aggregate for shop floor.....well....under the floor...

Starting plans for a new shop, setting up for 60x60 with intentions of expansion....

Any ways, what can a guy figure a yard of 304 (B19) weighs? Or say at 6" thick how far will a ton cover?

Planning on a 6" thick 4000# slab....what should I have under it?

I'm planning on a grid of rebar in the pour as well....

Thoughts?

This is my end all be all for the electric business, future expansion for farm shop. I'm 31, and want this done RIGHT so it lasts

I've always heard a ton/ cubic yard. Several inches of sand underneath, and maybe insulation if you live in a cold area.

While the density of crushed limestone will vary, 2,700#/yard can be used to estimate. That's about 20 cubic feet per ton, or 40 square feet per ton at 6" thick.

Good bedding for a slab will vary based on actual soil conditions under your slab. Talk to a local contractor at least to get some advice. If you really want it right, you need to get soil borings and have a soil engineer recommend a foundation. That's what industrial firms do, and they don't do it just to spend money. The engineer will also recommend rebar spacing, which will be less than you expect. I had an engineer design a slab for a shop with a 6" floor. He specified #3 four ft on center. We just couldn't go that light.

I always float a slab on sand with a vapor barrier on top of the sand. Sand self compacts when you wet it down, rock needs to be rolled to compact or you may see future settling. Sand is also generally cheaper but it needs to be clean fill sand as clay in it will cause swelling and shrinking.

What ever you use DO NOT SKIMP ON THIS ! I haul sand and stone for this very thing 3 times a week. 1st check your building codes they may have a requirement. 2nd What material is closer to the site. 3rd What is the drainage ? If its wet I would do stone if it's dry sand would be just fine as lo g as it will compact. If it says 6" put 10" for a base.

What we have always used is called "screenings". About 4-8" of that put down under the slab will work for even compaction and support. Screenings are very small chips that when wet or compacted can become has hard as concrete itself. Usually limestone around here, some granite. It's cheap, about $100 for a belly dump or 21 tons. And 21 tons will go along ways as far as area covered. We have about 8-16" of sand on my property, and when making our driveway we brought in 64 tons of it. At 6 inches deep and then compacted it has seated itself in the sand just fine and it's very hard. Hard enough a shovel won't dig into more than 1/2" or so.

My concrete finisher likes wire. He put down a 6 inch floor. Didn't use forms, used walls of pole barn. It was done in one continues pour. Nothing under floor. I purchased a self leveling dewalt rotating laser. my 30x50 slab cost $100 for each 1/4 inch. So get everything as level as possible to save money. My slab was put down on hard packed clay, nothing underneath. Hasn't moved, settled,cracked or moisture issues. Finisher came back the next day and cut lines in floor. I'm glad I hired a guy that makes his living finishing concrete. I also made sure water runs away form farm, not towards it. I did all the excavating before barn was built. Put it on the highest point, didn't bring in any fill.

If you put down 6in of stone which would be the min. it will take roughly 133 ton and about 77 yards of concrete. I would put a vapor barrier under concrete. Jim

To make sure the job is done right with that much $$$$ involved I'd hire a certified concrete inspector,won't cost that much really.They'll test your base for compaction required and most importantly make sure the concrete is in spec and poured correctly.I
worked in the concrete supply business for 25 years and can say easily 90%+ of the NON inspected concrete poured was out of spec with too much water in the mix (too high of a slump)
being the main problem.Also if the supplier and finisher know test cylinders are being made they'll mind their 'Ps and Qs'.

The subgrade needs to be firm and dry. We have a goetec check before ever putting gravel down. Then, 3/4 minus clean gravel (no silt in the gravel) compacted to 95% or you can "proof roll" with a loaded truck to see if you have any yield. The slab would be 6" thick with #5 rebar @ 32" o.c. In our case, this would be one pour so joints would be 30' o.c. each way. At the joints, the rebar is stopped and #4 x 24" smooth dowels greased are across the joint. The joints are cut (about 2" deep) as soon as it's finished - earlier the better except if to early the saw will pull aggregate up instead of cutting it. Couple photos of a building we just completed.

Its hard to say what the sub-layers are without knowing more from the site, but barring water or other soft or unsuitable conditions, a properly built pad under the slab is important. Same with the strength of the concrete mix, reinforcing etc. You can take test cylinders as they pour, get 4 cylinders, fill each one third at a time to the top, rod each third 25x before filling the next third. Screed the cylinder cleanly off the top. You would have to have a lab test them.

Ideally, the layers below the pad will be well drained and supporting under the compacted crusher run or other suitable well drained gravel that the pad is built with. 95% or better, it can be easily tested in 12" lifts with a troxler nuclear density meter. Testing company could provide that service. Not saying you need to, as its not likely done much for buildings like these, but you can measure compaction if it was necessary. If I had a substantial loan against the project, I would consider it if I suspected there would be problems with the site or material, what the heck... their fees are nothing compared to fixing a bad foundation after the fact. Consider fabric under the pad, drainage, vapor barrier, utilities, future uses - extra pipe/stub ups, conduit, sanitary,domestic water, pex for heating, anything you need to coordinate within or passing through, upward in the slab.

