How Many Support Posts Do I Need, and Where for My Support Beam Load?

I agree with Jpool, you didn't provide nearly enough info., don't fool around with internet help.get someone "one the ground to perform their proper due diligence and build it right the first time, don't go cheap!

Hmm. to Jpool and Fredski, much thanks. I live two doors down from a PE who is current on structural engineering, and with whom I have a good relationship. I'll have to show him the question, and see what he would say. He definitely is the one on "the ground to perform their proper due diligence and build it right the first time"!

I need to either learn to spell or stop multitasking so much (good luck on that)

My basement and house setup are identical, except rather than a steel I- beam, my main beam is comprised of three 2 x 12's sandwiched together and running the span.

My house was built in 1983, and the run is supported by three vertical 4" steel posts, spaced about 6' apart, with the two on the outside being about 6' from the wall.

Considering that mine is wood, I'm sure this would be totally acceptable for your application. Steel beams generally require less support than wood though, so it might be overkill.

If three supports won't get in the way, I'd go with that. Otherwise, I'd call an engineer. Two, or possibly even one, might be adequate.

when I read his post I was more focused on total weight transfer and the quality of footings accepting the new loads, The I-beam is more than enough

So, on second thought, you are suggesting that if the support wall at the front of the basement (block on top of concrete footer), and the support at the back (native rock!) are enough, the span is not excessive even without additional support? Our intent is to use at least one, probably two, and possibly (depending on professional advice, which I intended only to START, here) three columns, with the intent that all sway in the floors above be eliminated. To that end, our intent was also, once we cite the proper column spacing, to dig/pour footers which will be tied under the over-lying concrete slab.

Thanks again for your help.

Thanks. This, too, is useful. His current situation is two steel columns about 8 feet apart in the center of the span, but one end of the span rests on a solid block wall over a concrete poured perimeter footer, and the other rests on the original back wall of the basement, which is solid rock. He wants to use less columns on longer spans, if possible, but knows he has to completely rebuild that back wall, as that is where he doing the most of his excavating. He already plans to pour individual column footers, as part of the pour of his new concrete floor. I was up in Central Pennsylvania helping him dig out and level the floor two weekends back. The next step is getting the materials in to complete the prep for the pour.

Don't assume that the floor will support the load transferred onto it locally by any additional columns!

That is why a Structural Engineer is needed, rather than relying on a few comments from anonymous CR4 readers who cannot see, measure or assess the proposed installation and are not liable in the case of structural failure.

I just jumped back on to amend my last comment.

If it was my house, I would place two vertical steel posts about 9 1/2' on center, spaced from the walls. I would also dig out and pour footers underneath them. But that's just me. I also used a floor jack and two 2 x 4's to hold my second floor in place, while I ripped out a load bearing wall and put in a wooden column.

PWSlack - I'm trying to get a handle on the meaning of this "Don't assume that the floor will support the load transferred onto it locally by any additional columns!"

I come here to learn, and I do. But this one makes me want to suck out your knowledge so I can sort it with a fine screen for the tidbits. Please, I can't figure out what you are saying and it ingtrigues me as it undoubtedly is going to bring up something of which I never even had a glimpse.

Would you please come back and straighten me out on this?

Doorman:

Thank you. Can you send me a copy of this drawing in JPG or other graphic form, via PM? I can't read the details (drat that low-def message window), and would definitely like to learn the details herein presented.

Thanks

can you send me a check or are you looking for a freebie? jk...at this point I think you need to hire someone, your beam is great if you have enough columns that transfer the weight of the building to quality footings

good luck

We'll find out, in detail. Thanks.

Ooops. Should have credited the image.

Taken from ARCXL. A .pdf version can be had there.

That is a generalized detail of a thickened slab used under bearing walls and columns. Any particulars in the image will likely not be applicable for you; the thickness, reinforcing, and width/length are all sized for individual applications, these sort of hinging on the concrete spec.

Thanks. Got that. I'll show it to my son as proof that he needs to get this designed by, or at least advised by, a professional.

I agree with the others here, discuss this existing construction with a Registered Structural PE in your state.

