Concrete Job

[RubenZ]

I seriously don't see what's the big deal here. 8x8 is an easy half day job. Let the guys do it for beer. Just monitor them and ensure they do it right with wire mesh.

 

[litenlarry]

As a Superintendent, used to say to me..You pour water, you PLACE concrete...
Just saying ...Sorta like the "clip/magazine" nomenclature issue..

 

[Watchdog]

I need an 8'x8' concrete pad poured for my garden shed. Estimates are all around $600-$700. Sounds high.

I think before I'd pay $700 for a 64-square-foot slab, I'd sit the thing on two or three 6" x 8" timbers that'd probably last twenty-five or thirty years and forget about it.

And I say three timbers max cause I'd leave the front or back end open so all the little critters could get under it and out of the weather. But I imagine I could get by with just two timbers...so they'd have a front door and a back door.

Plus, I can't abide drunk workmen, friends of friends or not.

But that's just me.

 

[carpriver]

When I was burning wood for heat I would buy a 10 cord load of logs. I would spend my weekends cutting the logs. One summer my neighbor's talked me into the " we'll cut your wood this week end for beer" I agreed butt being fairly smart didn't have the wife get the beer until we were almost done. the friends were a bit upset. They wanted to drink beer and cut wood at the same time. One of the guys had lost half his foot from cutting wood while drinking. Alcohol and work is just not safe

 

[A-37]

Update

The contractor kept scheduling and kept up the no-shows for four months. I finally found a guy who would do such a small job (the 8' x 9' pad). He showed up when he said he would, he marked the area, and came the next day with his crew of 3 and finished the job. The Rubbermaid shed is up and all is well with the world.

 

[litenlarry]

From the first pic, it looks like the mesh reinforcing is on the bottom..It should be in the middle of the slab..Without a chair of some sort to position the mesh, some contractors fashion a hook out of a piece of re-steel to pull the mesh up..Others use the come along and break them..Some better come along rakes have a hook at the top of the blade for pulling up the mesh..
Good Luck, nice looking shed..

 

[BigBoy99]

Wire should be in the middle of the slab..Without a chair of some sort to position the mesh, some contractors fashion a hook out of a piece of re-steel to pull the mesh up..Others use the come along and break them..Some better come along rakes have a hook at the top of the blade for pulling up the mesh.

Totally wrong! The wire mesh needs to be on the bottom of the slab. When there is a load on a concrete slab, there is tension on the bottom and compression on the top. The maximum tensile load is found on the bottom on the slab. Concrete is strong in compression but weak in tension and that is why the reinforcing wire is placed at the bottom. In the middle of the slab is no load, so why would the reinforcing material be pulled up to where there is no load?

I speak from experience as a retired Registered Professional Engineer.

 

[litenlarry]

Totally wrong! The wire mesh needs to be on the bottom of the slab. When there is a load on a concrete slab, there is tension on the bottom and compression on the top. The maximum tensile load is found on the bottom on the slab. Concrete is strong in compression but weak in tension and that is why the reinforcing wire is placed at the bottom. In the middle of the slab is no load, so why would the reinforcing material be pulled up to where there is no load?

I speak from experience as a retired Registered Professional Engineer.

I am not an engineer , but I have placed tens of thousands of cubic yards of concrete..I have never seen wire mesh or other reinforcing that was not embedded in the concrete..
I do not doubt your theory , just not common place the see the reinforcing mesh laying on the substrate..

 

[NYlakesider]

Totally wrong! The wire mesh needs to be on the bottom of the slab. When there is a load on a concrete slab, there is tension on the bottom and compression on the top. The maximum tensile load is found on the bottom on the slab. Concrete is strong in compression but weak in tension and that is why the reinforcing wire is placed at the bottom. In the middle of the slab is no load, so why would the reinforcing material be pulled up to where there is no load?

I speak from experience as a retired Registered Professional Engineer.

Before I was a pipefitter I worked as a union laborer for a few years and poured a lot of concrete. I did both roads/bridges and buildings.

In most cases we had stools that you placed on the ground or bottom of form (Bridge Work or multi story buildings)) that held the mesh up a given amount of space.

PS those bridges I worked on were in the mid 60s and all are still standing and in heavy use today! (upstate NY)

 

[A-37]

I'll defer to the experts on the proper placing of the wire mesh. It probably doesn't make much difference on a lightly loaded pad for my shed unless the subject of frost heaving comes up.

The contractor underestimated the amount of concrete required. After the pour (oops! "placing"), I noticed that the concrete didn't come to the top of the forms which made screeding a perfect surface unlikely. The surface was about ½" below the forms.

I mentioned this to him and his reply was, "Well, you still have a 4" pad." Maybe so, but getting a perfectly level surface when the concrete is ½" below the forms takes a pretty good eye.

