8in slab vs 4in slab cost?

[Hobby_Man22]

I'd prefer to overdo it than underdo it and regret it later. I may buy a forklift one day. Is there a big difference in cost?

 

[Hobby_Man22]

I want rebar too.

 

[Hobby_Man22]

Oh it's a 50x60 slab

 

[dshop]

why not ask your concrete guy? better than a guess from someone in another state....costs vary depending on location.

 

[PCustoms]

1.5-2.5 times as much.

Double the concrete, not much more labor.

8" is a shitload of concrete, overkill even with a forklift.

 

[Hobby_Man22]

Is 6" more reasonable?

 

[jrsavoie]

I go 5-1/2" rebar. Wire and fiber. 6 bag mix.

 

[SpiderDave]

Yah, 8" is a bit much, if your ground's stable during rainy seasons then 6" would be great, cheaper and plenty peace of mind. If you're talking slab with no foundation around it though, myself feeling the same way you do about doing it right, not twice. Then look into having a bit of a footing poured on the outside edges, maybe 10" give or take? It will help immensely keeping the gravel under the pad. And prevent a lot of wash out that usually happens on flat even pads over time, especially if it's higher than the ground level even by inches or you have a slight tilt to your property where it sits. You'd be amazed how gravel can creep out form under a pad and leave it free standing on the edges subject to damage. Probably one of the most common things I see on slabs, is wash out along the outside edge. It takes time to happen, but it depends on your situation. When we bought our place it had that issue pretty badly in some areas. Even critters used it and started diggin more of it out. I dug it open a bit and pumped concrete underneath and its fine now. But it was a lot of work and could've been avoided. Plus there were no gutters and a slight grade, so that really contributed to my problem before I got here. like I said, it depends on your situation,... just food for thought.

 

[KenC]

Material cost will double. You'll have to talk to the concrete guys about the labor. Placing labor will be more, probably1.5 times, finishing should be the same.

 

[Hobby_Man22]

Code calls for 2ft deep footings around the perimeter and down the center.

 

[Hobby_Man22]

I want to maybe put a vehicle lift in the shop at some point, but don't know where and most call for minimum 8" slab.

 

[mike93lx]

How big of a lift? I would be willing to bet that no lift that isn't made for 15k+ trucks calls for a 8" slab. But it's your money...

 

[Hobby_Man22]

Guess not. Could have sworn I read somewhere of guys making a thicker area in their slab for a lift. Bendpak requires 4.25" slab for a 10k lift. That's all I would need.

 

[finn]

My shop was built probably twenty or more years ago by a guy running a logging business, to keep his trucks (160k loaded weight Michigan trains) in, and repair his skidders, dozers, and loaders.

The floor has radiant tubes in it, and, best I can tell, is four inches thick. It has a few minor cracks over a few of the tubes that are too near the surface, but, in general, is still fully functional.

Eight inches for a home shop is poor engineering, sometimes called overkill by novices.

 

[mike93lx]

Guess not. Could have sworn I read somewhere of guys making a thicker area in their slab for a lift. Bendpak requires 4.25" slab for a 10k lift. That's all I would need.

People do unnecessary stuff all the time

 

[Hobby_Man22]

Wonder why they use such a weird number? Apparently since they use wood for the concrete forms a 4" slab is really 3.5 and a 6" slab is really 5.5" wonder how many people put a lift on a 3.5" slab and call it a day?

 

[beatuptruck]

I have a forklift (9000lbs empty)/. I poured a 5" slab on foam insulation last year (pole barn). No random cracks. (only cracked in control joints.

 

[Hobby_Man22]

9000 pound lifting capacity? Or 9000 total weight? Sounds like you have a little 3500 pound capacity forklift. I think a 5000 pound capacity forklift weight like 10-12000 pounds. It's not really the weight that's the issue its the fact that many have solid tires so all that weight is put in a really small area.

 

[TractorJeff]

6" and service all sizes of Bulldozers on that concrete slab with no cracks. Put in a lift then have thicker pads poured for the posts. Why spend money on too much concrete?

 

[AngryBeaver]

The guy that built my 48x40 poured 6” on the left half and 8” on the right half. He was intending on putting in a 25k pound lift for his dump trucks. I dont know what grade of concrete he used, or what rebar, but drilling it for my 10k lift was the hardest concrete I’ve ever drilled.

way overkill, but I didn’t pay for it. Most 10k lifts require a 4” higher psi and rebar reinforced pad around the lift. 6” is more than plenty for most industrial uses. Our 25k pound komatsu fork truck hasn’t cracked our wash bar where we bring in 20k pound pieces of equipment yet.

 

[Hobby_Man22]

How come I see sidewalk edges and it's like their was a big air pocket when they poured the cement that never got filled so that little section is only like 2" instead of 4"

 

[mike93lx]

How come I see sidewalk edges and it's like their was a big air pocket when they poured the cement that never got filled so that little section is only like 2" instead of 4"

Because not everyone does quality work?

