[bluehorizons]

Hi folks. Hoping someone can point me in the right direction here. I want to reconfigure some load bearing walls in my house using LVLs, and have everything sized correctly, installed and approved by the County. But now I want to move slightly some columns in the basement. I know the load that the column will carry and it is on the order of 6000-7000 lb. I'm going to use a triple 2x4 for the column itself, and based on the local soil bearing capacity (2000psf) I think I can get away with a 22x22x12 square footer, but might just bump it to 24x24x12 just to overbuild it, but regardless I'm stuck on two things.

Firstly, what reinforcing requirements are there? Is there actually anything in the code book that requires rebar, and if so what size / how many bars / what placement locations? I mostly see reinforcing requirements for foundation walls/footers but not seeing anything jump out at me for square footers that will go in a basement and support a simple column.

Secondly, what about the attachment / connection method to get the 3-2x4s connected to the slab? Can i just use a short piece of pressure-treated framing the same way we frame typical basement on-slab stud walls? Or can I use some of the mechanical connections like Simpson offers for post base connectors? Again not sure what is required from a code perspective and just looking to have this correct when I submit for my permit.

Thanks in advance, and hopefully I haven't left out any vital info but if so please let me know and I'll add what is needed. I'm just having a bear of a time finding anything and the local permit office is being anything but helpful...

Thanks!

Matt

 

[joed]

"I think I can get with" is not good enough. You need it to be engineered by someone who knows for sure.

 

[bluehorizons]

Thx for the reply, but ok apologies for the confusion - let me rephrase: I know that the footing sizes are correct, as I used the appropriate calculations based on my design loads and the local soil bearing capacity. All I need to know is whether or not reinforcing is needed in square footings supporting a wood post for a basement and also the approved connection methods. Hopefully that clarifies. Thanks in advance.

 

[Daniel Holzman]

You don't say where you are, or what code you are designing to. The ultimate authority on what local code requires is your local building inspector. You may want to check with them first, they may know exactly what rebar configuration is needed, and they can certainly verify that you have an appropriately sized footer.

As a point of interest, column footers are normally reinforced to allow the concrete to resist diagonal shear. How much reinforcing is needed is either computed by a structural engineer based on the load, geometry of the footer, and the strength of the concrete, or is taken directly from code.

 

[bluehorizons]

great thanks. where would one look in the code for the amount of reinforcing needed? i'm in virginia, and am getting zero help from the local building officials unfortunately. they're happy to tell me if my submitted permit passes or fails but other than that - for some unknown reason - unwilling to talk concepts. Governing codes are 2012 VA Residential Code.

I'm hoping to avoid hiring an engineer for what i thought was a straightforward problem.

 

[jomama45]

Our code doesn't require rebar in the column pads. Ocasionally, we get redidetial blueprints that do require them. If it were mine, I'd lay at least 3-4 - 1/2" rebar each way about 3" from the bottom of the pad. Cut them at 20" for a 24" x 24" x 12" pad (which is the minimum allowable pad here by code).

I wouldn't use wood for the culumns either, considering how cheap and strong steel posts are. Not to mention, I doubt 3 - 2x4's wil come close to carrying the weight you're talking about..........

 

[Meanderthal]

I'm not aware of any code that prescribes the reinforcing for isolated footing pads for residential or any other type of construction. In my experience they are always engineered.

That said, if your calculation of 22" square is correct then I doubt that any more than 5 pieces of 1/2" (#4 ) or 4 pieces of 5/8" (#5) each way should be needed. The bars should be placed 3" from the bottom and not closer than 2" or further than 3" from the sides of the forms. Also make sure that your column is properly attached to the footing.

To be clear though, I absolutely would not pour the footing without any reinforcing regardless of whether it was allowed or not. Concrete by itself has very little tensile strength, and rebar is a cheap and easy way to solve that problem.

 

[Daniel Holzman]

Take a look at this website. The steel reinforcing is likely more than you need, but since your building inspector apparently will not discuss reinforcing with you, and you would like to avoid hiring a professional to design the footing, this is a good place to start. http://www.oas.org/cdmp/document/codedraw/sectionb.htm

Note that this website states that isolated footings always need steel reinforcing. In my experience, this is certainly true for commercial and industrial projects, and on the rare occasions when I do residential work, I follow American Concrete Institute (ACI) practices, and include reinforcing for the footing. Since I am not your engineer, I cannot legally or ethically recommend specific reinforcing, however Jomama has presented a reasonable approach that you may wish to consider.

 

[bluehorizons]

Thanks folks - I appreciate the comments and perspectives. I'll report back with any info once the building officials communicate back.

I very much appreciate the responses.

Best,

Matt

 

[Aggie67]

The reason your code official is backing off is because your project sounds rather non-prescriptive (use of LVLs). He probably doesn't want the liability associated with telling you what to do.

 

[Trout]

This seems to need more than an online forum to address properly. If you have beams, posts, footings, and rebar to consider in your design you probably need an engineer. There are almost certainly things you are overlooking.

You say you have things sized correctly: how did you accomplish this?

It sounds like you would like to significantly alter the structure of your house. I would be hiring a professional. If it's straightforward then it won't cost a great deal. If it's not straightforward then you definitely need an engineer!

Anyway, even designing rebar for a simple footing needs a professional. There are too many variables to consider to provide much help here. What size of rebar? How many pieces and layers? Vertical and horizontal spacing? Ties? I'm sure your case is very simple but without a professional design nobody really knows.

 

[Canarywood1]

The reason your code official is backing off is because your project sounds rather non-prescriptive (use of LVLs). He probably doesn't want the liability associated with telling you what to do.

Exactly, it's called CYA (covering your A$$)

 

[crecore]

3 2x4s would be about 8-9k lb column depending on grade of wood but that's pure math, no safety factor whatsoever. I don't have my PE but I wouldn't sign off on that. Even 3 2x6s would be in the 13-14k lb range, still no significant safety factor.

Regarding the rebar, always use. In my footings I usually run verticals, then tie a horizontal rectangle to it, leaving the horizontals extending beyond the rectangle... Like a tic tac toe board. Dimensions vary by footing size.