Help pouring a concret pad.

[JJT]

I did a similar pad a few years ago for a 16x16 shed. I went with a 6" pour, with rebar and no vapor barrier. I'm up north, there are no footers on this slab and there hasn't been a singe crack. I ordered 4000 psi, large aggregate concrete.

Up here the redi-mix companies dump and run, you will not find one that will screed the concrete, that's the contractor/home owner's job.

Make sure you have someone reliable help you out, my help was a no show the day I poured, so I ended up screeding and steel troweling the pad and a 30x8 garage apron single handed.

 

[GareyD]

I live in Bremen, just about 60 miles from you and just completed a 30x50 pour with a steel building...

Here is what I did..

First you need to make sure that any fill you have placed is WELL COMPACTED...this red clay we have around here has a tendency to crust on the top few inches and stay soft deeper down...any movement in the base will show as cracks in the slab...I put the fill in, in 2 inch lifts, drove over it with the tractor many times and water settled it as I went...

I backhoed a 12 inch wide by 6 inch trench 2 inches inside the perimeter and formed with 2x6 lumber...hand dug the last 2 inches out to the form where the overhead doors would be to the width of the door opening plus a foot on either side of the door...tied 1/2 inch rebar in the trench at the door openings, and placed wire on the floors in front of the doors where anything heavy could be parked in the future. Dug 16 inch piers where the uprights of the building would be and placed the bolts for the columns. Used 6 mil plastic vapor barrier (ya know we get a good amount of rain, and clay doesn't drain well around here) didn't want the slab to dry too fast or have moisture wicking in the future.

Poured the slab with fiber reinforced crete, and had the luxury of curing for 45 days before placing any weight on the slab (my building was delayed 3 weeks due to the steel shortage????)

I ended up with a 4+/- inch slab with 6+/- edges...I've parked the L3430 w/BH - the Harley - the boom truck that was used to install the building - my neighbors big ole IH tractor on this slab, that about 90 days later doesn't have as much as a hairline crack anywhere on it...and no I didn't make a single expansion cut on it anywhere...I hate sweeping out cracks!!!

Now I've been told I went to overkill on this project...all the extras...rebar, mesh, extra crete...added less than $500 to the total, but I am fairly certain that I have a building that I can use anyway I want, park anything I'd care to in/on, and not have a problem with for the rest of my life /forums/images/graemlins/smile.gif

Daddy always told me, it's cheaper and easier to do it right the first time, than to have to redo it!!!

GareyD

 

[GareyD]

I got an 8 year old grandson I'd think about rentin' out to you...attached is a pix of him helping float my slab...the big feller behind him is the guy I hired to do the crete work...

GareyD

 

[Junkman]

A contractor friend pointed out to me that a undisturbed pad location is always best. He told me that when doing a shed, or out building that they just remove the top soil and then frame the sides of the pad with 2"X6" or 2"X8" depending on what the owner wants. Put down plastic, wire mesh and drill the outer frame for rebar in the apron area. Then they pour the floor and let it "rest" for a week. Remover forms and backfill to the concrete and never have any problems with settling. He said that undisturbed earth is the best way to do this and having the slab a little higher than the surrounding ground they don't have water problems either. If the "topsoil" is thicker than 3", they remove it and put in stone/stone dust mixture and compact that first. His suggestion to me was to just get the top soil off and not worry about the rest, barring any roots, boulders, etc. This was good advice for me when I poured my concrete garage 6' x 40' apron in the rear of the garage. Not one crack or settling in 3 years...

 

[MFL]

GareyD,

When can I pick him up?? So far the building crew consists of me, Max, my 110lb mutt, whose in charge of pulling out roots, and Hannah, my 35lb mutt, whose in charge of chasing off any dangerous looking rabbits. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

The wife does come out with a cold drink every once in a while and tells me not to come in the house dirty!

 

[MFL]

JJT,

No gravel layer either? Your pour sounds like the perfect answer for me! I'm just afraid that if I don't include some of these other steps, I'll end up with a two piece slab and a crumbling building. This is my first pour of this size, and I'd rather over-build now than live with the consequences.

 

[GerardC]

</font><font color="blue" class="small">( The wife does come out with a cold drink every once in a while and tells me not to come in the house dirty!)</font>

LOL. I wonder if our wives are related /forums/images/graemlins/grin.gif! She will however say that the project looks good though /forums/images/graemlins/wink.gif. G

 

[MFL]

Junkman,

Unfortunately, I didn't have the option to put it in an existing clear area. I cleared a 36x36 area of trees, ground the stumps and am leveling and grading right now. Tomorrow, I'm renting a plate compactor, and shaking my insides lose for eight hrs. getting it as compacted as I can. I'm also driving over it as much as possible with the tractor and letting the un-ending rain we've been having work on compacting.

 

[MFL]

GareyD,

Great Post!! Thanks for the tremendous detail on your project. I hear ya on the properties of Georgia clay!! /forums/images/graemlins/shocked.gif Tomorrow will be spent entirely on compacting!!

 

[mopower440]

..lol..well, maybe finally i can help someone out on this board, about 3 months ago, i was on here asking the same question as i wanted to do as much of the build myself, i am building a 24x30 pole building, what i did was build the frame of the building first, i used 2x6 skirt boards, then i did the floor before putting the metal siding on, i leveled the floor best i could and packed it down by driving the heaviest vehicle i had accross it several times on several different days, then i put down about 3" of gravel, got it leveled out and packed it down by driving over it also, then, i put a divider right down the middle of the barn staked it in with rebar spikes and got it level with the side skirt boards, this way i could do 1/2 of the barn one day and the other half the following week, i ordered #3500 fiber mesh reinfoced concrete, i got 3500 as i would be putting cars on it, if you use the fiber mesh you do not need rebar or the wire mesh..i also got about an inch less gravel around the edges so it would be a little thicker on the edges, the slab is 4" and about 5 1/2 around the edge, the concrete truck came, we had him add a little water to make it move easier, we spread it out with a rented concrete rake and 2 regular garden rakes, we then screeded it from the side skirt board to the center divider i put in, we screeded it 3 times as it would rise a little by the time we would get to the end, after 3 times it looked really nice, we then used a rented bull float and got it nice and glassy looking, then my neighbor talked me into going and getting a broom to put a broom finish on it wich i would have rather left the smooth finish on it, but oh well, it turned out as good as any professional job ive seen and wasnt hard at all, the only hard part is screeding, its not mentally hard, but you will work your butt of working the screed board back and forth, after that was done, we sat back and couldnt believe how nice it looked, we did the following side 3 weeks later, turned out good also, ill tell you this, i was afraid at first, but there is nothing to it, just prepare the ground really good first, get it level and tamp it down the best you can, also, you can use a barrier shhet on the ground before you pour, this keeps a lot of moisture from coming up through the concrete , doesnt make the concrete as cold and damp feeling in the winter..