# Would 3 or 4 yards of concrete cover a 12x20 garage?



## Bondo

Ayuh,... Do the math,... a yard of concrete is 27 cu. ft....

12'x 20'x how many inches,..??


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## Daniel Holzman

For the footing, each linear foot requires 1 cubic foot of concrete. You have 60 linear feet of footer, hence 60 cubic feet required there. The slab is 240 square feet, so for a 4 inch thick slab you would need an additional 80 cubic feet of concrete, for a total of 140 cubic feet, which is a little over 5 cubic yards. Due to spillage and waste, best to order 6 yards of concrete. Unless of course your slab is not 4 inches thick, in which case you need to modify the computations.


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## CJ21

Yes the slab is 4'' thick.


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## joecaption

I personaly would never suggest anyone DIY there own slab. Seems ike a simple job, but it's not.
It's a one shot deal, once that truck pulls in there is not do over or just make it work.
Even the lay out, footings, height of the slab, the slope toward the front can be tricky.
Have you taken into consideration that the bottom row of siding needs to be at least 6" off of grade?
Have you concidered using stem wall constrution?


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## woodworkbykirk

4" slab on a 12 x20 works out to .3333x12x20 / 27 +10%= 3.256 yrds round up to 3.5 yrds if you can get 1/2 yrd ordered otherwise get 4


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## concretemasonry

Better to order too much since concrete is not that costly once you reach the minimum delivery amount. Nothing is worse than coming up short if you did not have base under the slab graded as accurately as you want you pencil will be in figuring costs in advance.

Plan ahead and make sure you have something formed in advance that you ultimately need - sidewalk, apron, etc. to use up any excess. Much better than just dumping it in the wrong place.

the biggest mistake with concrete pours is to not have enough (poor concrete job with cold joints) or enough help to place it quckly if the weather turns. - Also have protection for rain or snow.

Dick


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## CJ21

I understand that pour concrete is not a DIY job, thats why I thought about doing a wooden floor.


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## CJ21

I figure it was 4 yards.


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## BigJim

CJIII said:


> I figure it was 4 yards.


CJ, It would be a little over 3.5 yds for just the slab, but you said you were pouring 12X12 footings so you will need at least 6 yds like Daniel said.


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## ddawg16

Are you pouring that with a totally flat floor? No stem wall? 

For reference, my floor is 20x25....it took 20 yards of concrete.....oh, the footing is 18"w x 24" deep and has an 8"h x 6"w stem wall all the way around. I love that part...it gets my walls at least 8" above the ground and on the inside....all my cabinets sit on the lip of the stem wall anchord to studs....nothing touches the floor....makes it easy to wash out the floor.

If you want to see pic....click on the garage build link in my signature.


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## CJ21

Ok thanks!


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## CJ21

The reason I wont concrete is that I will be using the garage as a woodworking shop!


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## joecaption

Going to be tight in that small an area trying to use it for a wood working shop.
Have you done a simple lay out on some graft paper to see how it's going to look.
Just been there far to many times. Built the garage, moved eveything in, find out it's to small and have to go back to working outside.


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## CJ21

I know its small but my current shop is 10x12 shed.


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## oh'mike

CJ---I'm not a concrete guy--But I've helped a few times---you will want to cut your stakes down so the top of the form is clear----then use a 14 or 16 foot 2x6 as a screed board --

this will get you somewhat flat and smooth--

Rent a 'bull float' to get it smooth----you may be happy with that---for a good surface you will want a 'pool trowel'---that is a hand held trowel with round ends---waiting for the concrete to reach a trowel able firmness will make you nervous----do the pour on a cool day ,in the morning if possible,

Kneeling boards will be needed---


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## joecaption

The first shed I built for myself was a 12 X 16. Once it was built I added a work bench on one side and a radial arm saw on the other plus all my other tools.
It was less then useless, and ended up using it for nothing but storage.
Something as simple as trying to lay a door flat for sanding and painting was a nightmare. Just not enough room to work around it without bumping into it.
Everytime I wanted to plane, rip a sheet of plywood, cut some 2 X 's to length I ended up outside rough cutting it.


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## CJ21

Thanks Mike, I understand that Joe, my old shed is the sameway? Mike do I use 2x6's for form work?


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## oh'mike

You will want 2X material for the forms-------wet concrete really pushed hard--so stake it well and have a few extra stakes waiting in case something moves while you are pouring--

I hope one of the finishers chimes in ---concrete needs to set up just a bit before the troweling begins if you want a smooth finish---it's hard to describe---the one finisher I knew sat next to the freshly floated stab and ate his lunch and tested the surface with his trowel--

when the cement was 'just right' lunch was over and he laid his board onto the wet concrete and started troweling.