Too bad I never learned how to place concrete. Looks like fun.

BTW, the cost of the pad was $700. The Rubbermaid "Roughneck" shed was also $700.

 

[willy]

It's a freaking shed , for goodness sakes. A 4 inch slab will "float", if it isn't connected to something. To stop "frost" heave, you have to put footers down below the frost depth. You don't need concrete footers for a garden shed.

Wire mesh in a slab is not placed to transfer the heat of hydration. It is put there to keep the slab together (in same plane), when it cracks.

A 4 inch slab the size you are talking is only bout .8 cubic yard, and a lot of plants will laugh at you for attempting to order that amount.

Easy amount to pour with 2 people who know what they are doing. Unless it ends up being a hot day and you get a "hot" load let over from another project. Course the driver will willingly remix it "soupy" for ya, kinda ruining the purpose of concrete slab.

As a side thought, sand attracts ants but crushed fine limestone doesn't.

Been in masonry for over 35 years. And instead of repeating good advise I just quoted Zeke.

One more thing ,,the ready mix you get in bags at the hardware stores seem about a 3 sack mix per yard !!!!!
You want at least a 5 1/2 sack or 6 sack mix.(mix is how many 94lbs sacks of Portland cement in each yard of concrete.
For a nice job get 6 sack limestone delivered to you,,, saves the trouble of hauling sand, limestone and cement ,,then cleaning up afterwards.
And don't even think about mixing this amount in a wheelbarrel!!!
Anyone tells you they would mix almost a yard of concrete with just a wheelbarrel ,,has never mixed any amount of concrete before,, or are already drunk.
And no way should you even dream of a pump truck unless you are pouring this slab on top of at least a two story building !!!
Get a price on how much a yard of 6sack limestone costs,, then weigh the cost and your labor to the quotes you have .
It might be worth the $5-$6 hundred to just let someone who does it for a living do it, and save you the hassle.

BTW- the code for frost in Ohio is 40" That means if you want a footer you need to go down 40".

 

[Badquaker]

Totally wrong! The wire mesh needs to be on the bottom of the slab. When there is a load on a concrete slab, there is tension on the bottom and compression on the top. The maximum tensile load is found on the bottom on the slab. Concrete is strong in compression but weak in tension and that is why the reinforcing wire is placed at the bottom. In the middle of the slab is no load, so why would the reinforcing material be pulled up to where there is no load?

I speak from experience as a retired Registered Professional Engineer.

I just happened to take this picture tonight before going home. See those little black stands under the rebar? They keep the rebar elevated during the pour. It is required and part of the pre pour inspection.

I'm sure I can find a lot more of these pics on my phone if I felt like looking. How about I show it in the plans where it's required.

Rebar/wire do not go on the bottom

 

[litenlarry]

I just happened to take this picture tonight before going home. See those little black stands under the rebar? They keep the rebar elevated during the pour. It is required and part of the pre pour inspection.

I'm sure I can find a lot more of these pics on my phone if I felt like looking. How about I show it in the plans where it's required.

Rebar/wire do not go on the bottom

Yep, re-steel chairs...The pic as shown, would be a 2 stage placement..Think of a checkerboard, place the red ones one day, the white ones the next day. Not sure why the edge form on the placed concrete was not removed (pic left)...

 

[Badquaker]

Yep, re-steel chairs...The pic as shown, would be a 2 stage placement..Think of a checkerboard, place the red ones one day, the white ones the next day. Not sure why the edge form on the placed concrete was not removed (pic left)...

I believe you are referring to the redwood expansion joint. Here is a better pic.

 

[BigBoy99]

I was trying to point out that placing of the re-enforcing wire in the center is totally wrong. The wire needs to be at the bottom edge. For increasing concrete strength, having the wire laying on the ground is far better than pulling it up to the center. The chairs in the pictures position the re-enforcing material off the ground but below the middle of the slab.

 

[litenlarry]

Redwood expansion, gotchya ! That appears to be a 6" slab..

On the 4" slab in the OP, when I said pulled up to the middle, I meant somewhere in the middle, not exactly center, but not flat on the substrate..Like I said, I have never seen this done..
I learn something new everyday..

 

[Badquaker]

I learned one third from bottom for vehicle traffic, one third from top for upheaval on interior slabs. Flat against the ground, as in the OPs pic, is never correct.

In the OPs situation, does it really matter? It's an 8x8 shed. I'd be more concerned with it cracking and separating, but that is doubtful at best. I would of had a thickened edge and used #3 rebar, but I tend to over build.

Should the OP be concerned about his wire placement? Not really. In his use, the concrete used and the sub grade prep are more important.

 

[Kid44]

Looks very nice, hope it is big enough, I know how fast those sheds can fill up. Those "I'll put in the shed" can turn into
"I should have put in a bigger shed" pretty quickly.