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The Home Smithy
The Home Smithy, Home Builder
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Experience:  #1 Home Improvement Expert 30+ years experience
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How do I calculate the strength of a beam. Im trying ...

Customer Question

How do I calculate the strength of a beam. I'm trying to remove posts from basement to gain greater clear span. I have 27 ft of 3 - 2x10s nailed together with 3 columns approx. 8 ft apart. The area under consideration is 715 sq.ft. The 2x10s used to construct the beam are not continous. The floor joist are also 2x10s. The stairwell to the basement is located against an outer wall as is the stairwell to 2nd floor. I say this because around 3-1/2 ft of the beam is not seeing much of the load. The total dead load is 25,977lbs. The beam is pocketed in a 8" block wall. Also the beama is not central in the house it is 13' from the front and 12' from the rear walls. The roof load was not considered asthe ridge rests onthe gable ends and there is no supports to the 2nd floor ceiling. Whatever cure I use it can be installed from the outside an fed thru to the opposite wall. Can I thru-bolt 2 pcs. mild steel 27'x9"on ea side of beam? I can't add height to existing beam.
Submitted: 8 years ago.
Category: Home Improvement
Expert:  The Home Smithy replied 8 years ago.

Hi Roscoe;

To support the whole load on something that is 27' long on only the outer block wall is going to require that the block wall not be involved in the picture. 25,000 pounds is just too much weight for the block wall alone to bear as well as the wall loads that it also must handle.

What you are going to have to do is pour footings on the exterior of the home of sufficient size to carry the load.

Th footings will require a set of post beams (most likely steel I beams) be set into them.

Once this is done the beam that supports thew actual load can be moved into place and then either bolted or welded into its final position.

Ok I am sure that you would like for me to tell you what size the beams and footings are.

Unfortunately I can not. This is a job that a qualified structural engineer will have to do.

Now mind you this is not because I can't tell you the size beam you will need as I have worked as a steel fitter, millwright, and a carpenter. All of these jobs require that you know something about how much weight a member can withstand.

The problem comes in with the fact that I can not see the actual structure. I have no idea what type of soil you have, or quite a few more things that would be required to form a proper assessment of the job as a whole. Not to mention that it would be illegal for me to give this advice with out an engineers certificate.

Best advice: Consult with a structural engineer in your local area.

FYI, a 1" x 10" x 8" steel I-beam will hold the load. Gussets may be required near the center to prevent twisting.

If this answer satisfies your question please click on the accept button. If it does not, please tell me so. You are not expected to accept any answer that you are not happy with.
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Best regards; The Home Smithy
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The Home Smithy, Home Builder
Category: Home Improvement
Satisfied Customers: 9619
Experience: #1 Home Improvement Expert 30+ years experience
The Home Smithy and other Home Improvement Specialists are ready to help you
Customer: replied 8 years ago.
Thanks for your input. I am going to consult a structural engineer on this one. I feel more comfortable that way - someone else assuming responsibility for the decision. I was just trying to figure it out on my own is all.
Expert:  The Home Smithy replied 8 years ago.


Here is a quicky sketch of what I'm talking about. Show it to the engineer. Im sure he will agree that it is a viable method to accomplish what you want.


Thank you for accepting.

Best regards; The Home Smithy

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