The Stovebolt Site Forums The Shop Area The Tool Chest Workshops and Garages Concrete floor questions

I'm finally on the verge of adding a 20x40 front porch/shed to the shop. While I've been around a lot of concrete work, I'm not the guy with answers, I'm more the ask questions guy. So, that out of the way, the east end of the 40' long slab requires a cut of about 4". The ground is fairly level toward the west end until the last 10' where it needs 1' of fill at the end of the slab.

The ground is high, solid and well drained. I'll most likely have the fill hauled in and the choice is fine sand or fill dirt. Any suggestions?

Another question, I'm debating welding up anchor plates with 4, 3/4" bolts for each of the 6 shed roof support posts. These anchor points would be set in the concrete. Or, I do have a hammer drill, I could just use redhead anchor bolts.

And lastly, I'm considering 4" of 3000 psi concrete. We don't have a frost line issue here, but I'm thinking since the 8" dia. pipe columns will set on the edge of the slab, I should pore a footer of ??? dimensions or at least pore a 1' sq. x 1' deep pier under each column?

I'll likely do the foundation work and set the forms and hire the rest out.

Any help with either of the 3 questions is greatly appreciated.

RonR

Your fill should probably be more gravel or coarse sand. As far as footings for the edge of the slab, just thicken the slab to 8" to a foot deep. Or you could use a separate footer of the dimensions you mentioned. A thicker slab at the edge where you'll drive off will help prevent it from cracking. You could ask some "hypothetical" questions for a "friend" of the building department in the nearest city.

Talk to the building inspector. They are public service employees and are there to serve you.

Thickened edge slabs are not approved here, but they may be OK where you are. 16" wide spread footings with 8" foundation wall are required here. We also need perimeter drains, steel mesh in the slab and compacted gravel sub base.

I got a permit and was glad I did. [censored] neighbour didn't like my new project and called the building inspector. No problem; all was in order. Haven't spoken to her for over 10 years now.

Thanks for the input guys. Fact is in our rural State, unincorporated areas or in the country, we don't have building inspectors. National building codes are of course in play, but if building without financing (which could trigger stamped plans) you can build whatever, however you want. My goal is to have a concrete floor for the shops roofed, open sided, front porch that'll stand up to light vehicles and perhaps a load of square hay (less than 10,000 lbs in an emergency).

Like Gord said, definitely use reinforcing in the slab. Wire mesh at a minimum. Since it'll be open to the weather, you don't want it to crack. Even though you're in Arkansas, you'll get freezing temperatures at times which will open any cracks and make them much worse, and will expose the reinforcing to corrosion. Basically, you're building a concrete driveway, but with a roof. Reinforcing wire and thickened edges are cheap insurance.

Ask what grade of concrete they plan to pour
And research what they say they can deliver
If they see you pouring a standard cylinder sample for testing they know not to screw with you
Or else they will deliver the lowest end cheap stuff for sidewalks
There are many quality grades for concrete and they behave very differently
The highest grades you cannot use any ram sets type anchors they just bounce off, it’s funny watching the gas and power company try to use their tools on it and scratch their heads why nothing seems to work

Often the price difference is trivial for a small volume like a house or garage foundation, it might only be a couple hundred more for much better quality cement

I usually never accept anything less than 33 MPa for my jobs even if I’m only making art work because, why not right?
-s

Use a crushed stone mix with nothing larger than a #8 in it. Compact everything! You want at least a 1' X 1' footer with 2 #4 bars and 6" welded wire mesh in the slab. #3 bar 3' on center is better. Use 4000 PSI concrete with crushed stone. Do not use round stone. The cost difference on the project is minimal. Keep all the steel a minimum of 2" from the edge of the concrete. Piers need to be a minimum of 2' X2' to do much. Keep in mind anything like a lift you may be installing and thicken the slab there. I would stay away from casting plates and use a 1/2" diameter tapcon. I'm a commercial general contractor.