DIY Slab concrete

[NDJ]

This will be a slab for a future shed. At this point its 18'x11' and will eventually be larger with more sections added. I am breaking it into smaller pieces to manage it and also minimize the impact in case something goes really bad. Going to do as much of the slab as I can on my own; Very hard to get call backs around here for "smaller" work since the construction biz is still booming. Really dont know what I am doing but Youtube has given me confidence (perhaps false)

My lot has a fair bit of slope (about 1:10) so have to deal with that. I was able to find a guy on marketplace who works a bobcat and he did a decent job levelling the area and stripping the topsoil. And so with about 15 yards of gravel delivered and spread by hand along with renting plate compactor, I had a half decent subgrade.

 

[NDJ]

Forms in place. 2x6 3 sides and 2x8 on near end. 10mm rebar around perimeter with mesh spanning the rest. I estimate 100 cuft of concrete needed.
There was only one concrete co that was willing to deliver this and they have only one day when they can do it - On a 60% chance of rain day. Myself and a friend will be doing the placing.

 

[billconner]

Looks like a good start. Are you mixing on site or getting ready mix delivered?

I've been doing all my own prep work - forms, gravel, mesh, etc. and hiring someone doing Saturday side jobs to pour and finish. Saves a lot. I don't think I can handle pour and finish myself, and I won't have a bull float hanging around to my death.

 

[OCD]

Nice prep!!

 

[Zeke]

18 x 11 doesn't look so big until you're on you knees in the middle. That's gonna be a hustle for just 2 guys. I will take 2 guys just to run the screed w/o breaking your back. That doesn't provide for a shovel man. Are you going to run that out of the chute, or pump? Either way, some operators are better than others. So plan on spending a few extra bucks for some stand by time. Don't let the driver or pumper rush you. The concrete will set up in the pattern you placed it, shadows, etc. notwithstanding. So if it takes you a half hour more to get it screeded, the last area should wait a bit for you while you work the front.

However, concrete is exothermic, so once it starts setting, it's not waiting for anyone. Just work it end to end in the order placed. Don't overdo the shaded areas, give them some extra time. If it rains, you're screwed unless you can work under a tarp. You cannot finish concrete with water coming down on it.

 

[brownbagg]

you need a footer on the edge

 

[Toolfool]

Planning a lot more stakes around the outside of your forms ? Wet concrete is very heavy.

 

[Dagny]

Yeah more stakes or pack some of that dirt around the outside.

 

[PCustoms]

you need a footer on the edge

For a shed?

 

[speed bump]

Your going to want to step everything around your pad (or put in a retaining wall) otherwise it's going to be pushing on your shed wall eventually.

Lots of stakes, get at least 3 people two to screed and one two shovel.

 

[billconner]

Definitely need another person. I staked my forms 3' on center max based on what I read. Based on the grade, can you lay block around those edges, enough to keep framing at least 8" above grade?

On the footer, if this is a light wood framed structure (even with a few block courses) and that's basically a 5 1/2" slab at edge, and ground under is solid, I agree no additional footer is necessary.


Dont forget anchors! J bolts or rebar for blocks or whatever.

 

[JoeMcGov]

Holy ****. That is one of THEE nicest "I don't really know what I'm doing" slab preps I've ever seen here on GJ. Very well done.

Proper prep is everything for concrete. You've done very well.

 

[Leaflessshadetree]

How big will your shed be? Are you planning on this and the other pieces to form a single flat slab? If so you will want the reinforcement (rebar or mesh) to connect the individual pours so they stay even.

 

[NUTTSGT]

Got floats, trowels or broom for the finish work ?

 

[PWC Repair]

First.....I'm NO expert! The first one I ever poured was 12'6" x 18'6". I built a 12x18 shed on it. Mine has no footer and has been fine for the last 20 years. I have to assume you're laying some block? Otherwise, you'll have water and mud in your shed the first time it rains. Even if you ARE placing a block stem wall. After the concrete is done, put a drain pipe covered with gravel from the back out along both sides to the front so the runoff water coming down the hill has a place to go. Anyway, I called a buddy (also new to concrete) and I rented a couple concrete rakes and an aluminum float. I also told the concrete company when I ordered that I don't really know what I'm doing so please send a driver that will put up with me. My driver was a real nice guy and he worked the chute and gave us some good pointers. I tipped him $25. We just used a long board as a screed and I had watched a video about working the float. My pad came out pretty nice and I watered it every day for a week on the truck drivers instructions. GOOD LUCK!

 

[zeke67]

The first time I was a helper was on a size like that, I think we had four guys of which two knew what they were doing. It was a lot of work. Get more guys, try to find one that has a little experience. Consider the broom finish, how you will edge, do expansion joints, etc.

