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walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2833
Experience:  Over 30 years of Structural Engineering experience.
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How far can I span a 4" steel I beam without a support post

Customer Question

How far can I span a 4" steel I beam without a support post
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  walkereng replied 1 year ago.

I can help

Expert:  walkereng replied 1 year ago.

Can you get me the depth of the beam, the width of the beam and the flange thickness of the beam to the nearest 1/8"?

Expert:  walkereng replied 1 year ago.

With this information, I can look up the actual beam size in the AISC tables

Customer: replied 1 year ago.
I'm not sure. I need a beam no more than 4" tall to span 22' 6" to support floor joist that span 18' @16 o.c.. I would prefer not to use a support post. The beam will run through the webbing of engineered floor joist so I am limited on beam height.
Customer: replied 1 year ago.
The existing joist are sagging. We don't want to a beam on the outside of the ceiling and no post. The plan is to cut a hole in the side of the house and slide the beam through the webbing of the joist.
Expert:  walkereng replied 1 year ago.

So you want to slide a beam at the midspan of your 18' span floor joists, so you will be making two 9' spans more or less to help support the sagging existing 18' span floor joists?

Expert:  walkereng replied 1 year ago.

Are these floor joists in a bedroom area or a general occupancy area in your home?

Customer: replied 1 year ago.
Family room in the basement. Yes the beam would create two 9' spans.
Customer: replied 1 year ago.
Sorry the family room is below and the bedroom is above the joist
Expert:  walkereng replied 1 year ago.

Sorry to say the shallowest Wide Flange beam or Structural Tube are both 8" deep. A 4" deep member will not span 22.5'.

Customer: replied 1 year ago.
Could I span a 4" with one post in the middle? Weigh is an issue as well. The beam needs to be moved by hand.
Expert:  walkereng replied 1 year ago.

I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.

With a post in the middle of the 22.5' span, you could make two spans of 11.25'.

You could use a W4x13 (50 ksi) steel beam. This beam is 4" wide and 4.125" deep. The beam weighs 13 pounds per foot of beam.

If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each adequately Rated answer they provide. If you have additional questions, please let me know. Thanks

Expert:  walkereng replied 1 year ago.

Let me know if you have any more questions