Slope roof perpendicular to joist span
Slope roof perpendicular to joist span
(OP)
Hi,
We are designing a big box store with outdoor storage. The prototype drawings show the joists spanning perpendicular to the roof slope so that the roof deck ribs can be used for drainage to a gutter. The project manager wants to increase the slope of the roof, I'm suggesting 1/2" per ft. How do you specify joist seats for this condition? As the slope of the support beams increase, the joists will go out of plumb. For 1/4" per foot, should there be a special joist seat?
I have the Vulcraft manual and Vulcraft's "Designing with Steel Joist, Joist Girders and Steel Deck". They address sloping joists parallel to the axis, but not sloping the joist support.
Thank you!
We are designing a big box store with outdoor storage. The prototype drawings show the joists spanning perpendicular to the roof slope so that the roof deck ribs can be used for drainage to a gutter. The project manager wants to increase the slope of the roof, I'm suggesting 1/2" per ft. How do you specify joist seats for this condition? As the slope of the support beams increase, the joists will go out of plumb. For 1/4" per foot, should there be a special joist seat?
I have the Vulcraft manual and Vulcraft's "Designing with Steel Joist, Joist Girders and Steel Deck". They address sloping joists parallel to the axis, but not sloping the joist support.
Thank you!






RE: Slope roof perpendicular to joist span
RE: Slope roof perpendicular to joist span
However, I would check with a local joist manufacturer and see what sort of tilt the joists can tolerate. You can use standard SJI bridging (horizontal) except near the ends use X bridging to help the joists remain tied together laterally and not be affected by the slope.
The 1/2" in 1 foot doesn't sound like it would be an issue with the joists....and much cheaper than having the joist manufacturer custom make side-sloping seats.
RE: Slope roof perpendicular to joist span
RE: Slope roof perpendicular to joist span
RE: Slope roof perpendicular to joist span
Say you did have joists spanning perpendicular to the roof slope... my questions:
1. On your drawings, do you all give the joist bearing elevation for each joist?
2. How do you account for the roof slope with the bearing being consistent (top of a cmu coursing)?
RE: Slope roof perpendicular to joist span
2. If we were bearing on CMU, I think I would call out each joist bearing and space them at an interval that gives a good number, i.e. for 1/4" per foot space at 6' for 1.5" drop at each bearing point. Then would have to accomodate the slope at the seat or at the deck bearing. Still not sure about that.
RE: Slope roof perpendicular to joist span