New Build - Foundation or Fill?

[dcase84]

I'm getting ready to put up a 30'x40' post frame building.

Due to local politics, this is the only portion of my property that I will be able to build my planned shop. (Without rezoning, survey, paperwork, delays, etc...)

In the pictures, the shop will extend from the front of the mower deck all the way to where it slopes up again in the back, and three feet offset from the field on the left side.

As you can see in the pictures, the site is currently sloped. The most significant would require approximately 3' of fill to bring it to grade. What does everyone suggest for footer/footings? Would fill and slab be sufficient, or am I in poured wall/block foundation territory?

 

[Daniel Dudley]

If I were stick building, I would pour a foundation, and fill the inside. If I were building a pole barn, I would just fill and put a slab in later.

When I did my garage, I did fill in and level out a three foot slope, and poured a slab over it. I used high drainage road bed gravel. It worked out for me, but it has to be done correctly. That was 15 years ago. When I did the shed addition (22x26), I built it as a pole barn, and put gravel in later. Poured the slab a few years after that.

Talk to some builders. Get an engineer. I did neither when I built my garage, but I had been building for 20 years when I started it. Like most things, it isn't what you do, but how you do it that makes the difference.

 

[ozyborn]

I would say chat with an engineer on this. But the most important thing is you have an inspector. Like the great one you have watching in the 3rd photo.

 

[kbs2244]

Typically, with pole construction, they put in the poles without regard to the slope.
They just use longer poles at the down hill wall.

Then they use treated timbers to build a wall inside the posts, using them as support.
Use drain tiles at the bottom through the lower layer of the wall.

Then fill with coarse rock for god drainage and pour the slab on the fill.

 

[dcase84]

Thanks guys, I feel a little better. I searched before posting and it was all doom and gloom.

I will definitely be going post frame construction, and I'm now waiting for a couple engineers to take a look. Since I have the equipment I plan to handle most of the prep myself, and due to a fear of heights I'll end up having a crew put the building itself up.

Somehow that dog magically appears, I can spend five minutes calling her, only to realize she's standing right next to me.

 

[Novicaine]

I once built a standard framed 30x40 shop with a block foundation on the side of hill, worked great to handle the slope. I then filled the inside with essentially packed lime. A little pricey, but no regrets.

Then at my next house, I built a 40x50 pole barn and used packed road rock to bring the floor up to level, but it was less of a slope, maybe a 2-3 feet drop on the lowest side. Then I poured a slab. Now I have regrets... I really wish I had taken the time for a proper foundation.

My main gripe is outside the building I now have these piles of gravel that extend a few feet out and the exposed wood framing at the level of the concrete. Had I put in a proper pre-poured foundation of some sort, I'd just have a 2-3' vertical wall there.

 

[Highbeam]

I built my 30x60 poles barn on a slight slope, needed about 30" of fill at the far end, sort of a cheese wedge shape. I filled with imported soil and rented a huge vibratory roller two or three times to beat the fill down after each 6" lift. The poles go down through the fill and well into native soil so the building doesn't know it is on fill. The slab is what you need to worry about.

Strip the existing sod and topsoil, compact the native ground, lay in 6" of fill, compact, additional 6" layers with compaction between to grade, and then drill your holes, build your building, plate compact like mad, crushed rock subgrade beneath slab, compact like mad. Now you're ready for your slab.

Oh one more thing. The filled area must extend well beyond the building, like 10 feet in all directions and then a gentle slope to grade.

 

[Diesel Dan]

As stated proper compaction of the fill is a must.

 

[rancherbill]

I would say chat with an engineer on this.

As stated proper compaction of the fill is a must.

I would use fill that is properly compacted. Compaction is doing the steps correctly, it is more than just vibrating a little bit. Get some advice. You reasonably can achieve 98% compaction, but that still means the down side will settle approx 3/4'.

The site PLUS the slope away needs to be compacted before the building is built. The poles on the down side need to be longer to get to undisturbed soil.