Concrete Slab-Sea Level

[Richard D]

I hate to start a new thread on a subject that has probably been covered a million times, but I will anyway. I want to pour a slab just under 30' in my back yard to park cars on. There will be a carport over it, but no brick walls, just a fence. I always figured 4" was enough, but my buddy says 3", with 12"(!) deep footings around the perimeter. He is going to be helping me, so I don't want to piss him off, but that sounds like massive overkill. I am down here on the gulf Coast not high above sea level. Frost line is not really an issue here, rarely freezes. What are some guidelines I should follow, or a link I can read?

 

[kd3pc]

quality of the dirt is the biggest question...that is usually what dictates the depth and need for/not a perimeter or more beefy footer/foundation.

Unless he is a soils engineer, I would get one out to give you the real scoop on your soil.

 

[Ole Slewfoot]

they parked this with no footing in 1930. its held up pretty well considering its a cement boat.

https://en.wikipedia.org/wiki/SS_Palo_Alto

 

[Richard D]

Here's another built in 1919, wrecked less than a year later.
https://en.wikipedia.org/wiki/SS_Selma_(1919)

It's kinda spooky driving past it in a boat, or from the ferry from Galveston to Bolivar.

 

[Thumper68]

quality of the dirt is the biggest question...that is usually what dictates the depth and need for/not a perimeter or more beefy footer/foundation.

Unless he is a soils engineer, I would get one out to give you the real scoop on your soil.

Really? A soils engineer for a parking pad, some of you scare the **** out of me.

Anyhow for anything that is going to be driven on I like a thickened edge with rebar.

Plus is you do the thickened edge then if you want to put up a car port later you will be all ready.


Soils engineer

 

[Richard D]

My buddy says I need an edge a foot deep, that seems a bit much to me...what do you think?

 

[Thumper68]

My buddy says I need an edge a foot deep, that seems a bit much to me...what do you think?

That's what I would do, 12" deep 6" wide at the bottom back to 12" wide under the 3 or 4 inch slab, 2 or 3 runs of 1/2" rebar around the entire perimeter.

 

[slip knot]

that's how my shop slab was poured. footXfoot perimeter and 4in thick. I can park a 10K lb tractor on it with no problems. Big picture, that's not gonna add a lot of $$ to the project. overkill is better than underkill???? is that a word???

 

[casmurbax]

that's how my shop slab was poured. footXfoot perimeter and 4in thick. I can park a 10K lb tractor on it with no problems. Big picture, that's not gonna add a lot of $$ to the project. overkill is better than underkill???? is that a word???

I am not an engineer, nor have I stayed at a holiday express...

But I agree with this.

 

[Richard D]

Thanks!

 

[NUTTSGT]

If I was parking a vehicle on a pad, I wouldn't go less than 4" thick, even the sidewalks I poured around the house are 3 1/2" thick.

 

[NelsonLt1]

I'm right down the road in Seabrook, so soil conditions are pretty similar. It sounds like you are pretty much building a driveway without any structure built on it. Correct? Or are you building a carport on the slab?
I just had a 20'x20' garage addition engineered where they are calling for a 2'x1' perimeter beam & 1'x1' cross beam, and 4" thick with #3 on 16" centers. The driveway & patio addition is also 4" thick with #3 on 16" centers, but only needs a 6" deep back cut edge; no beam needed. Hope this helps.

 

[ard]

My buddy says I need an edge a foot deep, that seems a bit much to me...what do you think?

Seems reasonable.

That is 8 inches 'extra'. 30 ft slab, say 12ft deep? So 30+12+30+12=84 ft perimeter. That is 56 cubic feet, 17 cuft in a yard, so two yards of concrete. Plus 84ft of rebar.

For a cost of $200 you will make a bulletproof slab. AND one that COULD then support a shop in the future. Take pictures, document the footer and maybe a GJ member will give you an extra $100 when they buy your place.



(How many times do we read "Ive got a parking slab that Id like to enclose into a shop- what should I do" First question is "dig under the edge, is there a footing?")

Is there ANY chance you'd want to enclose that? Ever?

 

[Richard D]

It will have a carport, which will partly be held up by pallet racks, with steel, lumber, engines, etc. stored away on it. Oh, and a lift. And may be closed in later. So yeah, I guess I need the footers, and a thick beam under the lift. Thanks, my buddy is a lot older than me, sometimes I should just take his advise!

 

[eddieK]

Really? A soils engineer for a parking pad, some of you scare the **** out of me.

Anyhow for anything that is going to be driven on I like a thickened edge with rebar.

Plus is you do the thickened edge then if you want to put up a car port later you will be all ready.


Soils engineer

It definitely depends on the type of soil...expansive soils will destroy it in no time...non expansive not so much. If you are pouring it on sand it compacts nice, but in an earthquake it will roll like swells in a pool.

 

[lakeroadster]

So what are you going to park on it? Just cars and 1/2 ton trucks or maybe some construction equipment, a Bobcat, or ?

What type of lift? Pick a lift and they'll tell you the thickness that is required.

See "Leveling the Site" and "Concrete Slab" here: https://www.garagejournal.com/forum/showthread.php?t=353625

 

[Richard D]

Just cars or half ton trucks. Two post lift, maybe, someday. No heavy equipment. This is my back yard shop, small lot, NOT the house in the avitar picture. 20' wide x 45' long. I do more beer drinking out here than anything else any more...

 

[NUTTSGT]

Seems reasonable.

That is 8 inches 'extra'. 30 ft slab, say 12ft deep? So 30+12+30+12=84 ft perimeter. That is 56 cubic feet, 17 cuft in a yard, so two yards of concrete. Plus 84ft of rebar.

I'm sure just a typo, 27 cubic feet to the cubic yard.

 

[ard]

lol

got the math right though! 27x2=54