 

[Vtor]

Prep looks great.

Risk of having to do it again, means I would hire out. It ***** to break apart and dispose if it sets off before you got it right. It's HEAVY stuff.. esp if you are not used to moving heavy AF STICKY shovels full of that magic sauce.

Upside - tons of videos of people doing it with 2-3 people, but STRUGGLING. PROS make it look, just place, screed, float, done - and then the 2 guys pulling screed, 3rd guy making sure it low spots get filled and 4th guy spreading mud head of those 3.

Premix or by the bag ? That's shiiit ton of bags. At 60-80lbs each.

As others said, you need to stake it, or you will end up with a football and not rectangle.

 

[Dig Doug]

Looks great !

a few pointers -
1-
you need more stakes to keep the forms straight the concrete will push out and “BOW “ the forms
at least 4 to 5 stakes at the long side 3to 4 short side use a string line to keep the forms straight - you can push in pull out to keep it in line

2-
is it square measure Corner to corner on the 45 - both dimensions should be the same or really close

3-
when you set up the next section drill in dowels 3/8 rebar drill in about 4 inches, drill holes at a 45 or 22 degree angle about 2.5 inches below top of concrete. this will keep the 2 slabs from lifting or settle down / shifting and will marry the 2 together

note - drilling on the 45 or 22 angle will keep the 2 slabs from pulling apart away from each other.

4-
when pouring the next section dig out under the slab where the 2 slabs meet (**** each other ) looking to under pin so you don’t have a cold joint - less chance for stuff to come in like bugs / water, cracking & shrinking/ expanding during hot/ cold weather wet / dry weather. Concrete moves, cracks and ***** up moisture

 

[welder4956]

Looking good so far. Definitely need more stakes around the perimeter every 2 or 3 feet. The box stores have 1/2" diameter steel stakes with nail holes fairly inexpensive. Bowed forms or a blowout are no fun. You would be surprised how much lateral force the weight of the wet concrete will apply to the formwork.

 

[NDJ]

Well that was a Ton of work !!
I didnt have time to get any action pics unfortunatly. The driver showed up and then it was all a blur from there. The truck was the kind that mixes the concrete components right on the truck and spits it out the back chute. It has this neat remote control console so the operator can stand beside the job and actually drive the truck forward and back and steer , Also can swing the chute side to side and stop/start the concrete flow. Driver was very helpful, Told him we didnt know what we were doing, He gave us lots of advice.

As Zeke and other stated, It was a lot of work for the 2 of us to do the screeding, The driver helped with putting it in the right spot and he had a long "rake" that he used to push the crete around to help us as well. I think it took about 40 mins for us to get it all filled. Once it was filled and screeded he left. I had rented a large Bull Float from home depot and , summoning all my YouTube expertise, went at it. This pic is after the first pass with the bull float. I would soon find the limits of my youtube education though.

About the forms, You cant see in the first pic but there are several 3/4" square steel stakes that I had pounded in spaced along the forms to support them from bowing. I didnt put J bolts in while it was wet, wanted to keep things as simple as possible at each stage, Plan is to drill and epoxy anchors in after its hardened. I do plan to have a row of blocks to form a short retaining wall there where the dirt is high.

 

[Zeke]

Looks pretty good for the first float. You did good for only 2. I'll bet you're sore.

 

[dave*99]

Bravo for forging ahead with only a YouTube education. I did a similar pour for my 12x12 shed 30 years ago. No YouTube, No GJ, put plenty of damn the torpedoes attitude. I had a building permit and they wrote footings required on my sketch. Undaunted, I dug 9 holes around the perimeter with a post hole digger. I did many things wrong. I did not dig out the grass or put any gravel under the slab. My forms were 2x6. I ran short of concrete and had to screed it to about an inch below the form tops. I had one helper. With less experience than I and that's a statement since I had none.

So I floated the slab, pushed some J bolts into it, waited a bit and troweled it and finally put a broom finish on it. Now 30 years later the slab has not cracked anywhere. It is flat and worked out perfectly. Beginners luck was on my side. Got a lot of education that day.

 

[PWC Repair]

Hell YEAH!!! Looks great!

 

[dougf]

Looks fantastic! Great job.

 

[Walkers]

How did the finish come out in the end?

 

[Mainiac Mat]

Nice job. Your prep paid off.

 

[duneslider]

Way to go. One thing I will say that has made a huge difference for me when diying stuff is having drinks and snacks for trades that show up. I feel like people are much more willing to go the extra mile and be more forgiving of your diy experience when they see you care. Gatorade, coke, and dingdongs seemed to go a long ways when contractors or delivery guys showed up.