Gramble style roofs

[kkcomp]

When build trusses for a Gramble or barn style roof do you put gussets on both sides or just one?

[Don P]

Gambrel designs are what you're looking for.
Without a structural guy in your back pocket, I'd stick to the details from one of these, being mindful of their spans, loads, etc.
Building Plans (ndsu.edu)

My small "barn"/shop is 24'wide. I tied across the pitch break up top with ~16' 2x6's nailed in the plywood gusset triangle. Basically triangles sitting on sloped walls instead of trying to maintain a tall open arch which I didn't need.  

The short answer is, yes, both sides, more nails NOT screws, than you would imagine.

[kkcomp]

Thanks Don P always good info to share.  I do my layouts at Blocklayer.com lots of great calculators and designers on that site. I asked because on the shed I am building as practice for the real barn had one of the trusses twist before I could lay down the decking. I was just wondering if gussets on both sides would have prevented that.

[Don P]

Yes, there is usually a nail pattern for the gussets on the front and back that spaces the nails best, mainly you don't want them stacking up splitting things but the joints need a lot of connection strength. Twisting is a bracing problem too, throw more braces, especially as things get bigger.  Often I'll brace inside so i can leave them till I'm done, or, there's still one up in my barn I never took down.

I think blocklayer is giving dimensions but not connection forces/strengths needed.

[kkcomp]

Correct but dimensions is a good place to start and I figured a shed would be good practice before I started on the real stuff.

[Tom King]

The main thing I don't like about Gambrel roofs is doing the slope change when putting the roof on.  I've never seen one that I thought really looked good.

I put a standing seam roof on a house with intersecting Gambrels, a low slope roof between the meeting Gambrels, dormers, and 10 skylights that we folded the metal up to form the curbs.

This was the modern snap together standing seam, with transition pieces.  

It was only a few hundred yards from our house, and for a really nice guy with deep pockets, or otherwise I wouldn't have even talked about it.  He could never get anyone to put asphalt shingles on it that didn't leak, and I don't do asphalt shingles.

After we finished the house, he wanted me to do the boathouse too, and build a cupola for it.  The boathouse already had the louvered base for a cupola on it made out of Mahogany, but a hurricane had blown the top off.



 

[Sod saw]

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In reply #1, Don stated that nails should be used and not screws.

My question:    Why?


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[doc henderson]

Have you ever broken a screw?  Have you ever broken a nail?  Screws do not pull out easy but can break with shearing forces.  (sideways).  Nails can pull out but bend rather than shear.  In search and rescue, there are manuals that talk about proper number and spacing of nails for makeshift shoring and bracing.  I also like staples as they hold well and are less likely to shear off more like a nail.  I also use glue to increase the surface area holding the truss components.  I made a really cute and functional 8 x 12 shed for the chickens in Hays.  I did my shop with a second story.  I cheated in that I did a I beam wood trussed floor and cantilever 2 feet over the support wall.  I then put a straight second floor wall over this, but it had 3 six floor openings with header, and this became a dormer.  It made a 2 foot by 6 foot step out to the edge of the floor.  I put a traditional truss on that wall to the other side.  I grouped several trussed and divided the roof into thirds and then made gussets that also had a pocket to hold beams that supported the roof.  I then laid "rafters" from the outside of the floor to the edge of the trass that made the gambrel shape between the 3 dormers along the side of the building.  Hard to explain but more of a foe gambrel, but easy for one guy to build.  then did a shed off the floor rim joist and got all kinds of space.  I will see if I can find a pic.  this all tied two existing buildings together.  we then built a 3 story 8-sided tower with a "lookout" with windows all around.  It looked like and old barn with a silo and milking shed.  for whatever that is all worth.  

[Don P]

That's it, unrated screws snap unpredictably. You want ductile failure rather than brittle failure. The nail is very ductile, it will bend but still hold. I use screws to assemble often and nails to hold. There are structural rated screws. If the application is structural, there's the screw for the job.

IMO a gambrel looks good as a decorative element on the ends of a taller building that has long shed roofs projecting off the upper pitch. Essentially full length shed dormers. Gambrels suffer the same problems as A frames as far as living in one. You don't get full use of the footprint and lighting them in a pleasing way is not easy.