Backfilling pole barn, need advice

[deezler]

I just poured my rat wall first, THEN leveled and compacted the entire barn interior for the main slab. I set my rat wall top height to the exact level of the bottom of the slab, so the slab pour could just go right atop the rat wall.

If you have good compactable material, you should be able to compact the middle area and have a deeper thickened edge zone compacted also. But you could always use some scrap wood to make a crude form also, holding the main middle area together for compaction.

Question, why do you feel you need a thickened edge slab? If you pour 4-5" thick or more, with #2 rebar on 2x2' grids, your slab will be very strong and a thickened edge wont really do anything extra for you (except take more prep work and cost more in concrete). Just my opinion. Also recommend adding fiber to the mix, typically only $7/yard more. And plan on cutting control joints 1/4 to 1/3 of the way through your slab thickness on a 10x10' grid the day after your pour. This keeps the cracks (all concrete cracks) exactly where you want them, and nowhere else.

 

[DrewStyduhar]

Good morning,

You're in Michigan, I think I remember reading how rat walls are required up there? Did you just use an inner form and pour between the posts?

Not that I think my extra skirt work was a waste of time but after talking to the local folks here I'm getting mixed responses about how long the wood/foam will last in the ground. With a flat slab, Ill need almost 9" of fill. Although I have my own opinions about the longevity of the skirting, someone local asked me what my plan is if the perimeter foam fails......falls apart or gets eaten up or whatever? Or if I ever have to remove a bottom skirt board for any reason, am I confident the fill will be contained or will I lose slab stability? Im not sure how the grading guys will be able to compact the fill BETWEEN the posts. I think those are solid questions and I guess my thinking was a thickened edge slab or rat wall would help capture and isolate the fill from the bottom skirt in the event there is ever an issue with the buried skirting in the future.

thanks,

Drew

 

[deezler]

I don't know if rat walls were technically required, but I wanted one anyway, to keep critters out from beneath my slab. I am positive I would have a family of skunks, groundhogs, or rabbits living under my slab if I didn't do it. When I mentioned it to my local township inspector, he nodded approvingly, but I didn't clarify if it was actually a requirement.

I don't get why you really care how long the wood or foam will last in the ground. It might rot, but it won't just vaporize into thin air. Aren't you going to backfill on the outside of the barn also? If you have earth on the outside of the building, then nothing will spill out from under your slab in the event of woot or foam rot. In any case, a well supported slab with proper rebar in it isn't going to fall apart if only the very edges become unsupported.

I don't have very good pics or my ratwall process, still had an old iPhone back then. I forgot that I didn't dig precisely between the posts, and elected to run my ratwall mostly inside the posts. I think this was because the digging was just too annoying, and I had an excavator on hand, so I could easily dig inside the posts. I think I was also somewhat nervous about fully de-stabilizing the posts.

But on the other side I did navigate between the posts some, and bump the ratwall out (into the building interior) around the posts).

Then I compacted the crap out of my sandy soil subgrade before foam board, vapor barrier, pex tubing and rebar install. Notice the extra foam board strips atop the rat wall, inside the skirt board, to insulate the exterior of the main slab edge (important!)

More pics of the slab prep available if you want to see.

 

[DrewStyduhar]

Maybe a dumb question here but we have skunks, ground hogs and everything down here in NC. Hell, we shoot groundhogs from the dining room window . Sure, it doesn't get as cold as you guys but why is it more of an issue with them burrowing under slabs up where you're at? Nobody around here even knows what the hell a rat wall is. I should take more pictures of the back of my barn, I have about 3 feet of fill in the back that blends down to grade over a 10 foot run. Looks like a perfect spot for something to dig in.

Oh yeah and about rebar....the concrete guys are here are super lazy. Its fiber and that's it unless its a code required footing. I talked to three different concrete guys and they thought I was crazy for wanting to add metal. You know the mentality....easier and faster = better.

Drew

 

[DrewStyduhar]

Here's another one for ya guys. Regarding termites, do you think filling up the building with sandrock or crusher run would help keep those guys from setting up shop under a cold slab? I have seen where ants or whatever are burrowing through sandrock they used on my pad even though its compacted well. Never seen anything burrow through the crusher base we have on our driveway. Maybe it doesnt matter but figured I would ask. Leaning towards crusher over sandrock with a skim of 57 on top.

thanks,

Drew

 

[Juiced06GTO]

Check out my guild thread over on GJ. I dealt w pretty much the same issues you did. Maybe something in there would be helpful!

Finally building the shop!!

 

[Thunder chicken]

Nice build Juice!! Thanks for sharing!

Drew, I’m getting ready to pour a slab inside my pole building as well and had some of the same bought you’ve had.
Sorry not a great pic but you can see I ‘boxed’ (3sided) around the bottom of the posts with pwf. The top of the lumber will be top of the slab. The pocket between the skirts as you fall them is insulated with foam, to insulate the slab edge with about R20. Outside i did like you and used metal flashing. It’s nailed on with roofing nails and goes below the skirt board a few inches into my sandy soil/fill.
I’ll insulate the slab with 4” of eps foam. I’m in a cold zone.
Gotta figure out how to insulate the 12’ wide door opening edge of the slab yet, lots of info and debating with a google search.
I watched some videos from RR Buildings on u tube, and used some of his ideas in my construction.

 

[Juiced06GTO]

I used angle iron to form a threshold for my garage door, I then insulated the inside of the threshold with foam. I could only do inch thick foam there, but am hoping it is enough of a thermal break to keep most of the heat in.

 

[DrewStyduhar]

Hey guys, been a while.

Long story short I have been blown off by 4 or so dirt guys to help me with the fill work. Had 100 tons of crusher delivered and another 20 of #57. Also had 4 quad axle loads of cheap dirt for outside of barn dumped off. You guys are gonna roll your eyes at this but I decided to move forward pouring the rat walls I previously talked about, haha. My wife said it was a sign that these guys kept blowing me off and just knock it out. We had a warm spell last week and I have all walls finished except five but plan to be done this week. 21 bays total in this barn. Each bay took a little more than (3) 80lb bags and its been pretty exhausting prepping and mixing and pouring and troweling and all that jazz by myself but its almost done!

Here is what I did:

- Set up my rotary laser to mark the top of the future concrete
- Measured down 5" and marked a line on post since I plan on going with 5" concrete.
- Measured down 2 more inches and made another mark on post since I'm going with 2" of foam or at least allow option to
- Recompacted and smoothed sandrock between each post with hand tamper
- Ripped 1.5" thick foam with 45 degree beveled top and attached to skirt using deck screw and fender washers
- Cut 6mil plastic and laid up against the foam and down and out
- Cut a **** ton of 3/8" rebar @ 16" and 18" inch length and pounded down 3 per bay with tops ~1.5" below future concrete surface
- Used 2x8 or 2x10 ripped down for form boards.

I apologize for the horrible pics (phone camera is barely working) but shows the sort of work I'm finishing up.

thanks,

Drew

 

[Midniteoyl]

Nice. Looking good