The hammer beam truss is more complex than other truss types. It is a beautiful truss, however, and also has the advantage of using shorter pieces of wood. The truss is composed of the hammer beams (red), hammer posts (blue) and hammer braces (green).
In this example, a through-tenon connects the hammer beam to the hammer post. A clever notch in the hammer beam makes for an extremely strong connection to the rafter. And all the other traditional mortise and tenon joinery is secured with hardwood pegs.
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In a high snow load area this is a hard one to pencil from an engineering standpoint. The load on the truss from the brace gets quite large. They look great but just aren’t efficient structurally. As much as a like them I wince when I see them on a new project.
I agree it is a tricky truss, about 90% of the time I see a steel rod used to hold everything together.
I’ve been hashing how to pull off hammerbeam trusses for a 35 foot span with a 12:12 pitch roof. To further exasperate the problem, I won’t have the ability to have large posts for their foundation. (ICF walls with a 6″ core) Oh, and did I mention a pretty significant snow load area? 😀
But after a lot of nights of laying in bed thinking about it while trying to get to sleep, I think I figured out a way. That way would be a structural ridge beam and free-spanned large rafters, mascarading as a hammerbeam truss, with all the beams, posts, and braces added to it. The house plan is square, so it’s also 35 feet for the perpendicular direction. The front half open, the back half having a second floor, so much easier to do different truss work there. So the ridge beam in the front will be spanning around 17′-6″,and I’m thinking dividing the space into thirds, meaning two of these psuedo hammerbeam trusses in that freespan of the ridge beam. I’m no engineer, but this sounds very doable.
Send an image of the design if you would like, that is quite a span. Have you thought about using a steel rod?
Brice
I’ll work up a .dwg drawing. I’d be curious of your thoughts.
hi,
do you have a hammer beam detail drawing with a shallower roof pitch? like 9:12 or so?
Not currently, sorry will put it on the list.
I have recently built a 40’x60’x16 shop for a friend,we used an engineered trusses for the building and they were 2×6 top and bottom cords with 2×4 webbing. Would it be possible to spanned 40′, building the same truss out of 6×6? Having them 4′ on center? 8′ would be great but …
You could do it our of 6x material but you would need to use some deeper timbers than 6x. Consulting a heavy timber engineer would be vital in determining everything works structurally.