wood will become more dry. Wood shrinks in one direction only: lateral, but not longitudinal, or in other words, logs will become thinner, but not shorter.
How Much Will A Wooden House Shrink?
Because the logs of a wooden house shrink slightly (approximately 1% for laminated wood), we need to take special precautions. When mounting vertical battens to the log walls (to support insulation for instance) we need to make sure that the logs can slide, or shift. See the photo.