Remember that when wood is in its natural state, living and growing as a tree, it’s made up of lots of cells that contain moisture in the form of ‘free’ and ‘bound’ water (see previous blog).
When the tree is felled and dried for usage, it’s obviously forced to lose this moisture to some extent, in an effort to make it more suitable for modern living conditions within our homes. As it loses this moisture past its FSP level, it will shrink dimensionally but this shrinkage will vary across length and width.
The least dimensional change will be along the length of the timber (length being the direction of the grain) and can be as little as 0.1% during the drying process.
However, the dimensional change that should be of most interest to every wood floor owner is the change across its width (at 90 degrees to its grain direction) because this can be as high as 8-9%.
Can you imagine installing a floor that consists of 30 boards across its width, that are each 150mm in size, and every board is forced to shrink by just 2% due to poor or insufficient acclimatisation? What would happen? What's 2% of 150mm?
Every plank would shrink by 3mm that’s what…creating huge gaps between them and this will usually cause the owner to claim that the flooring is 'faulty', which it's not.
What about that same floor when the situation is reversed and the finished floor is forced to absorb moisture?
A 2% expansion would mean that every plank will expand by 3mm now, causing the floor to buckle and possibly even move structural walls as it expands outwards.
Every natural wood floor owner should be aware of this information to some extent, and at the very least know and understand that their timber flooring is hygroscopic, and will change dimensionally when its moisture content is forced to change.
Why risk this potential time-consuming and costly situation when you can buy a simple device called a Thermo-Hygrometer that will constantly update you with the temperature and humidity level of any room, arming you with enough information to prevent any damage from dimensional movement within your floor?
