Concrete Job

Jobs like this will depend largely on location. Where the shed will be on your lot (can a truck get there or will everything have to be carted in from the street?).

How close are you to a concrete batch plant? Those trucks don't run for nothing and drivers are paid pretty good wages.

Will the concrete have to be mixed on-site? Mixer available? Gravel, sand, concrete, etc? Water on-site, or can you run a hose to supply the mixer near the job site?

8' X 8' is 64 sq. ft. A 4" slab will take a bit over 21 cu. ft. of mix. A 6" slab will take 32 cu. ft. of mix. Running a footer around the edges makes for a much stronger slab (monolithic pour), so a trench about a foot wide and a foot deep is probably a good idea, with 2 or 3 pieces of #4 or #5 rebar. This raises your concrete mix requirement to about 40 cu. ft. for a 4 slab, or about 46 cu. ft. for a 6" slab. Some welded steel wire mesh is advisable for the floor slab reinforcement.

Concrete is usually ordered and sold by the cubic yard. One cubic yard is 27 cu. ft. Your job requirements are very small for a batch-mix truck delivery, so you can expect to pay a premium price, as compared to others ordering truck-loads for larger jobs. If you take this route expect to pay for 2 cubic yards, and the driver/operator will want to have a place very nearby to dump any excess left over after your forms are filled (they usually won't take anything away with them).

Getting the forms leveled is not really difficult. This can be done with a good carpenter's level (4' or 6') working across the 4 corners or a string line-level corner to corner.

Squaring the forms is equally easy. Just measure on a diagonal from corner to opposing corner and make sure that these two dimensions are exactly the same. Your forms will require 2- 2X6 boards 8' in length, cut to exactly 8' (most are a hair longer than nominal dimension) and 2- 2X6 at 10' length cut to 8' 3" (8' slab width plus two side forms of 1.5" width each), nailed securely at the corners. Once squared up the forms should be heavily braced (heavy stakes every 12" to 16" all around driven deeply into the ground, using offset braces if the ground is soft). Then the forms can be leveled and nailed off to the support stakes (use two-headed nails so disassembly of the forms and bracing is easier later on).

Site prep: Remove all vegetation completely, including grass roots. Trench out for footer around perimeter. Lay about 2" of sand over slab base and bottom of footers. Dampen sand prior to pouring concrete (prevents excessive water loss from the concrete mix, which affects curing and final strength). Lay wire mesh for floor, held about 1.5" above the sand with small pieces of brick or similar. Lay rebar for footers, bent at 90 degrees around corners, ends lapped about 1' and secured with heavy wire ties, held about 2" to 3" above the sand on small pieces of brick or similar.

Assemble and install forms as described above. Pour concrete mix, pushing into footers with shovels and roughly leveled just above the form boards. Use a striker board (2X4-10' will work) to work concrete surface to level at form tops.

As the concrete settles the gravel will tend to drop down and the "cream" will rise to the surface. Then we use a concrete float to smooth the surface perfectly. After a few hours (and several floatings) the concrete will start to cure and the edges can be done using the edging tool. If desired a push broom can be used to apply a slight texture to the surface (safer to walk on than a slick-finished floor).

Keep the concrete dampened throughout that day and overnight. Concrete doesn't actually dry out; the water is an essential ingredient in the mix for proper curing and final strength. A garden hose with mist-spray nozzle works nicely for this.

Day two the forms can be struck and removed. The use of two-headed nails will be appreciated at this stage. Boards used for concrete forms are seldom useful for anything else, so they will need to be hauled away.

I would allow the new slab to sit for a week or so before building on it.

So, for a contractor to do this job will require two men for about 8 to 10 hours total, about 2 yards of concrete, 500 lbs. or so of sand, some lumber and nails, use of some basic tools (shovels, levels, measuring tape, saw, hammers, floats, edger, etc) and a truck for transport and debris removal.

16 to 20 hours semi-skilled labor will probably cost about $250 to $300 in wages, plus workers comp, unemployment insurance, FICA taxes, and any employee benefit plans, so probably $350 or so contractor's cost. Lumber and nails about $40. Concrete probably about $250 or so. Sand about $20. Rebar and wire mesh about $60. Gasoline for truck, other incidentals, add $40 as a rough figure. So about $700 total.

Assuming the contractors you are getting estimates from are going to be a part of the labor crew, the estimates you are receiving indicate the contractors are basically working for wages rather than much in profit. The contractor can then use a relatively unskilled helper at smaller wages and pay himself a bit more.

If I were doing small jobs like this I would try to schedule two or more such jobs at the same time, running a crew from site to site, and having the concrete deliveries done one after the other. Then there might be a bit of profit in addition to working for wages.

