I don't understand how a frame stays square when using green timbers. When considering shrinkage, I imagine the joints and beams shrink together at a relatively similar rate, so no problem there, but wouldn't that call for the entire structure to shrink? For example; Say you have a 10x8 timber frame shed made of green timbers all cut on the exact same day, even if all the timbers were to shrink at the same rate and, once completely dry, shrank to a loss of about 4 square feet - you're talking about joints that, if possible, pulled all that weight at an inward angle but somehow the foundational beams don't bow at an inward angle as well?
But if two adjacent posts are holding up a vertical post, and those posts connected to other vertical and horizontal posts, and they're all simultaneously shrinking - than wouldn't there still be such amount of shrink that would cause the house to "lean" into itself at causing beams to move out of square?
The Police You're WAY overestimating the shrink rates of wood... Here's a quick lesson: there are 3 types of shrink in wood: Radial, Tangential, and Longitudinal... Radial (if you were looking at the butt end of a beam/board) would be the shrinkage causing the rings to get closer together. Tangential would be shrinkage perpendicular to that... eg: if the ring lines were running left to right on the end, the shrink of Tangential would be along the top and bottom of the beam/board (and Radial would be the shrink along the right and left faces...) Those two types of shrinkage are the main amount of shrinkage that any wood goes through... that's why you see green beams develop cracks... However, Longitudinal shrinkage... well, Don was pretty much right. As far as length, a typical wood only shrinks a fraction of a percent... maybe 0.1, 0.2 or something... ...and THAT's the dimension that dictates the dimensions of the structure: LENGTH of the timbers. So, if you were to build a 10'x8' shed with green timber... with a typical 0.2% Longitudinal shrinkage, you would lose 0.24" on the 10' side, and 0.192" on the 8' side... So, instead of 80 sq ft, you would have about: (9.98' x 7.984') = 79.68 sq ft ; for a total loss of 0.32 sq ft. Not bad.... The last thing that you should know is that ALL woods have different shrink rates. There is no universal rate. That's why certain woods are better than others for framing... some have better properties over time... You basically want a wood with similar R/T shrink rates (there's a ratio for this, I forget the name...), and the lightest weight possible while remaining strong enough to bear loads without flexing too much or breaking... (Modulus of Elasticity/Modulus of Rupture)... That's why Douglas Fir is so popular... it's light, but still strong. Go to wood-database.com and you'll see all the ratings for every wood explained and listed. Hope this helped! Good luck with your shed.... :)
Tyler wood shrinks or swells between the growth rings not by much with the grain. the grain structure of wood is like many tiny straws banded together. the moisture is mostly contained within the tubes. This explanation is at its simplest mind you eg the cut of the lumber by its endgrain to a carpenter is very important.