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## CJ21

I hear you have to let a slab sit before troweling.


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## oh'mike

CJ---Remember---it's just a small out building----what could be a better place to learn a new skill---

Remember this,too.----you have termites and plenty of rain down there--so make sure the slab is high enough off the surface of the ground to keep your sill plate and siding safe from mother nature--


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## CJ21

Ok thanks Mike, I may give it a try.


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## oh'mike

You will do well CJ --I look forward to seeing the new work shop----Big Jim (Jiju1943) has downsized to a small shop----you will figure out how to work--might be, doors front and back will let you rip long stock without having to move your big saw so often.


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## BigJim

oh'mike said:


> You will do well CJ --I look forward to seeing the new work shop----Big Jim (Jiju1943) has downsized to a small shop----you will figure out how to work--might be, doors front and back will let you rip long stock without having to move your big saw so often.


Hey CJ, you will know me better as "fish" from the BOC, just look in Jim's Wood Working and you will remember me. It is good to see you again buddy. Mike is right, I have downsized from a 5,000 square foot building to a carport 12X18. I had to get rid of a lot of my big tools and am still in the process of trying to get organized. You have the opportunity to plan your shop and get organized from the start instead trying to fit a ton of tools in a very small space. 

I have built complete kitchens and complete custom stairs and other things right out there in my little shop, it can be done. CJ, while you are still a young man, you might want to learn how to use hand planes and understand them, once learned, they can really be a big help in your line of work. There are many times I could have used hand planes and older tools do make my job much easier. I was too busy trying to earn a living to learn the old tools.

You will find you can do a lot of work in a much smaller place using hand tools. I wish I had discovered how useful the old tools were when I was in business. Using the old tools and power tools is a win win situation in a smaller shop. Sorry to be so long winded here.


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## CJ21

Thanks I like hand tools, I had a big collection but I sold some of them. I been looking at putting my 10'' Unisaw on wheels. So I can move it around if needed.


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## oh'mike

I'm glad you started a thread---I wish you were closer--your love of wood and making do with what you can afford is so refreshing in this day of," I can not do that because I don;t have a----"

Keep up the good work---Mike----


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## CJ21

Mike do you do any woodworking?


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## oh'mike

Yes I do---book cases--cabinets-- clocks --tables--miles of trim--doors--mantel pieces---trellis work--

My table saw is huge---three router tables---close to 200 router bits---And I buy my hardwood at the mill 200 to 300 BD foot a load---so ,Yes I do---I'm Mikeswoods over at CT.


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## CJ21

I am looking at doing bookcases, fireplace mantels, bathroom vanites, built-ins and carpentry projects for pay. Do I need to bring in fill for the slab?


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## oh'mike

You want the top of the slab about 6 or 7 inches above the surrounding soil so your siding is safe from water and bugs----so some fill will be needed----3 or 4 inches worth---

Some of the fill can be from the excavation of the thickened part around the edge of the slab--but some will need to be brought in----

Book cases and other interior work is fun---I strongly suggest you start with some out door projects---Planter boxes ---deck benches---trellis work and (don't laugh) Mail box posts.

I firmly believe a person could make a nice modest living being "The Mail Box Guy"--
If you had a trailer or pickup truck set up with a variety of nice mail box posts (and mail boxes?)

Send out fliers a few days ahead--"The Mail Box Guy is coming on Saturday --Look for his truck and pick out a post----Special pricing if he can install it the same day!!!"

All you would need is a healthy set of muscles--a warm smile and a post hole digger---(and a receipt book.)

That would also lead to the sale of trellis work--log racks---planter boxes and other work---

How's that for an idea? 

Next time you are out for a drive---take a look at the ugly mail box posts-----You would want to charge a good buck for the service----

work with a smile and make posts that are something to brag about----Mike---


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## CJ21

Thanks for the advice, Mike it was really helpful.


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## BigJim

Mike that is a good idea, I see why you make the big bucks now.

CJ, when you pour your slab are you going to do a monolithic slab (thick edge slab) That would be the easiest for you. Be sure to put reinforcement concrete wire and 6 mil poly, termite treatment and post hole every 4 feet on center down to solid ground. You might want to think about stubbing out for water and future electric in your slab. For sure if you are coming in underground with the electrical, be sure to install a pipe for the wire to come up in the wall. Here is a sketch of a monolithic slab.


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## CJ21

Yes Jim, thats what we do in Alabama is a monolithic slab.


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## CJ21

Mike, I am CJ21 over at CT!


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