Of course, you can always pay for all materials (about $300) and hire a handyman to do the work, maybe act as the helper/laborer yourself. Might save a couple hundred bucks. This assumes that the guy you select actually shows up on time to do all the prep before the concrete arrives and stays around to finish up after; otherwise you are out some money without getting what you need done.

Small jobs are considerably more expensive (per foot, per yard, etc) than larger jobs. They have to be, otherwise there would be no reason for anyone to take them on. Using a licensed, experienced, reputable contractor is probably your safest bet for a good outcome.

Best regards.

If I wanted the job done by the "pros" and done quicker than I could do it then a price of $600-$700 would be worth it to me.In my younger years I would have no qualms about doing it myself and also doing it in a weekend or two.

No offense to some of the posters here but a 1'-2' footer is pure overkill for an aluminum shed.As long as you have a good base to start with you would be fine with 6"-8" of concrete with rebar laid in.You could easily park a lawn tractor in the shed with no fear.

Before the concrete sets up you would also want to stick threaded bolts in the cement at measured spots so you can anchor the shed down later.Getting the foundation as level as possible should be a priority but not a game killer.Even the pros aren't perfect.They often use shims or weather stripping which serve to level the project and weatherproof the bottom from water leaking in.

It's really an easy job to do.You just need a plan laid out ahead of time for what you need and how to do it.

coltle6920 said:

If I wanted the job done by the "pros" and done quicker than I could do it then a price of $600-$700 would be worth it to me.In my younger years I would have no qualms about doing it myself and also doing it in a weekend or two.

No offense to some of the posters here but a 1'-2' footer is pure overkill for an aluminum shed.As long as you have a good base to start with you would be fine with 6"-8" of concrete with rebar laid in.You could easily park a lawn tractor in the shed with no fear.

Before the concrete sets up you would also want to stick threaded bolts in the cement at measured spots so you can anchor the shed down later.Getting the foundation as level as possible should be a priority but not a game killer.Even the pros aren't perfect.They often use shims or weather stripping which serve to level the project and weatherproof the bottom from water leaking in.

It's really an easy job to do.You just need a plan laid out ahead of time for what you need and how to do it.

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A footer may be overkill for a lightweight shed. But I live in an area with some serious frost-heave issues and expansive soils, either of which can effectively destroy concrete flatwork in a season or two. It is so much easier and less expensive to over-build a bit and never have to worry about trying to fix it later on.

With your frost heave problem, I would go with a 1' deep footer with the base of it about 8" in width. Over dig that so you can go with the 2" of sand in the bottom. Over that put two ea. 1/2" rebars with a 12"/14" lap well wired together at the joints. Level and square the forms as described above. Again, make sure that is no organic beneath the slab. Have a 10/12' twoxfour available for a screed. Pour the concrete and level it with a shovel. Keep the screed working toward where you are placing the concrete. I would specify at least 3500 psi grade concrete. I would also make the slab depth 3.5" (width of a 2x4) or 4" depth. Any more is overkill. I would also NOT use mesh in the slab. The use of mesh is oversold and people expect it to add to the strength of the resulting slab. IT DOESN'T. Mesh is just to conduct & control the 'heat of hydration' out of the slab uniformly. It is most needed in big fast drying slabs. You won't have either. Some batch plants in frost country won't even provide anything less than 4500 psi anymore. Rent a long float, knee boards, hand float and a trowell. This 64 sq. ft. slab is nothing to finish. Again watch a few of those youtube videos. In an eight foot x eight foot slab, I would place expansion crack grooves at the dead center each way. If the ground heaves the slab will crack slightly in those grooves and no other place. If you wonder if I know what I'm talking about, I was a concrete placement construction engineer on the installation of the last generator in Hoover Dam. My Dad was one of the superintendents of construction thruout the construction of the Dam. He taught me everything he knew.... BTW, Hoover Dam was built using 2500 psi concrete, but its foundation wasn't subject to any frost heave either.

I don't know about up north but down here you don't need footers for that small of a shed.

Less talk and could have already done the job and drinking beer.

The last concrete job that I did was to pour a new sidewalk in front of our house. Everything was ready, son and sons- in - laws ready to help. Come the concrete and no help. My wife is a trooper and she helped me but 80% through, we started to lose our pour. Just then a guy on a bike stops and starts to watch us. My wife asks what the h••• is he looking at, while wiping sweat off of her forehead. Guys says, that concrete was his profession and it was fun watching amateurs screw up a job. My wife swore, a rare thing and told him to get off of his blankety bike and help.
He said that he would as long as we were not Republicans.
At that point I swore, and equally unusual thing and told him that actually I was a Maoist. Biker dude shrugged and said that I must be lying like all capitalist pigs. He helped and saved the job. My wife slipped him $40 bucks and I did too. Biker dude rode off laughing at how he got paid twice.
I drank the beer that was chilled for the no show boys and decided then that I needed to get the h••• out of Portland.

