8in slab vs 4in slab cost?

[matt_i]

Here is what can happen if your base is inadequate. This is a 7k machine on a 7k forklift.





Part of my shop (pre existing) is 4" thick and my part (which I specifically setup for forklift use and heavy machinery) is 6" thick, both nominal and not trimmed by 1/2" for framing timber. I spent a lot of time working on compacton, gravel base, and a vapor barrier, my part of the shop has #4 rebar on 16" centers in a grid.

 

[zmotorsports]

The pic above is obviously asphalt and comparing to concrete is apples to oranges but in both I suggest getting excellent compaction and even a layer of aggregate prior to concrete.

Sounds like you've already made the decision for 5.5-6 inches which is what I was going to suggest. I poured 6" in my 50x60 shop with about 10 inches of compacted aggregate under that. Mine was designed to hold the weight of a 45' Prevost or Newell coach someday which weigh 52k-55k pounds. I figured that would be the most weight my shop floor would ever have to support and that's a retirement dream. Until then it holds out 40k pound coach perfectly with no issues in the past 4-1/2 years now. I also went with a higher bag mix and extra rebar in key areas such as doorways and approach in the shop with a bit more rebar in the RV bay.

Good luck and make sure to communicate exactly your needs to your contractor or engineer so that they know your intentions and not guessing.

 

[mike93lx]

The pic above is obviously asphalt and comparing to concrete is apples to oranges but in both I suggest getting excellent compaction and even a layer of aggregate prior to concrete.

Sounds like you've already made the decision for 5.5-6 inches which is what I was going to suggest. I poured 6" in my 50x60 shop with about 10 inches of compacted aggregate under that. Mine was designed to hold the weight of a 45' Prevost or Newell coach someday which weigh 52k-55k pounds. I figured that would be the most weight my shop floor would ever have to support and that's a retirement dream. Until then it holds out 40k pound coach perfectly with no issues in the past 4-1/2 years now. I also went with a higher bag mix and extra rebar in key areas such as doorways and approach in the shop with a bit more rebar in the RV bay.

Good luck and make sure to communicate exactly your needs to your contractor or engineer so that they know your intentions and not guessing.

Don't just communicate, get it in writing!

 

[renloy]

And double check how they got everything set up before the pour. If you told them 6 and they set up for 3.5 then you still have time to fix the problem.

 

[KenC]

The base is more important than the concrete thickness. If the base doesn't move (compress) under load the concrete won't crack. If it does move, even slab overkill won't prevent cracks. Well, overkill within reason.

 

[FuzzyTiger]

The base is more important than the concrete thickness. If the base doesn't move (compress) under load the concrete won't crack. If it does move, even slab overkill won't prevent cracks. Well, overkill within reason.

The shop I rent has a 12" slab. This is a garage on a residential acreage not a commercial building. I don't know what the original builder was thinking but the entire neighborhood is built on an active landslide (~1-2 inches/year IIRC) and the garage is the only structure I'm aware of that isn't failing in some way.

 

[PCustoms]

The shop I rent has a 12" slab. This is a garage on a residential acreage not a commercial building. I don't know what the original builder was thinking but the entire neighborhood is built on an active landslide (~1-2 inches/year IIRC) and the garage is the only structure I'm aware of that isn't failing in some way.

12" continuous, or just in the edges?

 

[NUTTSGT]

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

Are you talking about pouring form walls ? A pump truck allows the concrete trucks to pull up to one spot and dump, into the pump truck. The use of a hose/boom from the pump truck allows for a faster pour. Move the hose along the foundation walls with little or no spillage and less work on the guys. Yes, the guy placing the 'crete has to work the hoe but there's no wheelbarrowing dumping or trying to go up a ramp with it.

What the pump truck costs you probably saves you in pouring labor.

 

[FuzzyTiger]

12" continuous, or just in the edges?

Continuous I believe it's pretty absurd but I only rent it, I didn't pay to build it.

