Hi Randy
I've been watching this with some interest to see what specific recommendations the veteran members have.
Having done that I'll take a few shots from the hip
Regarding the epoxy I have listened to similar debates among shipwrights, the debate is that you either entirely encapsulate the wood or leave a side to "breath". I have listened to the debate but have never seen any empirical evidence esp. on the let it breath side.
Another material used by shipwrights is "bedding compound" think caulking in a pail; this is spread liberally in the joint before assembly the purpose being to fill all voids and deny water from the joint altogether. Obviously a static structure is not subjected to the same conditions that a boat is but it may be worth a visit to the local boatyard. Or at least this is sufficient excuse for Steve and Gordon to pay you to drool over pretty boats (tell them I said so)
(Warning: exposure to other obsessive wood freaks may be hazardous to your financial health)
Now from a longtime Northwest house carpenters/remodelers perspective...that would be me
Two pieces of wood joined tightly together and exposed to the weather WILL ROT. Water that gets between two closely mated surfaces will be held by surface tension, will raise the moisture level of the wood at the juncture and provide a home for our friend brown rot fungus.
Obviously you cannot build joinery that is so loose as to let water drain freely so I think you have to do your best to deny the water entry in the first place.
What I was taught regarding exterior details was to make the thing work mechanically as best you can and then supplement with caulking.
Detail so that you leave no exposed horizontal (flat, level) surface or one that drains toward the building.
Make drip cuts on the underside of exposed members.
Make drip cuts or a hollow at post bottoms and elevate if possible.
Caulk the tops and exposed sides but never the bottom.
And a few words on caulking...
Always use the best you can. I usually use a Sikkens or 3M marine product.
Allow space for a volume of caulking that can expand with the material. A thicker bead expands less as a percentage of its volume as the wood moves and so holds up longer.
All caulking fails. Better caulking takes longer to fail.
Have fun..
J.E.B.
