Wood movement - different thicknesses

[Aaron Liebling]

Asked this question buried in another thread and didn't get a reply, so thought I'd try again.

Does wood of different thicknesses move differently enough to be a problem?

If you have two shelves (same wood and grain direction) of significantly different thicknesses, would it be fine to attach them with fixed posts (i.e. no mechanism for movement)? If it's a problem, what kind of thickness differential is significant?

[Scott T Smith]

Irrespecctive of thickness, wood will move approximately the same amount based upon the milling pattern and % of moisture content change. So a quartersawn oak board 1/2" thick that experiences a 2% change in MC% will move the same amount in width as a 1" thick board.

What varies though is distortian. Thinner boards tend to distort more during changes in MC% than thicker boards.

[Aaron Liebling]

Thanks Scott, that fits with my thinking. Should be good for what I'm planning. I'll post photos when it's done so everyone can presage doom and tell me how it will fall apart in a few short years! :D