# I beam requirements calculation

by paul
(huntsville AL)

saferoom

Question:

I followed thru with Lou's example calculation of I beam size for supporting concrete ceiling-- but find myself questioning my results...

I am planning to build a 12.5x10 saferoom within my basement--utilizing 2 existing 12" block walls and building 2 additional walls. I plan to pour a 4" concrete ceiling.

I plan to cut hole(s) into existing 12" block walls to support one end of the I beam, and likewise into the new walls.

My questions:
1) should the beam run parallel to the 10 ft dimension or the 12.5 ft dimension?

2) is one beam all that is needed?

Using Lou's example, I came up with S=1.6, and a W4x13 or W6x9 meeting the requirement.

I plan to use 3/4 plywood and sheet metal for in-place form support. How many vertical supports and what spacing required during the pour?

Thanks!

Hi Paul, thanks for visiting all-concrete-cement.com

First lets double check the numbers:
Flooring - 5 psf
Ceiling β 3 psf
Beam weight = 10 plf
Total dead load = 58 psf x 5ft = 290 plf + 10 plf = 400 plf
Total live load: 40 psf = 40psf x 5ft = 200 plf

Total load = 400 plf + 200 plf = 600 plf
Moment equation: wL^2/8 = (600/1000)*12.5^2/8 = 11.7 k-in
S = M/Fy = 11.7/(.66*50) = .4 cubic inches

As you can see, I have much less S required for the load than you came up with. There are number of reasons as to why this is, one being the dead load that you used but itβs very less likely that the dead load will be much different.

Based on my calculations, any steel beam I beam that you want to use will work.

The 10ft x 12β-6β is pretty small for steel frame - steel in most cases are used for 20+ feet long span.