Edit: I believe the original owner had some sort of company which produced parts for some industrial facilities. I don't know what exactly but maybe it was to accommodate some very heavy machinery. I vaguely recall Cnc mills can require some seriously thick concrete.

 

[Hobby_Man22]

Are you talking about pouring form walls ? A pump truck allows the concrete trucks to pull up to one spot and dump, into the pump truck. The use of a hose/boom from the pump truck allows for a faster pour. Move the hose along the foundation walls with little or no spillage and less work on the guys. Yes, the guy placing the 'crete has to work the hoe but there's no wheelbarrowing dumping or trying to go up a ramp with it.

What the pump truck costs you probably saves you in pouring labor.

No.im just wondering about when guys like to water down the concrete mixture. I guess They have the cement truck driver do that?

 

[Tman]

No.im just wondering about when guys like to water down the concrete mixture. I guess They have the cement truck driver do that?

Redi mix drivers do carry water. Pretty common to add a little at the site. It depends on what you are pouring, who it finishing it, temps, winds, distance to the pour from the plant etc.etc. Mix design also play an important role.

 

[NUTTSGT]

Redi mix drivers do carry water. Pretty common to add a little at the site. It depends on what you are pouring, who it finishing it, temps, winds, distance to the pour from the plant etc.etc. Mix design also play an important role.

Yes, that's correct.

 

[KenC]

No.im just wondering about when guys like to water down the concrete mixture. I guess They have the cement truck driver do that?

Really common, especially in footings, makes spreading the material easier less rake/hoe/shovel work. All the trucks have water for use in cleanout and will add on request. Usually just a little is needed, but if the job requires a specific slump and too much is added it wall fail a test core.

 

[Showkey]

Really common, especially in footings, makes spreading the material easier less rake/hoe/shovel work. All the trucks have water for use in cleanout and will add on request. Usually just a little is needed, but if the job requires a specific slump and too much is added it wall fail a test core.

Not to mention you pay for specific bag mix say 6 bag or 5000psi . Adding water dilutes and derates the mix.

Link to the consequences of adding water:

https://www.cemexusa.com/documents/27329108/45560536/effects-water-additions-concrete.pdf/277bb588-600b-76b8-a95b-a6e53fad8ff7

 

[rburke65]

I’ve never read where a lift required a floor of 8” concrete.

 

[Hobby_Man22]

You drive over 3" thick sidewalks all the time

Huh? Since when? I see tons of driveways that are cracked up. Still functional but not acceptable for a slab.

 

[Hobby_Man22]

I’ve never read where a lift required a floor of 8” concrete.

They do but it's like a 20k lift and nobody needs more than a 10 or 12k for a diesel pickup.

 

[egdede]

And that's what the aerospace engineer did, modify an existing property. He just used too much F'n concrete!

 

[Tman]

Huh? Since when? I see tons of driveways that are cracked up. Still functional but not acceptable for a slab.

At least in the Midwest the residential sidewalks are layed down before driveways are poured. 2x4 forms and pour away. It gets driven over every time you enter and leave the driveway.

 

[Hobby_Man22]

At least in the Midwest the residential sidewalks are layed down before driveways are poured. 2x4 forms and pour away. It gets driven over every time you enter and leave the driveway.

Not here. If there is no house on the lot you either walk in the grass or on the street. Who would put a sidewalk through a driveway? That looks retarded. Lol

 

[Tman]

Where I grew up. 2nd from right, notice the sidewalks continuous and the drive and approaches were poured later?

 

[mike93lx]

Not here. If there is no house on the lot you either walk in the grass or on the street. Who would put a sidewalk through a driveway? That looks retarded. Lol

Where the hell else would you put a sidewalk? Not like it can be a bridge over the driveway or a tunnel under

 

[billconner]

Side walk is usually on municipal public land and the driveway is yours. Sidewalk might be there long before house, at least where I have lived.

 

[78SC4X4]

Please read this, follow and be happy........... https://www.garagejournal.com/forum/threads/the-concrete-undergrounds-guide-to-floor-slabs.382626/