Decided to build a garage. Now the fun begins.

[GrimsterGMC]

It was pointed out to me that the contractor backfilled the hole left by the stumps with dirt, some of it topsoil.

The first contractor said he would backfill the holes with gravel. I thought this guy was going to do the same, but he apparently meant to add gravel to the top to make up for the volume left by removing the stumps.

Now I’m concerned about compaction in the filled area. I feel that I should have said something while he was doing the work, but I didn’t, as he seemed to know what he was doing.

I plan to have a conversation with him today to share my concern and see what the options are.

Worst case would be digging it up, hauling off the dirt, and backfilling with gravel.

Am I overthinking this?

It's easy to get caught up in the moment and not see things straight away. Best to question it now while it is easy to rectify.

 

[South VA]

It's easy to get caught up in the moment and not see things straight away. Best to question it now while it is easy to rectify.

You’re correct. This has been on my mind a lot. And, as if to confirm my concerns, a couple of days ago another neighbor mentioned that he’d built a garage under similar circumstances, and had his slab settle 6” in the first six months.

I finally spoke with Steven today and expressed my concerns.

He took it well. He confirmed that he compacted the dirt with the machine in 1 foot lifts, which is good. But he said that to minimize settling when using soil for backfill, ideally it should be allowed to sit for a few months.

However, we don’t have that much time, as our lock on the building price will expire and it will be adjusted to the current market rate. Also, even after letting it sit, there’s still a chance of the slab settling.

He talked about adding rebar to the section over the hole, but that seemed to be a stopgap measure.

He then brought up the idea of digging the dirt out of the hole and replacing it with gravel. This is actually what should have been done to begin with. I had mistakenly assumed that he planned to do that, as the first contractor had planned to do. But he didn’t, and his bid did not reflect that amount of gravel. That’s on me.

The result of this conversation is that he’ll dig out the dirt, haul it off, and replace it with gravel. That is exactly the solution I had in mind, and it was good that he came up with it on his own. Ok, maybe with a little prompting.

It will add to the total cost, but not unreasonably so. The end result will be worth it, and I won’t have to worry about it anymore.

Steven said that we’re still on schedule to have the slab poured by the end of the month or the first week in November.

Seems like progress.

 

[GrimsterGMC]

That's a good outcome, and he is aware you are both knowledgeable and willing to question things so he may be more careful in future. I have been involved in the building trade for many years and seen things go south very quickly when either party isn't respectful to the other but you have handled this well.

 

[South VA]

That's a good outcome, and he is aware you are both knowledgeable and willing to question things so he may be more careful in future. I have been involved in the building trade for many years and seen things go south very quickly when either party isn't respectful to the other but you have handled this well.

Thanks. It feels like a good outcome. I’m relieved to have that particular issue resolved, as it had potential for significantly affecting the overall project.

And, of course, I’ll be on hand to watch the excavation of the dirt, backfilling with gravel, and hauling off the excess dirt. If I see anything that concerns me during that process, I’ll address it at that time.

Lesson learned.

 

[Rock Hard Concrete]

I am sorry I am not in your area. We would have had this taken care of for you in a couple of weeks, properly. A couple of notes since I haven't been keeping up on the thread,

4000 psi (6 sack) concrete when properly placed will hold a fully loaded concrete truck without cracking at only 3.5 inches thick. If you are planning on a 4 post car lift then 4 inch will do it, a 2 post car lift will require 6 inch just so the anchors can bite deeper since there is radial load on the fasteners with a 2 post lift.

Rebar does not prevent cracking. Rebar prevents settling and separation of cracked concrete, bit do not ever think it prevents cracks. It actually gives the concrete a void. I recommend your contractor use fiberglass non-corrosive rebar. It is the size of 3 bar (3/8) but it is stronger than 4 bar (1/2). Have your contractor use fibermesh reinforcement if you want to prevent cracks. But by far the most important thing is ground prep. 3.5 inch unreinforced concrete will live longer if the ground is prepped correctly than 6 inch reinforced concrete will over crappy ground.

