ANOTHER Slab Question

[plow]

Sorry guys. I know this has been beat to death. I did a search and found a boat load of threads but the amount of info was making my pea brain hurt.

Here we go......

North Louisiana. 39 X 55 slab. Vapor barrier planned. Soil won't be compacted properly (An excavator or dozer will be rolled over it) . Got an estimate for 13K for a 6" slab (5K for dirt work) with footers and two 12" beams running the length and three running the width. Rebar and mesh wire throughout. No mention of the PSI rating.

I have a two ton dump truck and a small Kubota excavator that are the heaviest pieces of equipment that will be on the slab.

The 13K price is more than I wanted to pay. So, exactly what do I need at a minimum to be installed here? I do alot of welding on the ground for larger projects so I need it to be as flat as reasonably possible.

 

[ms fowler]

You are paying $5K for the dirt work. What are they doing for the $5K? Is there any stone going under the slab? At a minimum, I'd want at least 4"-6" of compacted stone over compacted earth. Might be time to get an estimate from another contractor.

 

[Kaizen]

you have an excavator and dump and you're paying someone to do dirt work? might take longer but pretty sure you'll save 4500 bucks

 

[Nexussian]

If the "estimate" doesn't include specifics (PSI, bar sizes & layout, screen size, etc) they are fishing.

A friend that now lives in AZ had that happen on his garage project there in AZ.

He was going to do as much of the work himself as he could.

The "estimate" he got for concrete delivery was 3 times what it wound up costing, after he went through a building contractor.

Said concrete was from one of the companies he got a quote from, when said friend asked about it later the company owner said he didn't know him so he wanted to see how much money he could make off my friend.

The "estimate" or "quote" my friend received was equally vague (no PSI, no aggregate size, etc).

 

[rburke65]

Is it just me or is the above real hard to understand.........

 

[sublimate]

Soil won't be compacted properly (An excavator or dozer will be rolled over it).

Why would you want to pour a slab with the base not compacted properly?
Is failure a good thing in LA?

 

[lakeroadster]

Got an estimate for 13K for a 6" slab (5K for dirt work) with footers and two 12" beams running the length and three running the width.

What are the 12" beams for? Beams buried in concrete?

 

[wssix99]

with footers and two 12" beams running the length and three running the width. Rebar and mesh wire throughout.

Is this a post tensioned slab? If not, what are the beams for? If so, the whole thing is an engineered unit and there isn't much you can do.

I assume it is post tensioned and you need the depth and all the steel to deal with your soil conditions and the lack of a compacted base - but you need to go this way, regardless, depending on the conditions for your area.

 

[Nexussian]

Is it just me or is the above real hard to understand.........

Yeah, I tried to make it clear, but was overly specific.

Point was, without specifics (PSI, etc) it's not an actual estimate or quote.

It would be like asking a fuel company what it would cost to fill your home tank, and them giving you a price without knowing how big the tank is, or what product you wanted delivered.

 

[matt_i]

What's being built on the top, is it a red iron or weld-up building kit? Or stick framed? Reason I ask is if there are any large piers necessary for the column loads.

The basic slab works out to be right around 40 yards of concrete, no grade beams considered. It seems about right to get x + 2x = 3x, where x is the basic cost of the materials, 2x is the cost of labor, and 3x is the total cost.

Digging a bunch of trenches would mess up the ability to compact the soil and add stone because they will be little islands with weak vertical sides.

That said, I do not know your soil conditions. Ask around where heavy equipment is serviced or sold and find out what they did, and try to duplicate that.

 

[brownbagg]

undercut it to natural material, add a foot of sand, vapor barrier and pour on top. do a turn down footer since freeze thaw is less than 3 inches.

 

[plow]

You are paying $5K for the dirt work. What are they doing for the $5K? Is there any stone going under the slab? At a minimum, I'd want at least 4"-6" of compacted stone over compacted earth. Might be time to get an estimate from another contractor.

Digging it about 150' away by my pond.

No stone.

Definitely a 2nd quote. After y'all get me straightened out here, I'll be more informed and know exactly what I need and how to go about asking the right questions.


