help with support beam question.

[the nitro man]

Hi, this is my first post, so hello to every one.

I'm building a 28'x28' garage with a 28'x28' second floor on top for storage & maybe a play room. i was wanting to use 11 7/8 I joist to span the 28' without any support beams in the garage section, but found out today that is way to much span to do without the supports. i can't afford to go to the 16" i joist. they are double the cost of the 11 7/8 & will need to go on 12" centers.

How can I do this without having the support beams on the garage floor? I was thinking about using a steel beam, but I have no idea of what size beam I would need. how can i figure out what i would need, or is there another way?

a support beam in a garage is a dent in a car door waiting to happen. That's why I want to stay away from them if I can.

Can someone help me?

Thanks for your time & help.
Jerry

[DEW29]

Hi Nitro man,

You have several options if you don't want a column anywhere within your 28 x 28 floor space, but I am sure it is going to cost you. You already looked at deeper I-joists at 12" O/C. You can span the 28 ft with a beefy parallam beam, probably around 7"x20" if you only intend on a play room and will have no heavy storage on the 2nd floor. And for steel, you are looking at something like a W16x26 or maybe a less deep 14x30. These steel sizes wouldn't allow for heavy storage either. You can even go to a 12" deep steel beam if headroom is an issue, but again it will be heavy which makes it more costly. Your floor joists will then only be spanning 14 ft, which is more reasonable. All of the above is assuming that NO load from the roof will be on these beams (2nd floor load only). If you do plan on throwing some bulky beams like these into your garage, I would recommend having them engineered.

[Don_P]

Don't forget an attic truss also.

[Michael Olding]

Dew, If you know it might not hurt to tell him how much a steel beam or a lam beam is going to weight so he has an idea of what it will take to set it in place.

If he is doing a cost benefit analysis then he should know the cost of beams as well as the cost of setting them into place. Not just curb side delivery cost.

Just a thought.

[the nitro man]

how big of a parallam beam would i need? where can i buy this? lowes or home depot?
i found a place where i can get 28' one piece 2x12's. could i get buy just using them on 16" centers without any support beams?

thanks

[homebild]

how big of a parallam beam would i need?

-Only an engineer can determine this.


where can i buy this? lowes or home depot?

-You will need to contact a professional lumber supplier. (Lowes and Home Depot usually do not qualify as 'professional lumber suppliers'....at least in my region)


i found a place where i can get 28' one piece 2x12's. could i get buy just using them on 16" centers without any support beams?

No. Maximum span on 2x12s 16" on center will be about 17 feet (#2 grade Spruce-Pine-Fir).

Even if you went with Structural Select Douglas-Fir at 12" on center, the maximum span you can achieve is about 23 feet...well short of the 28' you need.

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I'm with Don P ojn this one. Consider using some roof trusses engineered so the floors can support the 30-40psf load you would need for the playroom space.

[the nitro man]

Someone at work mentioned using a laminated beam. Anyone have any experience with them?

[DEW29]

Don P. and Hombild have my vote, the engineered truss is probably the best place to start.

Just to fill in some blanks:
7"x20" parallam will weigh about 44 lb per ft. Check out i-level or Boise Cascade websites for these types of beams.
W16x26 steel beam will weigh 26 lbs per ft.
W14x30 will weigh 30 lbs. per ft.

[Don_P]

My computers been burping, Dew posted most of it but some of this might help with understanding the problem.

Let's figure the load and look at beams;
50 pounds per square foot total floor load (40 psf live load+ 10 psf dead load). No roof load, the roof is borne on the walls alone. Run a glulam beam down the center of the 28x28' building. From the center beam to the wall on each side, half the load bears on the beam, half bears on the exterior wall. This happens on each side so 1/4 the floor load is on one wall, 1/2 bears on the center beam and 1/4 bears on the other wall. Or another way, the center beam supports a swath down the middle of the building 14' wide x 28'long. or 392 square feet of tributary loaded area. 392 x 50 psf total load = 19600 lbs on our center beam thats 28' long. divide that by 28' = 700 lbs on each foot along the beam. Those loads are what your beam needs to resist, whatever the beam material.

You asked about laminated beams, I assume glulam, horizontally glue laminated 2x8's in this case.
http://www.aitc-glulam.org/pdf/Capacity/DF_27.PDF
Scrolling down I got a 6-3/4 x 21" deep beam

You can look up parallam for the load and span under
http://www.ilevel.com/literature/TJ-9000.pdf

To answer Michael's question in steel the second number is lbs per foot so A W16x26= 26 lbs/ft X 28' = 728 lbs in a 16 inch deep wide flange beam.