And a sidewalk doesn't have to be super thick

 

[Hobby_Man22]

It was actually a patio for a house.

 

[jrsavoie]

It was actually a patio for a house.

Honey comb? Usually poured to dry.

 

[PoorUB]

One company I worked for built a new shop. 6" slab. It was an HVAC shop and had a forklift capable of lifting 10,000 rolls of steel. So you have a 10,000 pound roll of steel on a forklift that probably weighed 15,000 pounds! No issues with the floor.

 

[rjacobs]

determine where you want your 2 post lift...

install sonotubes 12" deep x whatever diameter you need...

fill with concrete...

Instant spot with plenty of concrete for a lift without spending an extra 20k bucks.


I think for 99% of "home shop" type usage, 4" with rebar or wire mesh is plenty of concrete. How many home garages and driveways you see with broken concrete from being overloaded? Not many outside of **** jobs where the concrete fails.

MIGHT step up to 4k psi concrete as SOME 2 post lifts call for that as a minimum. And obviously a good compacted base.

 

[walrus]

Depends on concrete guy if they are a 2 by 4 for 4 inches slab or they are using form boards that could be 2 by 12s with a chalk line at 4 inches. A properly compacted gravel base is going to be key for putting heavy loads on it. In Maine I wouldn't go under 6" with #4 rebar at 12" inches but that based on my experience with driveway mats in gas stations. I have a rotary lift in my shop with full 6 inch slab with #4 rebar 12 inches on center. Also used 4000lb concrete

 

[HaiKarate]

Pack the hell out of crushed concrete for a base - make your base solid enough and it's almost like extra concrete. I have 6+ inches of packed crushed concrete followed by 6 FULL inches of concrete.

 

[cvairwerks]

One company I worked for built a new shop. 6" slab. It was an HVAC shop and had a forklift capable of lifting 10,000 rolls of steel. So you have a 10,000 pound roll of steel on a forklift that probably weighed 15,000 pounds! No issues with the floor.

It's like where I work...main plant floor is 36" thick, but then we have some equipment that weighs in well over 2500 tons....and used to have a forklift that was rated for 80,000 pound lift at 96" from the mast. The original floor was poured in 1942, and is 300' wide and 1.26 miles long.

 

[dcg9381]

It was actually a patio for a house.

The difference in concrete is just under 50% more (no additional footer depth). Might be some additional digging, so I think 1.5-2.5x is what it should be.

Along with others, I think you're doing it way "overkill" (note I didn't say wrong). I have a 5th wheel and a 1-ton truck on 5" of concrete all day long. I park my cars (including the 6,000 lb truck) on my porch sometimes and frequently use it as a "driveway" to my building. That porch is standard thickness. The only difference is our underlying surface is pretty dense limestone.

I have yet to read of someone needing 8" of concrete. We pour 4.5 - 5.5 inches, use rebar, and we've been good. I have 40,000 lb water tanks sitting on 5.5" of concrete with rebar (note, the weight is spread evenly though). No issues.

 

[bradpac]

I specced a 5" slab based off installation guidelines for a 14k lift. Unless you are doing something really heavy industrial you won't need thicker than that.

 

[Hobby_Man22]

I'll behappy with the 6" slab or 5.5" you're right 8 is overkill.

 

[ZRX61]

At my last place the previous owner had put a 20x30ft extension on the back of the 20x20ft garage. He didn't do anything about the change in grade & just poured concrete to bring it up to level... damn near 25 yards of it.

I should point out that he was an aerospace engineer...

 

[Hobby_Man22]

At my last place the previous owner had put a 20x30ft extension on the back of the 20x20ft garage. He didn't do anything about the change in grade & just poured concrete to bring it up to level... damn near 25 yards of it.

I should point out that he was an aerospace engineer...

well he's got the money then. **** it.

 

[ZRX61]

well he's got the money then. **** it.

That extension cost him $36k, I paid $99k for the garage, house & the 1/2 acre of lane it was on... in 1997.

 

[Hobby_Man22]

I've heard concrete guys like to add water to the mixture to make it easier to work with? I don't understand. Is that so they can spread it easier?

 

[Hobby_Man22]

Every foundation i've seen has had a pump truck that pretty much put the concrete where it needed to be.

 

[Tman]

You drive over 3" thick sidewalks all the time

 

[65ranchero]

2 bay garage 4" of 4000lb concrete w/ rebar ,packed base and radiant heat and a Mohawk 7k lift in one bay
No problem!

 

[Hobby_Man22]

That extension cost him $36k, I paid $99k for the garage, house & the 1/2 acre of lane it was on... in 1997.

Usually cheaper to buy an existing property. That's what I did. Now I'm just adding on to make it suit me better.