cement slab

[alchemysa]

I recently concreted my shed. Size was 23 x 20 feet. (just a bit bigger than yours). Average depth was about about 4.5 inches. Including the path across the front it took 5 cubic metres at $230 a cubic metre. (5 metres is 6.5 cubic yards.) I used 5mm mesh as reinforcement. (6m x 2 metre sheets. 3 sheets at $60 a sheet). I think this will be ample strength for what I plan to park on it. Preparation is the key of course. You need to really pack the base down hard. Allow yourself a day at least to just spread the fill and level it and pack it down.

Don't underestimate how much concrete you need. It can be a disaster if you run short. (Its harder than you might think to get a consistent 5'' depth so allow for some variation.) Better to buy a truckload of concrete and have some extra formwork boarded up in case you have some leftover. As you can see from the pic I had formwork ready to concrete along the side of the shed. (Drat, now I'll have to mix that bit myself!).

You can do all the preparation but don't try and level the concrete yourself. Hire a guy who knows what he's doing. Its not a job for beginners. One 'professional' with a leveling screed and a motorised 'power trowel' is all you need to pay for. Apart from that, you and a buddy can man the wheelbarrows and of course there's the concrete driver who'll man the chute. 4 guys in total. Its not a big shed you are concreting so any more than that will just get in each other's way. If the job is straight forward then the truck will be on site for about an hour. The professional guy will screed (level) the concrete as you barrow or chute it in. It can be a relatively slow process. Its not simply a matter of dumping all the concrete in the middle of the shed and spreading it out.

You might also consider concreting a path at the front of the shed like I did. I'm really glad i did it at the same time rather than later. Its too small an amount to get delivered in a truck later on and it looks a lot more professional having a nice transition from inside to outside.

What surface finish do you want? I wanted a smooth finish inside so it would be easy to sweep. (Thats what the power trowel is for.) But the front path is a sponge finished so its non slip.

If you want a smooth finish count on the professional guy being there all day for a job like this. He has to wait quite a while for the concrete to go off before he can trowel it.

 

[AHNC]

I would stick with mesh. I've done plenty of interstate bridge decks and hwys and we used 6" wire. 45 years later, they are still there...although they and I are showing signs of wear. However, don't use the rolled wire. It is just a giant pita, which with limited experinece you do not need. Get the 4x8sheets and lay them out as you go. Overlap one grid. Get a 3-4'x2"x2" and pound a nail in 3" from the bottom. You can then push the wire to the proper depth as well as being able to hook it and pull it up to proper depth. You will like the results.

Prepare your site for drainage, if necessary, prior to doing the slab. I'd also recommend that you park you tractor and measure it's width plus the dimension you need to get on and off and work on it. 14' goes away in a heck of a hurry. Might I suggest 16? I just love this site. It is so easy to spend other folks money:laughing: Good luck!

 

[buckeyefarmer]

Question,
If you pour an apron outside your building while pouring the inside, would you pour it as part of the same slab, or would you put a joint at the door and then pour the external separate?

I just priced 4000 concrete $2.50 yd more than 3500 psi, so not much difference. Rebar has doubled since I last bought any.

 

[lovemytoys]

Question,
If you pour an apron outside your building while pouring the inside, would you pour it as part of the same slab, or would you put a joint at the door and then pour the external separate?

I just priced 4000 concrete $2.50 yd more than 3500 psi, so not much difference. Rebar has doubled since I last bought any.

if this was for me i was going to pour only enough for the shed

 

[buckeyefarmer]

sorry, was asking a question for me inside of your thread..

 

[Duffster]

Question,
If you pour an apron outside your building while pouring the inside, would you pour it as part of the same slab, or would you put a joint at the door and then pour the external separate?

I just priced 4000 concrete $2.50 yd more than 3500 psi, so not much difference. Rebar has doubled since I last bought any.

It should be separated IMO but that doesn't mean it can't be poured at the same time.

 

[alchemysa]

Question,
If you pour an apron outside your building while pouring the inside, would you pour it as part of the same slab, or would you put a joint at the door and then pour the external separate?

In my pic above you can see the small path or apron at the front of the shed. This was poured at the same time and is simply a continuation of the shed floor. It suited me perfectly to do a small apron like this at the same time. (A large apron would need expansion/crack joints so that might be a whole different matter.)

Although the garage floor itself is perfectly flat the apron on mine slopes down significantly. (About 3" in just 18"). The slope was created simply by manipulating the wet concrete. (The formwork of course needs to duplicate the slope that you want). There was no formwork dividing the shed floor and the apron. The concrete finishing guy simply established the level by banging a rebar peg into the ground in the middle of the door. The top of the peg was the height he worked to.

However if you are using a vertical opening door (like a roller door) then you should probably run form work across the door opening and do the apron as a separate, lower, slab. You can then put a 1" lip just inside the door to stop water and dust blowing in.

 

[herd]

Question,
If you pour an apron outside your building while pouring the inside, would you pour it as part of the same slab, or would you put a joint at the door and then pour the external separate?

I just priced 4000 concrete $2.50 yd more than 3500 psi, so not much difference. Rebar has doubled since I last bought any.

Best to pour at the same time if you can afford it on the project. Either use a metal keyway at the point the ramp begins or either trowel cut an expansion joint before it hardens too much or saw cut the next day/.

 

[AlbertaDan]

this will be my first slab .any input would help alot.slab is going to be 14'x20'x4".i dont think i can do it with a small mixer so i think im going to order a truck.do i need gravel and a vaper barrier?? also i heard the the outside edges 8"back should be 6" dep. i hope i said it right .they say it will help with shifting and frost lift .what do you think

My garage slab is 22X26 in size. I agree with another poster, the 4" thickness is thin. Mine varies from a minimum of 5" to close to 8" at the back. I put vapor barrier under mine and have never had a problem with moisture coming through the slab(concrete is porous).

For strength i used 1/2" re-bar spaced about every 12" in both directions. I needed to make sure that the slab never moved, as i live in northern alberta so the ground heaves every winter. Mine is 11yrs old and no signs of cracking. Because i used re-bar and the slab is thicker than most build i never put any control joints in it. I have had my full size truck, motorcycles and a car in it with no problems.