Footers under concrete floor

[wmonroe]

I am going to be pouring the concrete floor in my 40' x 60' building this spring and am thinking about putting small footers in for a possible future loft/mezzanine/storage area. My thought is after the floor is done install 6x6 posts against the building posts and then also 10' out. I would tie the posts against the outside wall to the buildings posts just for lateral support but not for vertical load carrying support. I was planning to have a small footer under all the proposed post locations with the footer being approx 18" square and 8" deep and then there would be the 5.5" floor above that. This would all be done in one pour so the floor and footers would be all one piece.

Has anyone done anything similar to this or see flaws that would need addressed?

Thanks

 

[Shocker]

How thick is the slab you are going to have poured?

My dad's shop is smaller, but he did the same thing are you are proposing. He just glued and did side bolting to the 6x6 posts to a 6" concrete slab at 10 feet out.

He tied a ledger board to the exterior wall supported by 4x4's along each 8x8 support post (his is a pole style barn).

So in short, I am not sure it is necessary to pour footings for the posts.

 

[wmonroe]

Floor is going to be 5.5" thick. Originally I was going to tie a ledger board into the outside posts but figured for the minimal extra investment I would add extra posts to support the load. My thought is to have the loft structure basically self supported.

 

[ChargedUp!]

During the build of our new home and garage, there are a few extra footers added. There is one at the stair section, another for a 6x6 post at the basement and finally a large 2'x2' footer in my garage. The builder thought that one important due to the size of the garage floor. They are full depth footers too btw.

 

[805gregg]

8" isn't deep enough, go at least 18" with rebar, or contact the architect

 

[Nowater]

The center pier in my garage is about 6 feet square and two feet deep. It is not to hold up the garage (one-half the roof rests on this column) it is to hold it down during a hurricane.

You really did not say what kind of load you are putting on this post, but at a rate of $100 a cubic yard, an extra cubic foot of concrete costs you less than four dollars. This is not the time to save a few cents, IMHO.

 

[ConCretin]

Thickening slabs on grade where future point loads will be applied is quite common. I would suggest however that the load imposed by a few posts for a loft will not exceed the capacity of a 5.5" slab so it's probably not necessary. With that said, I'd probably thicken the slab to 12" or so since the cost is negligible and peace of mind isn't.

 

[BWS]

Deep subject....one that has several "attempts" to resolve.

Obviously with proper planning,droppin in point load piers at the time of the original pour is pretty painless.I'd suggest not making sharp angles though....IOWs,don't just dig a 18 inch square hole that comes up to a 90* right at the bttm of slab.Bevel the "walls" of the footer/pier a little and soften the "rim" where it ties into slab*.

Another concern is whether its a "mono" pour or a treated as two seperate pours.IOW,s,you pour piers first...coming back and pouring floor later.This would be done at the time you're pouring the building's perimiter footers.

One more idea is...and it ain't a very popular one....is to say F**k it,pour floor,and then when all's said and done you come back and cut pier holes and pour them.Think about "why" D.O.T. will pave a new rd....then two weeks later come back and cut access holes for underground utilities?Yes,theres some differences in that and what goes on inside a building.....Just sain,with proper equip,and relatively "soft" concrete.....sometimes this is a bonafied solution?

*Stress risers in concrete ranks as a major reason for cracking.....theres other's,but this is a consideration.Just avoid sharp anything in concrete.....soften up the edges.

 

[wssix99]

This would all be done in one pour so the floor and footers would be all one piece.

I'd separate them from the beginning. The floor will be on fill/softer gound and can move slightly while the footers won't. You could end up with cracks around the footers. IMO - better to have control over that and use an expansion joint.

 

[johonmirae]

They are full depth footers too btw.

 

[wmonroe]

Thanks for all the responses! To answers a few points that were brought up. I could easily pour the footer pads prior to the floor and agree that would probably be the better way to do it. Not sure that I need a 18" deep footer as the building is only sitting on 18" circular by 6-8" thick pads and I'm sure the loft won't have more weight than my 40x60 building. The main use for the loft will be basic storage: power tools, truck/tractor filters, oils, etc. the heavy items will remain on the main floor.

Appreciate the suggestions, keep them coming.

 

[wmonroe]

They are full depth footers too btw.

I can't see your picture, not sure if it's me or not.

 

[ScottinSSMd]

From what I have read, you are doing/have a pole building and putting a slab within this structure already built. Since you say the slab is only going to be 6-8". If this slab is independent from the pole structure (floating) then I wouldn't put footers in for a future loft. I would cut holes and post down through the concrete with your poles to tie into structure. If you put your loft on top of the slab, it will move differently than the structure, causing stress cracks, etc. The slab should float as it is intended to do.

Also, you are in a deeper footer frost line than here in DC at 24-30" Not sure how you can get away not being at least 24" to the bottom of your footings.

Good luck and post some pics.

 

[wssix99]

Not sure that I need a 18" deep footer as the building is only sitting on 18" circular by 6-8" thick pads and I'm sure the loft won't have more weight than my 40x60 building.

I'd be more worried about frost heave, especially in PA. Your foundations only go down 18"?

 

[NUTTSGT]

Before I poured the apron in front of the garage, I used a post hole digger and poured three columns. I used some rebar and reinforcing wire inside each one. Over kill maybe but it gave me peace of mind for some cheap materials.
Columns that went in the holes.

Holes with columns inside the concret tubes.

4x6 porch post sitting on concrete column.