Floor Thickness Question/Problem

[romoman]

I had the floor poured for my 24'x36' garage today. It's 3,500 psi with fiber mesh in it and welded wire. It was supposed to be 4" thick everywhere except a 8' area where the lift will go and that was supposed to be 6" thick.

The middle of the floor was a little low and they didn't order enough extra concrete. The floor is 3.5" thick most places and 5.5" where the lift will go. There is a small area (maybe a SF or 2) in the field that is probably 3" thick.

The finish is good and it's pretty level across the whole thing like I wanted. The trucks were on their way, so there was nothing they could do to get more without having a cold joint in the floor. The only real choice I had was to go thinner. I don't want cracks or other problems later. It's going to be a race car shop, so no dump trucks, but jack stands, car dollies with casters, etc.

What amount of problem do people think I have? Something to be annoyed about or fix now? The floor guy said he'd drill holes to check the thickness, but I don't really want the holes in it for later.

 

[BigGarage]

I had the floor poured for my 24'x36' garage today. It's 3,500 psi with fiber mesh in it and welded wire. It was supposed to be 4" thick everywhere except a 8' area where the lift will go and that was supposed to be 6" thick.

The middle of the floor was a little low and they didn't order enough extra concrete. The floor is 3.5" thick most places and 5.5" where the lift will go. There is a small area (maybe a SF or 2) in the field that is probably 3" thick.

The finish is good and it's pretty level across the whole thing like I wanted. The trucks were on their way, so there was nothing they could do to get more without having a cold joint in the floor. The only real choice I had was to go thinner. I don't want cracks or other problems later. It's going to be a race car shop, so no dump trucks, but jack stands, car dollies with casters, etc.

What amount of problem do people think I have? Something to be annoyed about or fix now? The floor guy said he'd drill holes to check the thickness, but I don't really want the holes in it for later.

Besides any other problems that may arise, you didn't get what you paid for. That's a major problem to me. It's not that difficult to figure the cubic yards needed for a project and have enough cement for the job. I would not use a company a 2nd time if they couldn't do it right the first time.

I think you have problems coming in the future with the thinner floor.

Dennis

 

[Ecreps]

I think you will be fine for the most part. Race cars are much lighter than even an average pickup truck.

You may get a couple extra cracks, but as long as you have the minimum needed for your lift I wouldnt stress it too much.

I would try to get some money back from the concrete company though.

 

[Falcon67]

My 2nd truck was late and the first load was setting up. They got it fairly worked out but it isn't exactly flat in places. I had a 12x12 grade beam run down the middle and most of the lift bolts ended up in that. A couple are in 3 1/2~4" 4000 psi stuff. No issues with anything. I put in a 12x12 footer all around plus down the middle and two across - it's settled some in places but over all no real changes from the pour in 2011. Including changes in any normal shrinkage cracks and such. We used 3/8 bar, 24" OC plus two 1/2" bars in the beams.

You can see the grade beam layout here

 

[vavet]

Let's do a little math.
24x36 is 864 sq ft.
You're a 1/2 inch low. 0.5/12 = 0.041 ft.
864 sq ft x 0.041 ft is 36 cubic feet.
There are 27 cubic feet in a cubic yard.
You were shorted 1.33 cubic yard of concrete.
I think most mixer trucks are about 8 cubic yards with some being up to 10?
I'd be really disappointed with my builder and concrete sub.
I guess my actions would depend on a few things. What are the recommendations/requirements for the lift?
What does your contract spell out? Does it specify minimum floor thickness?
If your contract specs it, then I'd have the floor guy start drilling holes. All it takes is one to be under the minimum.
What to do next? If your lift manufacturer only requires 5" or 4" and you're comfortable with what you have in that area, then negotiate for a refund/credit in the amount of a repour. If the lift manufacturer requires the 5.5", then tell them you want it torn out and redone. Maybe you can meet in the middle and they'll repour the deeper section where the lift goes and dowel it in to the thinner sections and get a partial credit/refund for the rest of it where they shorted it.

 

[GMCGarage]

I had the floor poured for my 24'x36' garage today. It's 3,500 psi with fiber mesh in it and welded wire. It was supposed to be 4" thick everywhere except a 8' area where the lift will go and that was supposed to be 6" thick.

The middle of the floor was a little low and they didn't order enough extra concrete. The floor is 3.5" thick most places and 5.5" where the lift will go. There is a small area (maybe a SF or 2) in the field that is probably 3" thick.

The finish is good and it's pretty level across the whole thing like I wanted. The trucks were on their way, so there was nothing they could do to get more without having a cold joint in the floor. The only real choice I had was to go thinner. I don't want cracks or other problems later. It's going to be a race car shop, so no dump trucks, but jack stands, car dollies with casters, etc.

What amount of problem do people think I have? Something to be annoyed about or fix now? The floor guy said he'd drill holes to check the thickness, but I don't really want the holes in it for later.

Im trying to figure out how they ended up at the correct finish floor elevation? I assume the screed boards were set, and the sub grade was set. How did they thin it out, is the slab down 1/2"-1", thus not flat??? Was the sub grade all messed up and thus the 3" slab? Will water pool at the center??

the mesh will help keep cracks closed.

