I-Beam Size?

[harleyhouser]

I have just got threw building my 40'x60' shop with 12' walls. It has 8" I-beams on the end trusses and 12" I-beams on the two center trusses. My question is that I want to put a lean to across the front of my shop 20'x60'. But I would like to be able to have a beam span the entire 60' so I don't have the two supports in the center. I hope I am explaining this well enough I can draw a picture and take a picture of it if needed. The end supports that hold each end of the 60' beam I have not decided on yet but that part should be no big deal. The 60' beam will have to hold up one end of 1200 sq. ft. of perlins and sheet metal.

 

[Charles (in GA)]

The beam would be so large as to not be practical.

4 posts, one on each end and two equally spaced in the middle, 20 ft gap to span with a C channel.

A straight 20 ft I beam would have a fair amount of sag in it, would have to be between 12 to 18 inches tall (WAG), and would be crazy expensive.

Charles

 

[Architorture]

the roof load won't be your biggest problem...in order to have a beam be sufficiently stiff over such a long span it has to be quite deep just to support its own weight. as stated about it simply isn't practical and the beam would be extremely expensive. there is good reason that most cheap big box stores are built on something like a 30x30 grid

 

[AndyA]

As a reference, one of the buildings I frequent has roughly 1600 sqft roof with a 38ft free span on one side. It uses a 24" "I-beam" for that span. I don't know then weight per foot, but it's THICK! A quick google and the lightest 24" I-beam I found is 55 lbs per foot. 55lbs x 38 ft x $0.50/ft = $1045.

Yeah, you want poles!

 

[Sureshot]

I think you need to check with a truss builder or engineer. I have a beam across my 42x60 with a 4k crane on it and I think it is 14" with a channel cap. Big box stores and other public places are built to an extreme spec because of public access. Op doesn't give location either. 60' is a lot but you may get 30'.

 

[Charles (in GA)]

Best to use a bar joist, since the loads are fairly light. Still, the joist would be fairly tall, so it would have to be quite high to make it work.

Charles

 

[harleyhouser]

Thanks for all the replies, I never thought about contacting a crain company as far what they use. Also I am going to look in to a bar joist system. As far as the cost goes, I'm more concerned about making the free span than I am the cost. The benefit I would receive would far outweigh the cost. Someone asked about location, I live out in the country in Oklahoma.

 

[Sureshot]

I found our local truss builder the best source of info. They deal with roof/floor loads and beams all the time

 

[Architorture]

the general rule of thumb for roof steel design is L/24 to approximate the depth... so a 60' span is a minimum of 30" deep and weigh 100plf plus. it just isn't a very efficient use of steel