You could always make a wooden floor at 1/3 the price and trouble?

I would prefer 18" deep and 12" wide on the perimeter (we call this a rat trench),

Don't know if it's feasible for the OP but have you considered a wood shed? I had an 8'x8' shed in my backyard back East.It was built on 2-6"x6"x8' runners treated for outdoors and laid on a gravel bed.No worries from frost and it's even in a flood zone.Still standing and fully functional after 30yrs now.

If you are concerned with frost upheaval in your area check with your local building inspector.Chances are the frost line is 30" or more anyway.I would bet that an inspector would only be concerned with frost upheaval when something is built connected to your house like a deck and then the posts would be required to be sunk around 36".

If you've lived in your house for any extended period you would know if frost upheaval has been a factor in your area.Just look at the sidewalks if you have them.They are usually the first to go and not very thick to begin with.

My father who was a self taught mason and general contractor is probably turning over in his grave right now.

Don't overthink it...Just get the job done! This isn't the Hoover Dam.It's just an aluminum shed.

I built bridges for a living for 30 years. There's a lot of concrete in a bridge. Most people don't know how to form up a slab and pour concrete. I'm a licensed surveyor and I know how to form up a slab. I've seen thousands of yards of concrete poured and finished. Don't screw around with this. The folks that want to do it on the cheap usually don't know what they are getting into. I hire the pros and I know how to do it.

I hope that tells you something.

The Shed

I already have the shed. It's on a pallet in the shipping box sitting at a corner of my parking area under a tarp. Been there a month.

A month ago, the contractor said he was doing a small job in my area (rural) and would pour my pad at the same time. I've called him every week since and get more promises. l called two other contractors and they won't even bother with me.

Yes, I thought of a pressure treated wood foundation. Sounds better with each passing day (or week).

I thought of stopping at Home Depot and getting a load of 4" concrete blocks for a foundation.

For no more than an 8'x8' shed used for storage, your idea of using concrete blocks for the foundation of the shed makes perfect sense to me. If it is a 'hobby' building and you need a sturdy floor for some reason, go with the concrete poured in place. It might not be "Hoover Dam", but there is no reason to do the job halfway only to have to do it over again in the future. .............YMMV

Concrete is hard to fix.Do it right.

It's a freaking shed , for goodness sakes. A 4 inch slab will "float", if it isn't connected to something. To stop "frost" heave, you have to put footers down below the frost depth. You don't need concrete footers for a garden shed.

Wire mesh in a slab is not placed to transfer the heat of hydration. It is put there to keep the slab together (in same plane), when it cracks.

A 4 inch slab the size you are talking is only bout .8 cubic yard, and a lot of plants will laugh at you for attempting to order that amount.

Easy amount to pour with 2 people who know what they are doing. Unless it ends up being a hot day and you get a "hot" load let over from another project. Course the driver will willingly remix it "soupy" for ya, kinda ruining the purpose of concrete slab.

zeke, he who's back is bad from a decade of concrete finishing. And that is hand finished (including joints) city walks. Makes it tough to pick up all that free brass at range after the holidays.

As a side thought, sand attracts ants but crushed fine limestone doesn't.

I poured and finished my patio. 14 X 22. I had some 2 X 6 lumber on hand, so that is what I used for forms.
Covered for 30 days and kept it from drying too fast. Zero problems with it, and have enjoyed it for more than 5 years.

It really isn't difficult.

Something to consider, if you have a 8'x8' pre fab shed, extend the slab 3" or so on all sides..This allows you to slope the 3" away from the shed, caulk the bottom sill of the shed to prevent water runoff..
Placing the crete with a wheelbarrow would not be out of the question, but that would be a 2 man job, one wheeling and one straight edge man..

I did my little shed years ago and just put a wood floor down. Considering the price, I would consider a treated floor, elevated sufficiently to permit air flow beneath, you could do a cost analysts of material and looks like a fun weekend project for the floor. If you wanted a concrete floor for an 8 x8, like one of the previous posters said, this is only 64 square feet. What about 64 of those 1'x1' concrete pavers at the local HD? You would be looking at around $ 100-125 for material, I would think. Level the spot, throw down some sand or small gravel to level the pad and place the pavers for the floor. Saving would buy a lot of beer you could sit in the shade and admire your new building when it was completed.

Drm50 said:

Pouring small slab like that is fairly easy. If you pour yourself
you need one helper at least. I use to do all my own crete,
now I only do steps. My back won't take it any more. I was used
to much when I was new. Best advice is hire the pros/ insurance.

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I used to do a lot of things that my back won't let me do any more. It sucks to get old. Now I have to pay for work to be done.

Option 5.

Build a foundation out of 6"x6" treated timbers, fill in the floor with crushed gravel.