Question: Steel Beam size

Fri 10 Sep 2010 - 8:24 pm UTC

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ANSWERED on Mon 14 Dec 2009 - 6:13 pm UTC by redhoss

Question: Steel Beam size

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Asked by wallyg on Sat 12 Dec 2009 - 7:00 pm UTC:

I'm in the process of expanding a room in my basement. The house was built
in the 50's, the homeowner was an industrial builder and built this house
with cinder block,hydraulic cement and steel beams! (basement area) The
second floor is wood consctruction with lath/plaster walls.
The rooms in question are 9x14 with a 8in thick cinder block wall which
runs east to west between them. That's the wall I want to eliminate.
The tricky part is that the ceiling above these 2 rooms is poured comcrete
which is 13in thick. There is a small I beam (6in h x 4in w) that runs
north to south which is supported by the 2 foundation walls at each end.
The room above this space was at one time an outdoor patio area, but later
was closed in and renovated to become a family room with 20 foot ceiling
height, so there is no weight in the center (room above is 14 x 18)and is
mostly glass windows on 3 sides. (sorry for long explanation but necesary)
I want to knock down the wall and support the concrete ceiling with a I
beam that will be supported by cinder block walls on each side.
Can you help me figure out the appropriate beam size for this job?

Uclue Researcher Request for clarification by Researcher redhoss on Mon 14 Dec 2009 - 4:04 pm UTC:

Hello wallyg, I think that I understand your layout. You have a 14' x 18'
room with a 13" thick concrete ceiling. There is a room above that is also
14 x 18 with no load bearing walls. So, the beam we are designing will span
14' and have a loading that equals the weight of the concrete plus a
standard living area live load (say 40 psf). I am not clear on which
direction the 6" beam runs. Does it span 18'. Will it rest on top of the
new beam. I assume the 18' direction runs north/south? Am I getting close.

Question clarification by wallyg on Mon 14 Dec 2009 - 4:46 pm UTC:

Yes, you are right. The room below, where the wall we want to remove is
actually 2 rooms that are 14x9 with the wall in between. The 6 in beam runs
the 18ft length (North/South) and sits below the concrete, so the new beam
would go "across" it and below it. So the 6in beam would sit on the new
beam only in the section where they cross at center point. The new beam
would be sitting on the cinder block walls at each end and both are main
supporting walls.
Once we have the beam size, should we fill in the open space above the new
beam (6in void between beams) our plan was to fill it with brick and
cement.

Uclue Researcher Answer by Researcher redhoss on Mon 14 Dec 2009 - 6:13 pm UTC:

I looked at this beam two ways. One with a point load applied by the 6"
beam and then using the load applied uniformly along the 14' length. I used
a total load of 202.5 psf. I got the total load by using a concrete weight
of 150 #/cubic ft and the 40 psf live load already discussed. As expected
the two answers came out almost the same. I also ran the numbers in a beam
program to confirm my calculations. The best beam for your project would be
a W12x19. You could also use a W10x25 if there is a headroom issue. I
wouldn't fill the void above the beam with bricks and mortar. That would
only add to the load and possibly risk pieces of cracked brick/mortar
falling. Even though a beam is very strong it still deflects under load and
cracks will happen. If I wanted to fill the space for asthetic reasons, I
would consider using fake brick panels or such. Please ask for a
clarification if you have any questions. Good luck with your project,
Redhoss.

Accepted and rated by wallyg on Mon 14 Dec 2009 - 7:51 pm UTC:

Thanks, great response speed. Very knowledgable. Thanks

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