Hi R.W.,



Depends...???

There are a number of scarf joints and/or corbeling scenarios that may be possible either in a format from the Iberian Peninsula which has roots in the Spanish and Pueblo areas of this country, or some other vernacular form...like Japanese, which can deal with such a "thin" beam. It is going to be really challenging to suggest any valued assistance without seeing a model of the structure intended and photos of the beams.

4.5" is extremely narrow (too narrow?) for a major ridge beam...



Really can't without photos and more design info like...there are a dozen or so I can think of just off the top of my head but without more information (i.e. photos, blueprints, etc) I can't even begin to make a good offering...



"Generally," I would suggest a corbel supported scarf, which fits into the design parameters of many Pueblo architectural forms of the region...or something Asian.

So...this would include a larger corbel under the scarf, which in turn is supported by an appropriate sized post. It would also include a corbel generating from the adobe walls as well, supporting the end of you black walnut ridge beam...

Please note! This is a rough guide of basic needs, and not an approved nor engineered perspective. I could probably facilitate something with the material to fit within your described parameters but as I routinely do, I suggest getting help from a PE if you are unable to do the engineering yourself, or have enough experience as a Timberwright to understand your margins of safety in sizing beams and joint design.

Regards,

j