Best concrete floor prep for pole barn on downward slope

[jaxs]

You've received advice on getting ready for concrete so I'll give you some about making the concrete last. If your soil shrink's as it dry's then swell's when wet,managing rain runoff is very important. The indication is if it pull's away from foundations or soil cracks when dry. Ideally,moisture remains' close to same as soil 10' from building season to season. At minimum,wide fluctuations in moisture in short period is to be avoided. This may require a berm uphill to divert runoff and gutters on building leading to ground gutters or underground drains.

 

[Cord]

Well, it seems that at least this has a unanimous vote... Still not sure I understand it since I would think 10 ton of gravel on top of it with 4-5 in of concrete as well would kill the grass and compress the topsoil after tamping and a couple of weeks of settling, but that's why I'm not the expert. :confused3:

I plan on getting in touch with someone today to take a look at it tomorrow who I believe has a bobcat and could remove the topsoil and haul in the crusher run to build it up to be ready for concrete,

So, what is the opinion for putting plastic between the gravel and concrete? I have seen arguments both ways on this...

The problem is the organic materials found in topsoil moves and thus provides poor support for the materials above it. You build a base from the bottom up. It doesn't matter what you have on top when your base is bad. To that effect; don't cheat your compaction. You'll want 90% or better which is hard to achieve. Generally you are there when a pad foot compactor "Walks out" and rides on top of the surface. Because you didn't build a pad for the building you will have cracking issues at the walls where the base wasn't fully compacted. Rebar will help with this, but only if they are placed on stands. Placing rebar on the ground is a waste of good money.

To place a vapor barrier down first is easier than trying to add it later. 6+ mil poly would be sufficient for a building like this.

 

[dickfoster]

3/8" Pea gravel is good for underfill as it self compacts about 90% at least. Or crushed gravel if you can't get the pea. If you've got concrete rubble you can toss that in there too then fill with pea gravel. Anything that won't compress, rot etc. Just nothing organic.

 

[neopheous]

Fellas, a lot of good advice and I appreciate it. My thoughts right now is to just to install gravel (after sod is removed) probably will use 304 crusher run. My plan is to build it up to within 4-5 inches of what would be then be the top of the slab. I may leave it just gravel until later this fall so that it has time to settle after having Implements and tractor on it.

My questions now are more concerned with how to do the skirting while filling it with gravel. Should I go ahead and close the bottom in with more treated lumber or just let it free flow from the inside out? That way gravel coming outside the edge of the building where there a gap between ground and the bottom of the skirt. Or could I just use the sod and topsoil I remove from the inside and stack it outside to fill those gaps? I do plan to put gutters on and direct the flow to the creek nearby.

Also has anyone used their tractor to remove the topsoil inside a building like this? I looked at t today and I believe I could maneuver it inside the building well enough to clean out 90-95%. Wouldn’t be as efficient as using a skid steer but I would have to rent it or have someone else do it. I have a Kioti CK4010. Could possibly even use the backhoe to rake out the 3-4 inches of topsoil needed to be removed.

 

[Streetcar]

If you use lumber to contain gravel you will have problems eventually, let gravel spill out.
Excavation in a building is hard. With tractotor you will have lots of hand work

 

[neopheous]

If you use lumber to contain gravel you will have problems eventually, let gravel spill out.
Excavation in a building is hard. With tractotor you will have lots of hand work

Thx that’s good to know. So no containment and Maybe it’s back to getting a skid steer in there to get it done.

 

[dragoneggs]

If you use lumber to contain gravel you will have problems eventually, let gravel spill out.
Excavation in a building is hard. With tractotor you will have lots of hand work

Agree here... let the gravel spill out. How deep is the organic rich soil under the sod?

 

[Tractor Seabee]

3/8" Pea gravel is good for underfill as it self compacts about 90% at least. Or crushed gravel if you can't get the pea. If you've got concrete rubble you can toss that in there too then fill with pea gravel. Anything that won't compress, rot etc. Just nothing organic.

Pea gravel is a no-no under a slab. It rolls around like marbles and works its way into the subgrade when under compression. Pea gravel is a good fill when there is a solid contraint for it to push against like a foundation stem wall. It will not compact as you keep pressing it out and down. When you walk on it or drop concrete like out of a pump hose it moves around and gets brought up into the concrete.

DO NOT let them move the concrete around or try to consolidate the concrete with a vibrator; there are proper tools and equipment for that.

Crushed gravel is the only base that will compact. It should have crusher fines that is why it is called like 3/4 minus; the minus is the smaller gravel and the crusher fines, that way it all keys together and provides a solid mass that will not move.
Don't put junk in it as it will probably create voids.

The OP's problem with filling the slope is also an easy fix if you use crushed gravel. Just extend the compacted gravel past the walls a couple feet at the same height as the interior. Lesson learned: Prepare the subgrade (at least to rough dimensions) before building or better do the slab first while it is easy.

Organics in the fill: Problem is they continue to decompose over time and shrink. That causes cracks and differential settlement as the slab continues to compress the base material. The real experts excavate all top soil till the color gets lighter. An ounce of prevention is worth a pound of cure. Remember it is your slab not the contractor's. That is always the problem when you do not provide a specification for the contractor to bid on. That is why prices are usually all over the place and you wind up with the gypo outfit.

I have made my living in the construction world for 65 years, seen it all; MAYBE!! New stuff every day

Ron

 

[neopheous]

Agree here... let the gravel spill out. How deep is the organic rich soil under the sod?

A LOT of clay in the area so I’m guessing no more that 3-4”. On the one side of the building maybe less as I had a trac hoe take some of prior to building the building.

 

[neopheous]

Pea gravel is a no-no under a slab. It rolls around like marbles and works its way into the subgrade when under compression. Pea gravel is a good fill when there is a solid contraint for it to push against like a foundation stem wall. It will not compact as you keep pressing it out and down. When you walk on it or drop concrete like out of a pump hose it moves around and gets brought up into the concrete.

DO NOT let them move the concrete around or try to consolidate the concrete with a vibrator; there are proper tools and equipment for that.

Crushed gravel is the only base that will compact. It should have crusher fines that is why it is called like 3/4 minus; the minus is the smaller gravel and the crusher fines, that way it all keys together and provides a solid mass that will not move.
Don't put junk in it as it will probably create voids.

The OP's problem with filling the slope is also an easy fix if you use crushed gravel. Just extend the compacted gravel past the walls a couple feet at the same height as the interior. Lesson learned: Prepare the subgrade (at least to rough dimensions) before building or better do the slab first while it is easy.

Organics in the fill: Problem is they continue to decompose over time and shrink. That causes cracks and differential settlement as the slab continues to compress the base material. The real experts excavate all top soil till the color gets lighter. An ounce of prevention is worth a pound of cure. Remember it is your slab not the contractor's. That is always the problem when you do not provide a specification for the contractor to bid on. That is why prices are usually all over the place and you wind up with the gypo outfit.

I have made my living in the construction world for 65 years, seen it all; MAYBE!! New stuff every day

Ron

Yeah, I’m going to use 304 crusher run to fill. I agree that I’d have rather had the slab down first but the Amish that built the building said they wanted it down after, the concrete guy wanted the slab first. I understand that as it causes issue for one or the other unless you plan on building on top of the slab, which I did not. I can see digging the post holes would have presented an issue if you had to do the right next to the slab, unless u dug then by hand.

As I measure it I’ll only need to place gravel about 1-1/2-2” up on the first 2x8 on the bottom to allow room for the 4-5” of concrete on top. Not sure how much gravel it’s going to take but I would imagine between 30-40 tons.