Sizing for a residential steal beam.
Sizing for a residential steal beam.
(OP)
As a mechanical engineer I have a tendency to question things but structural engineering is not my expertise. I hired an architect for a full house redesign but I think his beam calculation is off. The current beam is W8x15 with a single column which I'm looking to remove.
Details:
Single floor (bedrooms)
Span length = 18ft
Tributary width= 10ft (2x10's on 16 oc)
Using the AISI Residential Steel Beam Span tables and a 40psf for the live load and a 20psf for the dead load I'm coming up that a W8 x10 beam will be sufficient. The architect is saying I need a W8x48 beam which seems to be a little overkill.
Am I looking at this right or am I just dreaming about not having to change out the beam since I'm doing the work myself.
Thanks for the help,
Steve






RE: Sizing for a residential steal beam.
Additionally, I don't do residential work so it's possible there is a more stringent deflection criteria.
Finally, vibrations should be considered. You would hate to get woken up from a good sleep because your kids are jumping in the next room, right?
RE: Sizing for a residential steal beam.
I would suggest asking him, if he works for you, you should be free to ask and he should be able to justify the choice of beam size.
RE: Sizing for a residential steal beam.
Steve
RE: Sizing for a residential steal beam.
RE: Sizing for a residential steal beam.
RE: Sizing for a residential steal beam.
RE: Sizing for a residential steal beam.
attics with out storage = 10psf
attics with storage = 20psf
Also, for a new beam in an existing house I am pretty strict with deflection. The limits I use are referenced against total load deflection.... not live load. The last thing I want is the plaster to crack or the doors to not work because there is a deflection problem.
RE: Sizing for a residential steal beam.
RE: Sizing for a residential steal beam.
Beam comes in at 39% - very conservative - but defl is the problem....
If you really want little deflection - try a W12x22 --- less than .33'' total deflection - but your clear basement ceiling height might suffer. Or use two or three sill plates to raise the level.
RE: Sizing for a residential steal beam.
At a quick glance it looks like you're closer, but a little light. Although, to have him redesign it, he will likely defer to an engineer. You would then need to pay the engineer to design the beam; which would likely not save much expense, unless there are numerous beams to save on bulk.
For example, a W8x48 will run you about $688 at the plant and a W8x18 would cost about $258; which will save you $430. A nice chunk of change, but an engineer will probably charge you a minimum of $300 dollars to design and seal it, so your down to $130 savings and your Architect is not very happy with you.
Although there appears to be alot of waste, I would probably tell you to leave it alone. Just my two pennies.
Best of Luck.
RE: Sizing for a residential steal beam.
RE: Sizing for a residential steal beam.
Mike McCann
MMC Engineering
RE: Sizing for a residential steal beam.
There is currently a nailer but my plan is to through bolt two 2x8 lam beams on either side of the beam and use joist hangers so I can recess the beam into the ceiling.
Thanks for the help,
Steve
RE: Sizing for a residential steal beam.
He's acutally real close if not on with what he says (if you're concerned about deflection, which you should be).
Your existing beam deflects much more about 3/4 inch if you use it, too much. I would never attempt to use it augmented with 2x8 glulams.
Get rid of the architect, if he cannot show you calculations, he's no good. It's not that hard, I'd hate to think it but now you have to question if he knows the residential code in your area and what else is he winging.
You also have to question his judgement and common sense.
Get someone who knows what they are doing.
The 2x8 lams won't help. Spend some time and look up a flitch plate, which is what I think you want to do (sort of). They require fastening all along the beam to transfer forces properly between the steel and wood (through bolts).
You can check with your local code folks and ask them to show you residential plans (already approved) where the second floor is the only loading and the span is 20 feet. They will show you as they are public records. Explain your concern without naming the architect.
He's probably right on because once along time ago he paid an engineer to do the calculation but the calcs are marked with the date, owner and engineer who did the calcs.
Good luck.
Dermott
RE: Sizing for a residential steal beam.
I won't even try to give you yet another opinion about an appropriate size for your beam, but am sure you are confused and dismayed by the variation.
Pay particular attention to the comment by SteelPE about installing a new beam in an existing house, and consideration should be given to preloading the beam by wedging against the floor joists.
You should get a better answer by hiring a structural engineer who is responsible for the design rather than depending on an architect or this forum.
RE: Sizing for a residential steal beam.
Regardless of the cost (i.e. low fee), the engineer doing this calculation SHOULD make a site visit.
Anyone who does not is not taking it seriously. They should also be taking their own measurements and photos.
They should provide you with the calculations if you ask them.
Be there when they visit, you'll learn alot.
Good luck,
Dermott
RE: Sizing for a residential steal beam.
You have doubled the load on the columns at either end of this beam, they are probably currently a couple of 2x4's. They will probably need to be increased.
Construction of this type is governed by the state building code, possibly with supplements locally.
New code was issued for NY State on 1 Jan 08. Other states are different.
Good luck,
Dermott