Steel Bar Joists on New Workshop - Roof ?

[kochevnik]

So I want to put a mostly flat metal roof on an open-ended shipping container shop - steel bar joists as the main support members for the roof between the containers.

Metal decking of course, but that wont work in this case because I want to collect the rain off the roof (this will be in eastern WA western ID) and the decking has to go perpendicular to the joists.

The joists will be on 4' centers and overspec'd like crazy for the load. No building code there so I want to super over engineer this to be safe.

So standard metal roofing is good, because it can go parallel to the joists with an underlayment ? But what kind of underlayment ? OSB ? How thick ? And how to connect that to the joists and how best to protect this from the weather. I dont want to have to replace this in 10 years.

How best to do this ?

 

[kbs2244]

By joists I assume you mean rafters.
Rafters are the sloping ones.
Joist are the horizontal ones that go wall to wall.

With that out of the way…

You will also need purlins to join your rafters.
If you keep the upper edge of the purlins the same as the upper edge of the rafters you will be creating a box like support system for your roof panels.

That may allow you to upgrade the thickness of the roof panels to the point you do not need any underlayment.

You will have to do the math to see if this makes dollar sense.

If you do go without underlayment I would think about turnbuckle type “X” braces on the underside to provide an anti-racking system.

 

[rustyjames]

So I want to put a mostly flat metal roof on an open-ended shipping container shop - steel bar joists as the main support members for the roof between the containers.

Metal decking of course, but that wont work in this case because I want to collect the rain off the roof (this will be in eastern WA western ID) and the decking has to go perpendicular to the joists.

The joists will be on 4' centers and overspec'd like crazy for the load. No building code there so I want to super over engineer this to be safe.

So standard metal roofing is good, because it can go parallel to the joists with an underlayment ? But what kind of underlayment ? OSB ? How thick ? And how to connect that to the joists and how best to protect this from the weather. I dont want to have to replace this in 10 years.

How best to do this ?

If you're planning 4' joist spans you're going to need something like metal decking, not OSB or plywood.

 

[Riverside]

Do you have the containers already? If not, you may want to compare the cost of putting up an enclosed carport-type building (tube frame with metal siding). I assume that cost is a big consideration, or you probably wouldn't be thinking of using containers. With a pre-engineered building, you won't have to figure out dozens of connection details. To collect rainwater, just add gutters and run the downspout into a barrel.

 

[Jeff Ivers]

So I want to put a mostly flat metal roof on an open-ended shipping container shop - steel bar joists as the main support members for the roof between the containers.

Metal decking of course, but that wont work in this case because I want to collect the rain off the roof (this will be in eastern WA western ID) and the decking has to go perpendicular to the joists.

The joists will be on 4' centers and overspec'd like crazy for the load. No building code there so I want to super over engineer this to be safe.

So standard metal roofing is good, because it can go parallel to the joists with an underlayment ? But what kind of underlayment ? OSB ? How thick ? And how to connect that to the joists and how best to protect this from the weather. I dont want to have to replace this in 10 years.

How best to do this ?

If by metal decking you are refering to the material to cover the roof, are you considering corrugated barn tin? If so, around here pole bars are built by installing trusses every four feet and then running furring strips perpendicular to the trusses at 4 foot intervals. The barn tin is then run in the same direction as the trusses, but supported by the furring strips. Size of furring strips is dependent upon calculated load and slope of finished roof. If the shipping containers are flat, you might want to span the entier width of the containers and center area to control your water runoff. A sketch, picture and dimensions would help with useful responses.