In practical terms, a good excavation outfit should be able to build a suitable pad. If there is decent ground underfoot, with suitable gravel/crusher run compacted with a big ole vibratory roller... most places around here that's all you need. Fabric in some situations, drainage too, strip the topsoil, fill with gravel and compact properly.

It is fun to see the cylinder breaks, I have to admit, just to see what they break at. 7 day, 14 day, 21 and 28 day is why there are 4 taken, each one should rise significantly in strength over that time span.

The below is a link to a bunch of different slab details, it might be helpful.
6

That pump operator and guy on hose look awful familar where you at Ferd

The 6 inches of compacted stone sounds fine for a shop floor. Lot of streets and roadways do not have that. The soil beneath the stone needs to be compacted as well, all organic matter removed and any soil type fill must be compacted. The rebar grid is the way to go, most wire ends up on the bottom of the slab doing absolutely no good. Poly under the slab will stop moisture migration. Think about laying Styrofoam beneath your slab and putting in pex in floor heat piping. Just something think about, once its done its to late to say I should'of done this. But as has been mentioned,get a computerized batch ticket from the batch and keep you wayer cement ratio at specification for 4000# concrete. gobble

(quoted from post at 18:41:39 02/23/16) To make sure the job is done right with that much $$$$ involved I'd hire a certified concrete inspector,won't cost that much really.They'll test your base for compaction required and most importantly make sure the concrete is in spec and poured correctly.I
worked in the concrete supply business for 25 years and can say easily 90%+ of the NON inspected concrete poured was out of spec with too much water in the mix (too high of a slump)
being the main problem.Also if the supplier and finisher know test cylinders are being made they'll mind their 'Ps and Qs'.

Click to expand...

The one thing I learned for sure in college was limiting the water in concrete. We had to mix our own concrete and make small concrete beams. Four different water amounts. The wet-est looked real good. The driest I could hardly pack into the beam form. Couldn't get a good finish on the top. Then three weeks later we each got to break our own beams. I was astounded how much stronger the dry mixture was. Strength went right down with the increase of water. So in the last fifty years I have poured concrete just as dry as I could work it. If you don't have to vibrate it, it is too wet to gain the strength it could have.

Paying the extra for 4,000# mix makes the mud much more workable and the surface will finish off really nice.

Styrofoam, the white stuff, will not support the weight. You need to use Polystyrene under concrete slabs. I once put up a building with heat in the floor and the specs were non specific as to insulation under the floor so I called Dupont, spoke with one of their scientists and he told me Polystyrene, the stuff that snaps when you bend it .

Well first the you need to remove any top soil from the area your wanting to build on. It will NOT compact as well as clay or gravel.

Second you need to make sure the area under the slab drains. This can be done by grade only or with drainage tile runs under the floor. (My newer shop has compacted clay with drainage runs on 20 foot centers under the fill.

Third. Six inches of fill/gravel is the MINIMUM I would want under a shop floor. Even then the dirt/clay under would have to be well drained and compacted. ( my shop had six inches of 1 inch stoned compacted with six inches of 304 or 3/4 crusher run compacted on top of the base.

Forth: You need a vapor barrier under the concrete. If your going to heat your shop insulation should be under the concrete too.

Fifth: #4000 mix is not really strong enough for a shop floor if you ever plan on lifting heavy loads in small area. Meaning a hydraulic jack directly on the floor. A good friend poured a six inch shop floor with #4000 mix. He pulled a loaded semi in to change a tire. He set a 20 ton jack right on the floor. He raised the truck fine. He also cracked the floor where the jack was setting too. Also if you ever are thinking about a car lift or floor mounted jib crane then the #4000 mix is not good enough for that. All the shop floors I have poured have been #5000 mix. I also used rebar every foot on center and the last shop has rebar and fiber bond in the concrete.


Some things to think on. Going from #4000 mix to #5000 mix will cost about $10 per yard of concrete. The #5000 mix ix 20% stronger than the #4000 mix. REBAR is CHEAP!!! So use plenty of it. Your only going to be doing this once. The extra cost of doing it right wouldn't be more than 10% higher than doing it wrong/cheap. So figure the extra cost over the life of the building. It is a very few dollars per year. I have never heard anyone say they wished they had poured their floor thinner/weaker/poorly drained.

Far be it from me to dampen your enthusiasm....but...

No matter what you do to that slab...it's gonna crack.
No matter how you set posts...they gonna rot.
No matter how well you build the roof...it will eventually leak.

Only the very young think they are building something that is going to last. Put up the best you can and be grateful, at 31, that you will have time to repair and improve upon it. Happy building!

I have a 40 x 60 shop. I took a 3 point post hole digger and poured 30 piers then poured my shop floor. The piers were even with the bottom of the floor. Then I put rebar on 2 ft centers both ways. four inches of 5000 concrete. I would NEVER put down fiber concrete. We poured a lot of it in outside storage areas where I worked and it was not worth crap.