Another Flitch Beam Question

[TexasCowboy]

I am looking at opening a 24' span on a 36' wide room, single story, heavily reinforced slab, near San Antonio (No Snow). The rafters are 4 in 12, 2x10 16"oc and joists are 2x8. Decking is 7/16 with 26 ga roofing. One end of beam will be on cmu steel reinforced solid fill. Other end on 2x6 wall over 3' doorway. Considering flitch beam, 3-2x12 with 2-3/8 steel ½ bolts and same over door on 6x6 posts. Thoughts? - Thanks.

 

[JAE]

Can you clarify the location of the opening? Is it through a stud wall? Is the slab you mention a ground supported slab-on-grade foundation.
You mention both sloped rafters and joists - is the opening below the joists or below the rafters? etc.

 

[TexasCowboy]

Thank you for the reply. I tried to be complete, but nothing beats a site inspection and a good set of plans. The opening will be between the 8x8x16 CMU wall (reinforced storm shelter in main bathroom in middle of house) and doorway (main entrance on outside 2x6 wall) along the 24' span. The doorway is smack dab in the middle of the house. The rafters are 4 in 12, the joists are 0 in 12, they run the 36' width. It is slab on grade over 5' of packed crushed limestone and double #6 top and bottom in beams and #4 every 12". Beam is projected to be under rafters, 10' walls. Owner is resisting a post in the middle of the span.

 

[Ron]

I'm confused as well...could you give us a hand sketch of the issue?

 

[JAE]

I guess your question states "considering flitch beam, etc." Are you asking for confirmation of the size or whether this concept of a flitch beam makes sense in this application?

The flitch beam makes sense, but whether it is sized correctly you'll have to figure that out yourself or hire someone who can verify it for you.

 

[msquared48]

Sounds like you have a central bearing wall supporting the roof structure that you want to insert a 24' long beam?

Mike McCann
MMC Engineering

 

[boo1]

need a sketch

 

[msquared48]

Anyone home?

Mike McCann
MMC Engineering

 

[TexasCowboy]

Having some technical problems with my computer. Still working to get you the sketch.

 

[TexasCowboy]

Ok, here is the sketch. The span tables I have looked at are for ridge beams, Floor joists, or load bearing end walls. The flitch I am looking at just has to hold up the ceiling joists and the drywall. It may be oversized already, except for the flitch over the doorway.

 

[JAE]

In your first post you are asking for "thoughts". What exactly are you asking for?

No one here is going to (or should) check the size of this for you.
If you don't know how to size this beam, hire an engineer to do it for you. Probably only at most an hour of time.

 

[TexasCowboy]

Thank you for your response JAE. What I am asking for is an opinion, since the tables I reference don't cover my situation. I have found that a second set of eyes before starting a project is always better than 20/20 hindsight (I apologize for mixing metaphors to make a point). Obviously I have sized this member, as you can see from my specs. I feel it is more than adequate, and am asking for opinions. If you do not wish to make an opinion, I can respect that. What I am unclear of is the numeropus questions you ask, merely to state you feel I should hire an engineer and offer no opinion of your own. But that is your business. If I am out of line for asking for an opinion from fellow forum members, than I am under a misunderstanding of the purpose of this forum. Have a nice day sir.

 

[boo1]

Consider using engineered truss system. Dissuss with the truss builder options like storage, gable end, and overhang.

Alpine has a guide at:

http://www.pahi.org/sitebuildercont...lders-guide-to-trusses-alpine-engineering.pdf

 

[JAE]

TC - no problem.

Your original question "..thoughts?" many times are reflected in posts here where people ask for actual engineering sizing/services.

Your post sort of hinted that way and I wanted to make sure that you didn't depend on size "opinions" here as it is very dangerous to solicit and use sizes provided by anonymous people on websites in actual structures as those providing the sizes may not have all the facts and non-engineer types asking the questions may not know what facts are important.

 

[TexasCowboy]

Thank you boo1 for the opinion and the good information. I am also considering LDL as the cost of steel and fabrication can make the flitch expensive.

JAE, with your posted 8,329 replies, surely you have an opinion, or am I still having my credentials vetted?

 

[JAE]

Ask a specific question and we can get to the root of what you are looking for.
So far all you've asked is "Thoughts?" and "Opinions?".

I have lots of opinions. Which one are you looking for?
Is it this one: "Please state your opinion on whether the flitch beam idea is appropriate for this situation?"
I've already stated that my OPINION is that it is appropriate.

If you are asking my opinion on whether the size is correct or not I would refuse to help you as this site is not meant to solicit free engineering design services or checks.
If you are an engineer - post your calculations and we can comment on them directly.

And I'm not vetting your credentials.

 

[JAE]

I guess we don't get any calculations...

 

[boo1]

none are there, maybe "Engineering from a chart table"

 

[TXStructural]

I'll chime in. This is residential in Texas, 21 foot spans do not need to be sealed, but experience tells me that they do need to be engineered. The problem I see is that the full load path isn't described. I'm not exactly sure how the roof framing loads the new beam. Is there a line of support from the ridge to a wall being removed? The joists running perpendicular to the rafters means that the attic floor isn't providing restraint from spreading of the walls as the rafters try to pry the walls apart, as I would expect to see in a self-supported ridge. Also deflection will be a concern since your proposed long beam will bend between supports, but seems to be squeezed into the joist space. Since depth is essential to limit deflection, I would not try to squeeze the beam into the height of a 2x8.

I removed a wall down the center of my house, replacing it with a four foot deep truss constructed in the attic. It is holding up well (no pun intended.)

 

[TexasCowboy]

Thanks TXStuctural, I was concerned with spread as well. Ran costs of Steel plus fabrication and LDL is looking better all the time. I am still trying to convince owner to put in a post.