 

[Erik the Awful]

Most two post lifts spec 4" thick, but I spec'd two 6" deep 4'x4' pads where I want the posts set. Some day.

Years ago when I was a dealer tech, our dealership moved into an old dealership lot that didn't have lifts. Our manager got lifts installed, but about 6 months in one of my coworker's lifts began pulling the anchors out of the concrete. Come to find out the slab in that area was only about 2" deep. To solve it they dug out a 3'x10' trench and filled it in with 6" of concrete and anchored the lift onto that. I'm not sure that I like that resolution, but it worked.

 

[South VA]

I am sorry I am not in your area. We would have had this taken care of for you in a couple of weeks, properly. A couple of notes since I haven't been keeping up on the thread,

4000 psi (6 sack) concrete when properly placed will hold a fully loaded concrete truck without cracking at only 3.5 inches thick. If you are planning on a 4 post car lift then 4 inch will do it, a 2 post car lift will require 6 inch just so the anchors can bite deeper since there is radial load on the fasteners with a 2 post lift.

Rebar does not prevent cracking. Rebar prevents settling and separation of cracked concrete, bit do not ever think it prevents cracks. It actually gives the concrete a void. I recommend your contractor use fiberglass non-corrosive rebar. It is the size of 3 bar (3/8) but it is stronger than 4 bar (1/2). Have your contractor use fibermesh reinforcement if you want to prevent cracks. But by far the most important thing is ground prep. 3.5 inch unreinforced concrete will live longer if the ground is prepped correctly than 6 inch reinforced concrete will over crappy ground.

Thanks. It’s an unfortunate fact of life out here in the sticks that concrete contractors, especially good ones, are few and far between.

Steven is a young fellow, and as such hasn’t accumulated the experience that I would prefer, but he seems to be pretty conscientious and capable of doing a good job. He was recommended by a trusted general contractor who used Steven on his own residence. I got the sense that his mention of adding rebar was more thinking out loud than a serious suggestion.

The solution proposed and agreed to - digging the hole out and replacing the dirt with gravel - seems like the only way to effectively deal with this particular situation. As a result, the slab will rest on a combination of undisturbed ground, with a layer of gravel, and the aforementioned hole backfilled with gravel.

The slab will be 4” thick, at 3000psi. He’s using a fiberglass product that is mixed with the concrete, and rebar around the perimeter for the thickened edge, according to the spec provided by the building manufacturer.

I had been considering a four post lift, but have decided on a two post lift. The slab will be at least 6” thick in that area.

 

[62barsoom]

I am sorry I am not in your area. We would have had this taken care of for you in a couple of weeks, properly. A couple of notes since I haven't been keeping up on the thread,

4000 psi (6 sack) concrete when properly placed will hold a fully loaded concrete truck without cracking at only 3.5 inches thick. If you are planning on a 4 post car lift then 4 inch will do it, a 2 post car lift will require 6 inch just so the anchors can bite deeper since there is radial load on the fasteners with a 2 post lift.

Rebar does not prevent cracking. Rebar prevents settling and separation of cracked concrete, bit do not ever think it prevents cracks. It actually gives the concrete a void. I recommend your contractor use fiberglass non-corrosive rebar. It is the size of 3 bar (3/8) but it is stronger than 4 bar (1/2). Have your contractor use fibermesh reinforcement if you want to prevent cracks. But by far the most important thing is ground prep. 3.5 inch unreinforced concrete will live longer if the ground is prepped correctly than 6 inch reinforced concrete will over crappy ground.

Would fiber added to the mix help? 10' lifts compacted with a jumping jack? Oh I'm jealous of your new space.

 

[Rock Hard Concrete]

Yes fibermesh is always a great idea. The best is to use fibermesh with rebar that way you have the crack resistance of the fibermesh with the settling/separation resistance of the rebar.

 

[62barsoom]

Yes fibermesh is always a great idea. The best is to use fibermesh with rebar that way you have the crack resistance of the fibermesh with the settling/separation resistance of the rebar.

I had always just told the dispatcher to add fiber, didn't realize this what you meant.