How big of a slab could I do by myself?

[newbury]

OK, I finally got around to doing this.

I decided to divide it into six strips, each strip was 33" wide and 10'6" long.

I ripped 4" pieces of treated plywood and Tapconned them to the walls, I figured that would give me a level and also a bit of an expansion joint. The building had a concrete apron that was even with the bottom of the doors and then a gravel floor for the rest of the interior, so the first step was to remove enough gravel to make room for the concrete.
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This ended up being a pretty big job, I hand shoveled about 4,000 pounds of gravel out. To get the level right I built a box out of 2x4's, got it level with the plywood at each end and then scooped out the gravel in the middle. Then slide the box over and repeat. I sloped the floor somewhat toward the door, partly so that it would drain but mostly so I didn't have to remove so much gravel.

Next I put down sheeting and forms. The form was just two pieces of 2x4 screwed together at a right angle. I cut slots for the rebar in the vertical piece, and then cobbled together a few scraps of 2x4 at each end to hold the form to the plywood. I did a form at each end so I could do two pours at a time. This worked really well, the forms were really solid, they never moved and they gave me a good place to stand.





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The first pour:

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The final pour:
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It ended up being 105 60-pound bags, about 18 bags per section. I mixed them with a Kobalt electric mixer I bought at Lowes. I did two sections per day for the first two days, and then one a day on the next two. The quickest section was under 90 minutes, the slowest was over two and a half hours. I raked the concrete out with a garden rake, screeded with a 2x4 and then touched up with an 18" float. For the sections by the door I could pour straight out of the mixer, but for the back sections I had to dump the mixer into 5-gallon buckets and carry it to the back. Overall I felt that was a manageable quantity for me to handle by myself.

Overall verdict: I'm pleased but not proud. I got exactly what I wanted, a solid floor that I can work on. The appearance is pretty mediocre but I can live with it. Total cost was about $550 for the concrete and about $100 for the rebar.

Great job!
One question pops to mind - Why did you put your first "pour" down at the front and back?

 

[quicksandfarmer]

Great job!
One question pops to mind - Why did you put your first "pour" down at the front and back?

I wanted to be able to do a second section while the first one was still setting, so the job wouldn't take six days. I had the bags outdoors and didn't want them to get rained on. For the front pours, once I had a section done I could roll the concrete mixer on that section while I poured the next one, but I had to wait a day for the section to cure. For the back sections there wasn't really anywhere to put the mixer, I couldn't put it in an unpoured section because the rebar was in the way. So I mixed in the front, poured into five gallon buckets and carried it to the back.

I only did two back sections that way (which was enough!). Once four sections were done and there were only two left, I couldn't do them both at the same time because the forms would be in the way. So I did one pour a day and did them both from the front. The final pour had no forms, just the section on either side. So it was two two-pour days and two one-pour days. Or really two afternoons and two mornings.

 

[bigtiller]

That's a heck of a lot of work to spread it as it comes out of the truck and then screed it after your done spreading it. And hopefully it's not already setting up when you start to finish it.

That's for sure!

I pored a lot of concrete years ago, and when I was about 30 I pored ~ an 8x40 by myself.
It was enough of a workout that I decided I would never do that again by myself.

 

[deezler]

That's a heck of a lot of work to spread it as it comes out of the truck and then screed it after your done spreading it. And hopefully it's not already setting up when you start to finish it.

Screeding my parking pad was definitely the most difficult and stressful part. 13' and 15' widths (starting at 18' wide at front!) in each of my two main sections meant using a 16' or 20' 2x4 and burning up our arms and shoulders trying to work it back and forth. I imagine there is a better way (power magnesium screeder for example) but I was determined to do it the cheap way, haha.

Even on nice cool, shady days, it was setting up by the time we finished screeding (took multiple passes to get it good enough), which meant no time for a break, had to broom finish right away.

 

[deezler]

On squarish slabs; I think the reach out has a bigger effect on the ability for 1 person to finish than the total CY or SY. It's easier to pour and finish a 9x60 than a 27x20

Yep. Super hard to screed a 20' or more pad. How do you even do it without professional tools and a whole team working at once?

We had a lot of trouble on my pour getting the broom finish across a 15' wide pad - had to tie a line to it for a 2nd person on the far side to help carry the super heavy broom back across. I had it on a long extension pole but once the broom was soaked in concrete, weighing 40 lbs, you couldn't lift it back across without help. Bull float-ing beyond about 10' out was very hard also.

 

[EddieWalker]

For me, it's the stress and panic of HAVING to get it done as fast as possible that wears me out the most. 12 x12 is about the biggest I'll go when mixing 60 pound sacks of concrete and doing it all by myself. If it gets much bigger than that, I'm doing it in sections or hiring a crew.

If I bring in a cement truck, then I'm dealing with more concrete at once then I can handle by myself. It's just so time consuming and physically exhausting to spread it as it comes out of the chute to do by yourself.

 

[JJT]

In my younger days I thought nothing of doing a 10 yard pour by myself, (redimix). I'm getting ready to do an 8 yard slab in two weeks and have already lined up 3 helpers.....

 

[MossRoad]

That's a heck of a lot of work to spread it as it comes out of the truck and then screed it after your done spreading it. And hopefully it's not already setting up when you start to finish it.

I had to pour a footing for a 24x32 garage about 1990. I had three friends lined up to help. They didn't show. I did it by myself.... and it was HARD@! The wheelbarrow broke shortly after starting. Fortunately, the cement truck driver took mercy on me and took his truck off-road and was able to get the chute over most of it. He had to drive over several piles of sand to get there. I gave him all the cash I had in my wallet after that.

I learned two things that day.
1. don't pile the excavated soil near the excavated hole, as it will block access for everything else until the project is back-filled.

2. get better friends.

 

[MossRoad]

...I'm doing it in sections or hiring a crew.

...

I did ours in 8X24 sections. And I had a crew... my wife, daughter and her fiancé. Surprisingly, they learned very quickly. All I had to do was haul the concrete in the tractor bucket and do the final finishing. They did all the rest.

Wife says she will never be talked into that again.

 

[bigtiller]

This "roller/tamper" is a back saver. Every DIYer needs one to get himself out of trouble. It pushes the rock down and brings up some fresh gravy, giving you a free do-over for finishing when the concrete starts stiffing up.

It buys you an extra 20 minutes or so before the bull-float is used. I have a 36" one and use it nearly every time.