Without professional help, one single mistake made by your son during the renovation could spell disaster....

Just curious, is that existing steel beam actually spanning 28 feet, or is that the overall length and there's intermediate supports (columns or posts or bearing walls)?

Typically, intermediate spans between posts or columns in residential structures usually are less than 12 feet on-center......the actual maximum spans will be based on a number of factors: total loads, material grades of the steel for the existing beam and also new steel columns, and the bearing capacity of the underlying soil mass which dictate the design of the column isolated footings.

Posted here to include all of you, thank you very much for your timely replies. I/we will take all of it to heart, and get professional on the ground advice later this week (my neighbor is energetic, and can be hard to run down) (figuratively, I LIKE him!) from my neighbor.

I'll also be checking back regularly for any updated info you or others may post.

And PWSlack, I'm looking forward to hearing again from you. I still want to understand exactly what you meant in that post.

Thanks again, to all of you. As I have come to expect, CR4 is my go to place for info on fields of engineering for which I don't have a handle, or need more specific and qualified info than I have available. And you all came through again.

It's simple. No reader here can see the installation though the potential pitfalls can be highlighted. A local Structural Engineer is in the best position to observe, review, calculate and advise, and a job of this type needs that technical input to save the house from falling down, killing someone and the home's insurance company from walking away from it.

In the UK, the design calcs form part of the detailed Building Regulations application that needs to be lodged with the Local Authority, who will review and either require changes, or approve, thereby endorsing the design, providing a level of assurance that the design is valid.

At the moment, all that is available is a scheme, based on ideas, arm waving, and a handful of comments from anonymous strangers on the internet, however well-meaning those comments might be or otherwise.

So get professional help. Get it down on paper. Get it approved before starting.

And don't do business with friends.

[The End.]

_{<unsubscribes>}

I agree wholeheartedly with PW in post #20. Relying too much on the statements of peeps over the net is not the right way to do things, especially since they haven't observed the actual conditions in that house......nor have they even conducted structural calculations.

Although Doorman's posting of that "haunched" floor slab detail has some merit, I would not go that route in your case if you're going to install posts (aka columns) along the existing steel beam. You're better off served with square isolated reinforced concrete column footings under the basement slab on grade. I don't think that a haunched footing will be able to support the concentrated load induced by the column.....it may actually "punch" through the thickened slab. Also, the effective bearing area of a thickened slab may not be enough to support the total design load and you be experience soil bearing failure.

Also, with square isolated column footings you will save $$$ and time in materials and effort. I recommend at least a minimum of 12-inch footing thickness.

Assuming that the roof and attic (if it exists....verify please) is not contributing any load, and that the existing steel beam is supporting only 2 floors....also assuming that the house is 30 feet wide.....and using 8-foot o.c column spacings:

We're looking at a Total Design Load = 15,120#, give or take, at any given column.

Assuming a Presumptive Soil Bearing Pressure = 2,000 psf (we don't know the soil characteristics and ultimate bearing capacity), results in a minimum square footing area of ~ 7.6 S.F., or 2.75' x 2.75' footing. Personally I would opt to bump that area up to at least 9 SF.

If the roof and attic contribute load to the entire scenario, then all bets are off and that footing area must be adjusted upwards significantly.

All said, the existing steel beam should be analyzed to insure that it can carry the superimposed loads safely.

Please take the advice of others and myself and hire a Registered Structural Engineer. Believe me when I say this. I've been during this sort of thing for over 35 years.....

good points but he never did offer a total weight or how the house was to be used(hopefully no water bed in the corner of the room granite and marble flooring everywhere, etc.........unfortunatly we're let to assume/guess much.....no photos, drawings, material lists, etc. it all comes down to vague suggestion based on few details

EXACTLY!!!!!!

I have done these in the past and it turns out that the number of post spaced as they are currently is the number needed for the beam used. In order to remove the post, beam will have to be replaced, most likely. I have suggested in the past to others, look at doing remodel in another manner. Too costly other wise.

Now as with all advise I may give, its your choice to listen or not. I could be wrong, without seeing more data and the site itself.