I’m building a new garage. The structure will be 35′ wide x 25′ deep. The second floor over the garage will be a master bedroom and bath. To avoid posts in the middle of the garage, I want a second story floor system that can span the space without interior posts. My plan is to run the second story floor joists the long way (the 35′ direction) using standard 2×10″ southern pine. I plan to use two beams running the 25′ direction dividing the 35′ space into a 12′ span, an 11′ span and another 12′ span. The beams will run between garage doors so headrom is not a big concern. The roof load is carried on the front and rear walls above the footings, so the beams are only to support the flooring system.
A few questions:
1) Do I need a steel i-beam to span the 25′ or are there other options?
2) Assuming steel, what beam is required? What spec?
3) What support is needed under each end? Steel post? What size?
4) What is an approximate cost for the beams and posts? Where do you buy these?
5) Do you see any other floor system options (better and/or cheaper) other than the beams?
Thanks for your help!
Replies
You need to go to the library and read some structural textbooks.
A good to start is 'elements of strength of materials', by timesenko and young.
Internet answers, FWIAAW
A few questions:
1) Do I need a steel i-beam to span the 25' or are there other options?
Yes, there are mayn options, a built up beam first comes to mind
2) Assuming steel, what beam is required? What spec?
ASTM64, W12H26 (yeah, i actually did calculate that for ya, that will be a $62 eng charge <G>
3) What support is needed under each end? Steel post? What size?
DO NOT FORGET to correctly size the footing. A six foot square, 2 ft thick concrete pad should work nicely.
4) What is an approximate cost for the beams and posts? Where do you buy these?
Scrap steel is about 70 cents per pound, you buy them at the local scrap yard. You may need to weld together smaller lengths to get what you need at a scrap yard. A 25 ft W12H26 may cost about $500
5) Do you see any other floor system options (better and/or cheaper) other than the beams?
Build 2 walls in the garage
I almost never say this, but if you are not willing to research some textbooks at the library, hire an enjunear <G>
Garage Beam
It is impossible to answer your questions with the required accuracy on a site like this. There are too many variables and unknowns. My liability and your safety is on the line.
Yes, you can build what you are proposing using all wood / lumber construction. You should go to a lumber yard (not big box stores) where many have engineering and design assistance.
Junkhound is a smart guy, but does not have much patience with we mere mortals. :>)
When I had an engineer spec a beam for a 25' span with 12' 2x8 joists on each side, he came up with a 8" 34 pound beam and it was not big enough. The floor was still springy. It was not going to fall down but you could feel it flex. If I had it to do again I would use floor trusses, not a beam. It is still going to be at least 16" deep.
Going with a 10" deep beam is better than adding meat to an 8" beam.
There are folks here who could design steel or LVL beams for you. But none of us know what's available where you live. So trying to do so is pointless. You're better off finding a local supplier and having them design one for you.
Have ya thought about floor trusses? They could easily clear span the 25' direction, and then ya wouldn't have and beams at all. But they'd probably have to be 18" deep, more or less.
But wait! There's More....
Another issue nobody has yet mentioned ios how the roof and upper level are laid out and if any roof load will transfer to the floor system.
Floor trusses and roof trusses to place all loads on the preimiter equally are likely the best solution here