We are drawing plans for a new house, and would like to use a steel beam instead of support posts in the garage. The garage will be on the basement level, with 2 stories above it-living room on first floor, bedrooms and 1 bath on second. The roof is gambrel, this truss does not add any psf for the roof. Garage dimensions are 36'x36' and foundation will be poured walls. What size beam will we need?

Without seeing ann exact cross section of the area you are talking about, and without examining all the actual conditions which might affect thge design of a beam, it is not possible to answer your question.

However, a beam spanning 36 feet will be either a very deep beam or a very heavy one. You would probably be quite surprised at the size required. Even one post would make the beam much more practical.

thanks for the response. i did wonder if we were setting our hopes too high...a 36x36 garage with no posts. i would just take our plans a company selling steel beams, but we've found a couple of beams for sale used, and the man doesn't know the load they can handle. i was hoping to find a chart which would show spans/weights.

No such charts exist for steel. What you have to do is identify the beams that are available. Steel nomenclature gives the type of shape, then the depth in inches, and then the weight per foot of the beam. For example, a W16x26 beam is a (W)ide flange shape, is 16 inches deep give or take a fraction of an inch, and weighs 26 pounds per foot.

Then you have to calculate the maximum moment that would be on the beam in your application, and determine the Section Modulus of the beam that would be required, and see if the beams you are looking at meet or exceed the Section Modulus required. There are other checks that should be done also, and then the footings under the posts at each end of the beam must be designed to carry the loads that will be coming down on them.

I think your best bet would be to contact a civil engineering firm to help with this. You don't want any guessing, especially with used beams. Money well spent in the long run.

As with any construction project, you would be well served to consult with a licensed professional engineer regarding any aspect of the structure.

This is in response to jkb. We have a garage (plane hangar) thats 50 ft x 40 ft (13'high)with no posts and a whole second floor built above it. We have 3 - 48'long beams x 2ft deep with a 9 inch flanges. The KSA's on these beams is 76. There is a chart out there on the web that will let you calculate what strength beams you need depending on the span.

We did the construction ourselves and just to make sure I verified the integrity of the beam specs with an engineer and he agreed with our specs. It's not as complicated as it sounds.

p.s. We ordered the beams (AS PER OUR SPECS) and the cost was about $7600.00 for all three (including delivery).

As someone who has installed quite a few steel beams. There are many more variables when you are looking for the right size beams, do they need stiffeners, gussets, etc.. You will also need to find out what size posts and footings to hold up the building. The first thing you need to do is talk to a structural engineer. This is one part of your home that you should not skimp on. The used beams may be the right fit but let the engineer say that they will work. Good Luck!

If only you lived in or near Seattle. We frame our entire homes in steel. Clearspans of 50' are not uncommon. Most definetly, consult a structural engineer.

Richard Hetzel, There ARE charts... American Institute of Steel Construction... Manual of Steel Construction... $300+... which is one reason we civil engineers (registered professional) charge a small fee for verifying the loads and recommending the beam size. We would also make sure it is anchored properly and other considerations... that is what we went to school for... to know what to look for.

That is why one should always consult a structural engineer in such matters...

Just for the heck of it, the reason such a deep beam would be needed is because it is simply supported; if the beam were made continuous over several supports, some of the strain energy could be absorbed via negative bending moments, reducing the maximum deflection at any point, and thereby allowing a smaller section to be used.

The size of the beam necessary also demonstrates why another handy structural element was invented... the TRUSS!

Respectfully yours,
da Moose

Have a structural engineer who is registered to practice in your location, design the beam, columns and foundations, and write a specification as to how the work should be done. This should not be treated as guesswork.

Moose, yes, there are charts, which can only be used once the load is calculated, and several other criteria are checked. That was exactly my point. We all agree that it is not to be solved by guesswork, and an engineer or a competent architect should be involved.

I am an electrical engineer in Kentucky and would fully advise you, as other professionals have on this thread, to hire a structural engineer to evaluate the design. This is critical, since you don't want to make any mistakes about the structure. If you make a structural mistake, it can be incredibly expensive and even dangerous. Spend the $ and get good, professional advice. It will be well worth it and when you sell the property, you can certify that it was done right.

Hope all goes well with your project.

Kyphil

I do not have an answer, however, I am considering the same and wanted to hear your thoughts on resell with a basement garage. I am assuming I will save a lot of money with eliminating the garage structure but wonder about resell value. I have an engineering staff that will calculate the beam question.

quote:

Originally posted by jkb:
We are drawing plans for a new house, and would like to use a steel beam instead of support posts in the garage. The garage will be on the basement level, with 2 stories above it-living room on first floor, bedrooms and 1 bath on second. The roof is gambrel, this truss does not add any psf for the roof. Garage dimensions are 36'x36' and foundation will be poured walls. What size beam will we need?

quote:

but we've found a couple of beams for sale used

I think you all missed this part of the original question. There is, I repeat, no chart that will identify a used steel beam beyond a shadow of a doubt and tell anyone what load it can carry. So, the first question is, exactly which steel beam is it? The only thing worse than using a used steel beam without knowing what it is would be to use a used truss. Trusses don't enter the picture here.

If you know exactly the loads required by code that will be carried by the beam, and you know exactly what size and designation the beam is, that's about half the battle. Do you then know how to calculate the end reactions, how to design the beam to column connections, and how to design the column to footing connections, and then how to design the footings required? If so, go ahead and design your garage. If not, find someone who does.

To answer the other question, you'll be balancing the cost of one or more large steel beams, the cost of a crane to erect same, and the cost of a couple of fairly large column footings, plus the cost of fireproofing the beam or beams, against the cost of another structure of unknown design, so It's hard to answer any questions about cost. As far as resale value, I doubt that it would add one cent to the value of the house.