BTW, the dirt price was a different guy.

 

[plow]

you have an excavator and dump and you're paying someone to do dirt work? might take longer but pretty sure you'll save 4500 bucks

Small excavator. The guy estimated about 550 yards of dirt would be needed. The excavator I have isn't in the best of shape. We mostly use it to load brush on the dump truck. It's pretty weak.

 

[plow]

If the "estimate" doesn't include specifics (PSI, bar sizes & layout, screen size, etc) they are fishing.

A friend that now lives in AZ had that happen on his garage project there in AZ.

He was going to do as much of the work himself as he could.

The "estimate" he got for concrete delivery was 3 times what it wound up costing, after he went through a building contractor.

Said concrete was from one of the companies he got a quote from, when said friend asked about it later the company owner said he didn't know him so he wanted to see how much money he could make off my friend.

The "estimate" or "quote" my friend received was equally vague (no PSI, no aggregate size, etc).

I got that feeling after seeing the Est. Scratched on a pad with a pencil. the only specifics was the size of the rebar (3/8).

 

[plow]

Why would you want to pour a slab with the base not compacted properly?
Is failure a good thing in LA?

Obviously not. The dirt guy said it wasn't needed on a "shop" slab. I talked to a contractor at work and he said that wasn't right.

 

[plow]

What are the 12" beams for? Beams buried in concrete?

For support. I may not be calling them by their right name???? It's like the footer that runs around the perimeter, only through the middle. Think tic tac toe.

 

[plow]

Is this a post tensioned slab? If not, what are the beams for? If so, the whole thing is an engineered unit and there isn't much you can do.

I assume it is post tensioned and you need the depth and all the steel to deal with your soil conditions and the lack of a compacted base - but you need to go this way, regardless, depending on the conditions for your area.

No post tension. Just to be clear, This is a proposed slab. It's not existing.

 

[buckwheat_la]

After reading this thread, my question is "don't you have a building codes inspection agency or some organization that approves plans/set the criteria for these type of things in your area? I could tell you what I think you should do, but it could be completely wrong for your area....

 

[plow]

What's being built on the top, is it a red iron or weld-up building kit? Or stick framed? Reason I ask is if there are any large piers necessary for the column loads.

The basic slab works out to be right around 40 yards of concrete, no grade beams considered. It seems about right to get x + 2x = 3x, where x is the basic cost of the materials, 2x is the cost of labor, and 3x is the total cost.

Digging a bunch of trenches would mess up the ability to compact the soil and add stone because they will be little islands with weak vertical sides.

That said, I do not know your soil conditions. Ask around where heavy equipment is serviced or sold and find out what they did, and try to duplicate that.

Basically red iron. It's a boat load of 4'' square tubing 3/16'' thick I got a screaming deal on that I'm welding into trusses and supports.


Alot of clay with some sand. That said, My sister is building a house a few hundred yards away, she getting soil samples done. Maybe that info could help with this. I'll post them when she gets them.

 

[plow]

undercut it to natural material, add a foot of sand, vapor barrier and pour on top. do a turn down footer since freeze thaw is less than 3 inches.

Say Whaaaaat?

 

[plow]

After reading this thread, my question is "don't you have a building codes inspection agency or some organization that approves plans/set the criteria for these type of things in your area? I could tell you what I think you should do, but it could be completely wrong for your area....

Outside the city limits of a small town in Louisiana. You can do whatever you want (within reason) here. Not saying you can't, but it's not necessary.....Necessarily.

 

[buckwheat_la]

Is the area level? You said it is mostly clay around there correct? If so then you have all sorts of options. 6 inch thick slab means it should support almost anything you want on it (but having the edges thickened to 1ft wouldn't hurt), but I would put pilings down to make sure it doesn't move around though. Not sure why there is 500 yards of earth work that need to be done? But I would pack it down and add a gravel base. If you have more details, I could figure out more for you.

 

[Jess]

To be trouble free, granular fill, compaction, vapour barrier, rebar and 4" concrete of whatever exceed the minimums in your area. Consider insulating the perimeter at the least, to below the frost line.

