Properties of green timber
1. Wood, as it dries, shrinks tangentially to the grain more so than along the length of the grain ( in fact shrinkage along the grain is so small as to be ignored ). In a round log this means that the outside rings of the log will shrink more than the inside rings ( as there is more cross grain on the outside ). This invariably leads to checking in the log. This is a natural occurrence and is not an indication of a faulty log. Checking will develop in every log home, in every log on every part of the log. Some checks will be facing up, some facing down, there is no way to predict where the checking will occur. If a log is left out on a hot sunny day, you can even hear the surface checking as it occurs, as a series of small pops and snaps.
 
2. A major check will occur along the length of the log. This check will always occur from the pith to the closest edge of the log. Check the end of any round log and you will see this occur with certainty. Sometimes the check will wrap around the log along the length of it, but this is only because the edge closest to the pith changes along the length of the log. Knowing this, the location of this check can actually be controlled - a groove cut into the wood towards the pith will artificially create the edge closest to the pith and therefore force the checking to be inside this groove. We'll see later how this can be used to advantage in log building.
 
3. As a green log dries it shrinks. Anywhere from 4-5% is the normal allowance. It will depend on the species of wood used and how 'dry' the logs you are using are( ie: how close your green logs are in moisture content from the equilibrium moisture content for your area ).
 
So, how we do take all these things into account in order to stack logs together and ensure they are tight from the day they are built until the process of drying completes in about 4-5 years?