In the march 1991 #65 issue of fine homebuilding, on page 50, a dovetailed lap joint for a beam over a post is shown. The building inspector in my area is telling me that this joint is not strong enough to support the beam and any load on it. He wants to see mechanical fasteners ( which would not look very good) or braces that won’t go with the design of the house either.
As far as I can figure this joint should be more than strong enough ….
Can anyone tell me anything one way or the other
carp
Replies
The way I see it, from the top of your Post, any load can transfer up at a 45 degree angle. What I sometimes see drawn, is long 1/2" lag bolts, going from top of beam, into top of post. I usually see decorative cut Iron plate used, instead of store bought T's. Personnelly, I do not agree with the concept of a lag bolt used in this scenario ie hold down/withdrawel- going into End grain of Post, most of the time Ponderosa Pine Post, in my local. If you go with the Lag bolts, Predrill those beams on the saw horses, and I'd order those Lags asap, if the inspector or whoever will accept your plan. Good luck in communication Jim J,,ps watch out for the lenght of your Dove tail joint.
Dovetails are fine for drawers. But no way would I believe they're strong enough for a beam connection.
I think your building inspector is right.
If you really want it with a dovetail, hire an engineer to give you an opinion on it.
When everything's coming your way, you're in the wrong lane.
OK, after reading Boss' comments, I had to dig out the FH issue. I've successfully used that detail on two buildings, but with a smaller tenon. One was tulip poplar, which I wouldn't use again, the other a mixture of red and white oak. No rebar pins.
The joint is incredibly rigid. The oak building is a 2½ story. The first building was inspected and had no problem for the inspector, but I'm not sure she really saw much after understanding that I'd used sliding (French) dovetails for the second floor joists.
Both these buildings are assembled with almost nothing but dovetails. There isn't a stronger wood joint. That's why it's common in furniture and wagon wheels. I also used dovetails to attach my diagonal braces. We're in a very windy location, mountaintop, and I wanted something I could depend on.
Arguing with an inspector, however, isn't anything I'd want to do. But if the only other choice is hardware, yuck. Good luck.
PAHS Designer/Builder- Bury it!