Sloping Roof Deck - Tilt Beams? 2

[maineeng]

Hello,

On a flat roof, with slope 1/4" per foot or less, if the roof deck flutes are parallel to the span, and the supporting beams are perpendicular to this, is it customary to install the beams plumb, or slightly out of plumb so that the slope of the beam top flange matches the roof deck slope? What is the slope limit when supporting beams must be installed out of plumb to match the slope and the slope can no longer be neglected?

 

[jayrod12]

Beams are always installed plumb.

Can you post a sketch of your situation just so there isn't confusion. Most of the time any beams running parallel to the flutes are separated from the deck via joist seats.

 

[BAretired]

On a sloping roof with beams spanning down the slope, purlins may be seated on the top flange of the beam. In that case, the beam webs would be plumb but the purlin webs could slope to match the slope of the beam. In some cases, sag rods are added to hold the purlins in line. Alternatively, purlins may be installed plumb with sloping plates added for deck support.



BA

 

[KootK]

is it customary to install the beams plumb, or slightly out of plumb so that the slope of the beam top flange matches the roof deck slope?

If it's the situation that I'm thinking of, I'll usually rotate the beams.

What is the slope limit when supporting beams must be installed out of plumb to match the slope and the slope can no longer be neglected?

Not much. 1:24 on a required 1.5" bearing surface or 1/16" max. See the attached document from SDI.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BSVBD]

Please post a sketch. Without a sketch, there is too must guesswork for us to logically assist.

Metal roof deck flutes must be parallel to the supporting element, whether the supporting element is a purlin, open-web-steel-joist or a beam, and thus, the supporting element must be perpendicular.

What are the supporting elements? If it's just a beam, the adjacent support cannot be very far from it. If it IS just a beam, you may need to shop weld a 1/4:12 sheet stock or install a sloping fire-resistant wood element, all depending on your construction type, code rules, etc...

There are too many unknowns. A sketch would be nice.

 

[msquared48]

Any ridge beam can be flat, but the purlins can slope from the ridge, and the sub purlins can be flat to allow the deck to attach.

Mike McCann, PE, SE (WA)

 

[hokie66]

Where I am, it is April 1, so I will assume you guys are just early. Silly thread of the week.