IF the sub grade was compacted correctly, 3" should not be bad, but is not what you paid for.

If need to measure thickness, make them do ultrasonic testing, that way they dont compromise your slab.

 

[Kaizen]

Wtf. My guy was short as I had a thickened edge and he did not order enough. So he ordered another truck and stayed there till 8pm working it. While I don’t think you will have a problem I’d be pissed. Have him half off the price for his mistake


Sent from my iPhone using The Garage Journal mobile app

 

[sz0k30]

I've had a 2 post lift in my pole barn with 3.5" thick concrete throughout for over 10 years now. Never had a problem.

 

[romoman]

Thanks for all the replies!

There is an 8' strip across the 24' dimension that is 2" deeper than the rest of the floor. Last night I went out with a laser and figure that most of the floor is 3.5" thick and there are 2 small areas that probably get down to 3".

The sub grade is very well compacted. I had to dig out a small footer for a the steps and I had to chisel out the sub grade. There is about 2' of 95% compacted base with 4" of compacted 3/4" stone. That is about all on ledge, so the base is really good.

I'm not worried about the lift areas as it's probably 5 to 5.5" thick in those spots. I'm mostly annoyed that they are telling my grade was off in the middle (I had verified the edges were right) and it took more concrete. I told them I bought a 4" floor, not the number of yards they calculated (and didn't measure).

The floor sub called me last night and I stopped before I told him what I really thought. I'm waiting on the foundation guy (who I have to pay) to call me back. I hadn't thought about ultrasonic testing - I didn't like the idea of holes but ultrasonic is good.

 

[NUTTSGT]

Let's do a little math.
24x36 is 864 sq ft.
You're a 1/2 inch low. 0.5/12 = 0.041 ft.
864 sq ft x 0.041 ft is 36 cubic feet.
There are 27 cubic feet in a cubic yard.
You were shorted 1.33 cubic yard of concrete.
I think most mixer trucks are about 8 cubic yards with some being up to 10?
I'd be really disappointed with my builder and concrete sub.
I guess my actions would depend on a few things. What are the recommendations/requirements for the lift?
What does your contract spell out? Does it specify minimum floor thickness?
If your contract specs it, then I'd have the floor guy start drilling holes. All it takes is one to be under the minimum.
What to do next? If your lift manufacturer only requires 5" or 4" and you're comfortable with what you have in that area, then negotiate for a refund/credit in the amount of a repour. If the lift manufacturer requires the 5.5", then tell them you want it torn out and redone. Maybe you can meet in the middle and they'll repour the deeper section where the lift goes and dowel it in to the thinner sections and get a partial credit/refund for the rest of it where they shorted it.

Im trying to figure out how they ended up at the correct finish floor elevation? I assume the screed boards were set, and the sub grade was set. How did they thin it out, is the slab down 1/2"-1", thus not flat??? Was the sub grade all messed up and thus the 3" slab? Will water pool at the center??

the mesh will help keep cracks closed.

IF the sub grade was compacted correctly, 3" should not be bad, but is not what you paid for.

If need to measure thickness, make them do ultrasonic testing, that way they dont compromise your slab.

This and that.

Is the concrete to the top of the forms ? If it is, then there is too much fill inside the forms to get the proper thickness.

 

[romoman]

Im trying to figure out how they ended up at the correct finish floor elevation? I assume the screed boards were set, and the sub grade was set. How did they thin it out, is the slab down 1/2"-1", thus not flat??? Was the sub grade all messed up and thus the 3" slab? Will water pool at the center??

The finished floor is .5" low. The foundation was in and they were pouring the slab to it. They said the sub grade was low in the middle, so it took more concrete. It is pretty level. It's going to rain tonight, so I'll find out if/where it pools. It doesn't have any slope to it, so I expect it will pool.

 

[rburke65]

They should have ordered 2 trucks back to back. Regardless if it’s an 8 or a 10 yard truck, you needed a little more than 10 yards. Should have ordered ..?..7 yards on the first truck, reassessed the coverage, and what ya needed on the second truck PLUS an additional half yard .... everything can’t be graded EXACTLY to 4”.

 

[ConCretin]

The finish is good and it's pretty level across the whole thing like I wanted.

The finished floor is .5" low. The foundation was in and they were pouring the slab to it. They said the sub grade was low in the middle, so it took more concrete. It is pretty level. It's going to rain tonight, so I'll find out if/where it pools. It doesn't have any slope to it, so I expect it will pool.

Sooo, the sub grade was low and they didn't order enough concrete but they realized it before they started screeding and lowered the grade to make up for it?!? That story is BS.

Leaving aside the fact that any competent finisher would order enough concrete in the first place or get another truck if necessary, thinning out the floor is not an acceptable solution.

Will a 3.5" floor perform adequately? Maybe, but that's not the point. You paid for a 4" floor and shouldn't have to accept less because your finisher is incompetent.

I'm not sure what your payment status is but I wouldn't accept what you have.