Hi Hemlock,

Offsets are design, region and vernacular specific to the style of timber frame it is found in...

"Rules of 3rds" is more found in the finer member sizes of furniture...not in Timber frames as Jim stated.

In larger timber work, it is a "rule of quarters" but this is a very loose rule and more to do with structural dynamics within the joint intersection complex of a given union...

I work in mostly Eastern European, Middle Eastern and Asian modalities of timber framing. As such, I use ancient Line ruling methods and standards that tend to be more centralized on a timber (but not always center)...I also tend to use splines much more often and these can be of stronger more robust species...so dimension is often diminutive compared to American and Western European standards...

1" tenon thickness is not rare, nor are offsets and other anomalies compared to the standard American timber frames. We don't use oblique bracing, nor pegs very often...just gravity, and wedge joinery for the most part...

As you get deeper into the craft you will note the vast nature and stylizations within it...

Regards,

j