Floor stone prep and 12'x12' concrete apron

[JeffsJeeps]

Hello all!

I've been searching and reading up on other's Q&A about concrete preparations. Many great ideas shared/posted, and still I have a few questions and concerns as I am about ready to have my 30'x32' floor poured prior to the apron.

The fill that's under the barn is solid. I can't dig for a bush without using a machine! That being said, can i get an agreement that 2-3 inches of 3/4" clean crushed stone is ideal for a 5" pour?

As much as i would like to do the PEX and radiant, I am NOT digging down again to accommodate the foam board, etc. You see, the one regret i have for this building was that the man door/skirt board should have been about 6 inches higher. I really wish i had known the consequences of not being high enough. As i know now, it's much easier to add material than to remove it.

I'd like some thoughts for how i want to do the entry slope from the apron into the garage. I have split sliding doors (two 7'x10') for a 14' wide entrance. The idea is to have the entire floor level, and to form a pitched slope of about 3 inch rise, from the apron to the garage level over 2-3 feet of length. If the entire floor is machined smooth, and this slope is broomed, how do you think that'll work out? Should look sharp (IMO)! I need the bottom of the slope to be about an inch above the back of my sliding doors to give them something to ride against and prevent blowing in.

My other issue is this apron. I need to get photos up, but just go along for now... My over-zealous buddy graciously used his mini excavator and dug a hole. A hole about 18 inches deep, 14' wide and 16' long. Why? I am still trying to figure it out. In that hole was a really big rock that needed to be downsized, and also a big stump/root system that had to be gone also. This apron pit has pushed me back two months of time, and almost $1,000 in stone. I can share details later how i tackled the rock and root.

How much stone is too much for under an outdoor, six inch thick slab measuring 12'x12'? Assuming it's the correct stone and plate-vibrated in 3 inch increments. I've got about 4 inches compacted but need another 8-10" prior to setting the forms for the pour (after the barn floor pour NEXT WEEKEND)!!

Thanks,,
Jeff

 

[matt_i]

Personally I'd pour a level slab, the slope in one pre existing shop drives me nuts.

One could pour concrete directly on the ground if the base is solid enough.

If you want to fill a hole, "dirt" is a lot cheaper than buying stone. One can usually find fill dirt for free if looking around a bit. Of course compacting it is more variable. Can you fill and compact "dirt" but then wait a year for mother nature to do some natural additions to the compaction? That would give a greater confidence that its all ready to go.

 

[ConCretin]

If your 'fill' appears to be well compacted and granular (as opposed to cohesive such as silt or clay), it should be fine to place on. There is no reason to dig any out just to add stone. The concrete doesn't care what it is placed on as long as it's able to provide uniform support.

I'm not sure I understand the reason for the sloped section at the door but your proposed detail sounds fine to me.

With regard to the stone under your apron, place as much as you need. Theoretically, stone doesn't need to be mechanically compacted but it can't hurt to run a compactor over it a couple times while you are bringing the grade up.

Give my Guide to Floor Slabs a read for some additional thoughts on the whole process. Good luck with your placement!

 

[JeffsJeeps]

I've read the SLAB GUIDE a few times and get a lot out of it. I also encourage everyone to read it.
I'll agree that filling a hole with dirt is fine, however i have spread that dirt out to other parts of the yard already. My solution is to go with this RECYCLED CONCRETE AGGREGATE. The biggest stone in it is about 3/4" and it has the fines in it. It's great for compaction and is a third the price of stone.
My concern is whether the moisture that will accumulate and freeze within the fines of this RCA or a Quarry Process QP could cause a concrete pad to lift or crack? Assuming drainage is good, there is still potential for water&ice to get into those compacted fines vs. the clean crushed 3/4" stone.

 

[matt_i]

My personal take on the fines is they pack, hard by mechanical compaction means. But then as time goes by the fines filter down and the base isn't as well compacted. As opposed to the washed stone which compacts once and then there's really nothing that can move. If one had the time (a year) to let mother nature assist with washing the fines down then this would be a very good base, and you could still drive on it with the exception of some ramps.

I question pouring 6" thick exterior flatwork unless you have heavy trucks. Like medium duty trucks.

 

[JeffsJeeps]

I'm going to have 3/4" clean crushed delivered today. The tandem will dump into the pad pit. Today we hand raked the leftover Dense Grade Aggregate over the bottom course of 1.5" crushed rock and plate compacted it down.
For visual purposes i set strings to show the top of concrete. I've got a good foot to come up. Six inch of stone and six inch of concrete. I don't want to worry about a 9000 lb vehicle setting on jack stands. I also envision wrapping around this 11x14 concrete pad, the full width of the building with blacktop.
I would love to have a COMPASS ROSE stamped in to this pad. I'm going to call some stamping contractors and see how far i would have to bend over for that request!