Rigid metal frame 50x100 building considerations

[5030tinkerer]

I just picked up a de-constructed 50x100 rigid metal frame building. The plans call for a continuous footing. In my area, that means the bottom of the footing 42" deep.

Any ideas on what sort of footing and frost wall I will need? Would the wall tie into my (hopefully) future concrete slab or would the slab just float inside the building?

I was thinking about having the frost wall extend 15" above grade so that the planned 5" slab with 2" of rigid foam underneath would leave me with 8" concrete curbs.

Any and all thoughts are most appreciated. I am also considering stacked concrete block filled with concrete and reinforced with rebar since I don't own any concrete forms. Crazy?

 

[mattellis2]

i'd pay an engineer to design a proper foundation for you. metal building foundation sizes are usually driven by wind uplift forces. you need to make sure you have enough concrete to provide ballast with an appropriate safety factor to resist the uplift that is going to be developed.

also, if footings have to bear at -42" to avoid frost heave in your area, you're going to need a pretty substantial amount of rebar, just to meet the minimal code required cross sectional areas.

-matt

 

[CATMAN]

I really can't help much, but I did want to mention, that when my Dad built a 60x75 Bulter Farmstead metal building, years ago, they actually dug a trench between the major support columns and tied them together between the 60 foot width(underground) with cables. This may be a common practice, but I thought I would mention it.

 

[5030tinkerer]

I appreciate the mention on upforce requirements - I hadn't thought of that and will heed the advice. Still, if anyone has already been down this road, I'd love to hear what you were told.

The locals tend to use rebar tied together in trench and then set in concrete between the major support posts, set about 12" below grade. I'm not sure why that is magically not subject to frost heave, though. I really like the idea of cables taking care of this.

I may dig a trench at footing level and just connect things up both at the top and the bottom. Thoughts?

 

[Cat_Driver]

Put up a 100'x125' but I went with a 100% cement slab. The beams are held in place with bolts set in the concrete. All the walls are further strengthened / squared up with cables and turn buckles.

If my memory serves me right the contractor set all the footings holes first and then did a one pour for the slab and footings all at once. 30' x 100" of the building was set for future so I have no building on that part of the slab, just the bolts still popping up from the slab.

No matter what, I think you will need to have an engineer involved with proper stamps per your local codes.

 

[5030tinkerer]

Interesting that your building was able to simply have posts. At its last building site, there was a perimeter frost wall around the entire perimeter. If I could get away without that, using 2' or whatever diameter holes 48" down instead, the money saved in trenching and frost walls could easily go against a slab. I would love to have the whole interior benefit from a slab, but had been concerned about the ability to financially swing it.

The monolithic pour of a 5" 4000psi slab (especially if I opted for a thickened edge) and piers would hold the posts nicely, I would think.

 

[john4153]

I put up a rigid frame building in southestern, MN. Its foundation was called a "grade beam" with footers. It was 60X50 deep (i.e., each section was 25 deep and there were 6 footers plus footers (2) for the door. Between the footers was a grade beam only about 1 foot deep. The slab was poured with the footers and grade beam. There were no real problems with it (I kept it heated), but a large indoor tennis club in the area was done similarly, except the main slab had an expansion jount all around and between it and the grade beam. It was truly floating and would be something to consider. After almost 30 years, the floor in my building has no new cracks (one appeared in the first year near the door opening). A floating slab may have avoided that crack.

John

 

[5030tinkerer]

I don't plan to keep this building heated except when in use. I like the idea of a floating slab, but am concerned that I need to tie the posts to each other. One way to do this would be to go ahead with the aforementioned cables and then let the slab float just anyway, but am curious if there are better methods.

 

[john4153]

Of course the posts are tied together. There is rebar in the grade beam, and above ground, you have the metal siding and "wind" bracing (i.e., crossing bracing). In my building with only 2 sections, only one section needs to be cross braced.

John

 

[Duffster]

Is this a clear span?

I think floating slab is good idea, economically, just realize that it is not perfect and expect to have a wild crack or door that doesn't work perfect in the winter.