 

[fastbike02]

When my slab was poured all they did was remove top soil, fill with clay dirt, trench 8" around the outside, and poured 4" thick.... I thought it was little on the weak side but the contractor insured me that for what I had planned that was all I needed. And city approved it all.

 

[lakeroadster]

And city approved it all.

Which means almost nothing. They have no skin in the game, and no liability.

Never ever assume that the city or county approval process acts as a Quality Assurance / Code Compliance check.... 'cause it just ain't so.

 

[ms fowler]

Digging it about 150' away by my pond.

No stone.

Definitely a 2nd quote. After y'all get me straightened out here, I'll be more informed and know exactly what I need and how to go about asking the right questions.


BTW, the dirt price was a different guy.

I am actually going to argue with my earlier post...
IF you are putting this on undisturbed, natural ground ( Not Fill), then you only need to remove the topsoil and organics. You could even leave a trace of organic material so long as it is well mixed into the soil, and doesn't form a solid "mat" of organics.
After stripping the top soil, do a PROOF ROLL. Load up your single axle with as much weight as it can handle, and drive it over the slab area. No turns, just straight across and back. The move the truck over a truck's width and repeat. When you have covered the entire slab area, you will know if you need additional soils work or not. Just look for the deep ruts. If no ruts, you are OK to proceed. I'd put down a vapor barrier, and 4" to 6" of stone. #57 would be good. You might want a final load or two of crusher run (CR6), or even crushed recycled concrete (RC6) if its available in your area.
If you put the vapor barrier (VB) under the stone ( or sand if you choose to use sand), the slab will stay truer to flat than if you put the concrete directly on the vapor barrier. I know most people place concrete directly on the VB, but this forces all the water to go to the surface, rather than drain thru the bottom and the surface. The result is that concrete curls--is higher at the edges than in the middle. Its not really important, but it makes for a better job.

 

[My Old Tools]

What is your soil type. On East Texas sand you can pour a flat slab and it will sit there forever and never move. On black land you have to drill 20' deep piers and set the slab on that our it will break up in 5 years.

 

[buckwheat_la]

When my slab was poured all they did was remove top soil, fill with clay dirt, trench 8" around the outside, and poured 4" thick.... I thought it was little on the weak side but the contractor insured me that for what I had planned that was all I needed. And city approved it all.

Which means almost nothing. They have no skin in the game, and no liability.

Never ever assume that the city or county approval process acts as a Quality Assurance / Code Compliance check.... 'cause it just ain't so.

Respectfully disagree lakeroadster, municipalities have a minimum code to go by because of lawsuits that have happened and studies they have had to have done etc. Because they have no "skin in the game" they usually make you over build not under build things.

I am not saying they don't screw up things, but there are minimum codes for a reason....

 

[wssix99]

For support. I may not be calling them by their right name???? It's like the footer that runs around the perimeter, only through the middle. Think tic tac toe.

No post tension. Just to be clear, This is a proposed slab. It's not existing.

^ Run away from this guy. Far and quick. There should be no reason to build a slab like this. Or put it on uncompacted fill. Or put it on organic dirt. Or slam #3 rebar in there and hope for the best. Even if you had a plan, I'd worry about this guy following it!

Outside the city limits of a small town in Louisiana. You can do whatever you want (within reason) here. Not saying you can't, but it's not necessary.....Necessarily.

You may not need plans or a permit, but I would advise that you go pay a few hundred for an engineer to design your slab/foundation and confirm the sizing of the steel members that you are going to weld together. You are going to spend tens of thousands of dollars on this thing - so spending less than a thousand on a professional who will make sure it won't fall apart or degrade on you is money well spent. (If you don't do this and you plan on enjoying your building for a few years, you'll definitely end up paying less in the end by paying an engineer now.) You don't even need fancy drawings from them! If you can weld and build this stuff, they can just write down the specs for you and your contractors to follow - that's a whole lot better than guessing.

Engineers are trained and licensed professionals - just like doctors. You can pull your own tooth, perform surgery on yourself, etc. - but it's not the best plan. You can get a really bad infection. You don't want your building to be infected by a poor design, either - especially after you set it in stone/concrete.