Plywood and dimensional lumber gambrel trusses?

IHDiesel73L · Dec 30, 2021

I've seen these types of gambrel trusses discussed from time to time with various opinions of how well they work and how strong they are or can be if built in a certain way. The first time I had ever encountered them was in a factory built shed that my dad purchased years ago. It's 14'W x 18'L with 6' side walls framed 24" OC and has 24" OC trusses made from 2x4s and plywood gussets which are stapled. Its probably close to 30 years old at this point and has seen 2-3' of heavy wet snow sitting on the roof a few times in its life (located in New Jersey-ground snow load for the area is 30lbs/psf) and the trusses have not sagged and the walls have not bowed. When the shed was purchased there was nothing tying the trusses together at the bottom and aside from a small (4' or so) loft that my dad put in himself at the back end there still isn't. I'm considering a slightly larger (16'W x 20'L) to use as a sort of guest cabin/office on my property but the construction would be identical. This company ( Amish Made Classic Large Gambrel Barn Panelized Kit ) sells them in panelized kits which are reasonably priced and according to their website the structure is rated for 120MPH wind load and they will supply any necessary documents for permitting in your state. Presumably somewhere, some how, some engineer has run the calculations on all of this and blessed it with a raised seal. I haven't been able to confirm the finer details as they are closed until Tuesday. I figure I could either purchase the panelized kit or just build it myself as the photos on the website and the dimensions are all that would be needed in order to duplicate the construction. For good measure I would probably use 2x6s rather than 2x4s and high quality (no voids, etc...) 3/4" plywood for the gussets along with glue. I'm interested to hear what others think of this construction method. I will also follow up with whatever I hear regarding engineering documents, etc...after the 1st of the year.

s219 · Dec 30, 2021

When I was in high school and college, one of my summer jobs was working in a construction business that made pre-fab sheds. I probably built a few hundred of them overall, and quite a few had the gambrel roof. Early on we used 2x4 lumber and plywood gussets (held on with construction adhesive and staples). A couple years later we got a machine that would press in nailer plates (same used for most truss construction nowadays). I liked the plywood gussets better, feel like it was more thorough. OSB would also be suitable and has very good shear strength with staples and adhesive.

GLyford · Dec 31, 2021

There's a bunch of state university sites for ag extension service that have barn plans, usally all the same ones.
This is one such site:

Construction Building Plans

www.ndsu.edu

I haven't been poking through the plans lately but I seem to recall there being several gambrel truss plans in there, there may be one similar to what you are trying to do. Also several types of pole barns. But a bunch of them are also older, so may not meet the latest codes in all areas.

m1garand762 · Dec 31, 2021

I made my own gambrel trusses for my barn. There is a website which I believe is www.blocklayer.com that has the engineering done for you. Input your dimensions and it tells you the exact length and angle to make every piece. I used 1/2 plywood gussets on both sides with carriage bolts for fasteners. My barn is 40 ft wide and 60 ft long we get a lot of snow and I have never had a problem spaced on 24s we made them from 2x6s. Obviously on your gable only gusset 1 side. It cost me less than 1/2 the cost per truss than the local truss manufacturer wanted