Foundation Prep with Sod as Fill!

[daveindenver]

Take a look at this foundation prep job for a monolithic slab. Posting just as something to watch out for and/or as a "wow, I can't believe they actually did that" sort of thing. This was done by a local garage builder about 5 years ago. They used hidden sod as fill! I almost cancelled the job when I found this. The owner seemed surprised it happened. They came back and removed a lot of sod from it and compacted it again with another layer of rock over it. If the pour had happened sooner or I didn't notice, it obviously would have just remained. I think it is likely they did not remove all of the organic material even with the fix they did. Makes me wonder if some of the minor cracking I have now is a result of this poor preparation. Most of the cracks are still along the cuts but I think there is some displacement along them also.

 

[dougf]

Wow, that's bad! I would bet this happens more than people think

 

[The Cobbler]

and I wonder if the mesh got all pulled up or mostly laying at the bottom . it should have been on chairs , in my opinion...

 

[pcmeiners]

Wow, that's bad! I would bet this happens more than people think

Worked with a number of contractor, as much as posiible they would bury ANYTHING they could to save on a container......15 years latter a sink hole appears. As long as it does not show up in 3 years, they do not give a ****.

 

[bb29510]

contractor=. con with tractor

 

[Zeke]

contractor=. con with tractor

Very good.

But being a contractor who never had a blemish and very few arguments in 50 years, that's a bit of a generalization and offensive.

 

[NDJ]

"Hire a professional" they said.

 

[NDJ]

and I wonder if the mesh got all pulled up or mostly laying at the bottom . it should have been on chairs , in my opinion...

Watch some vids of the big name concrete guys. They say they pull the mesh up as the concrete is poured using the hooks on the placer tool. Then the next scene you see 2 big guys standing in the crete while they pull the screed board along

 

[Firebrick43]

I was making a delivery to a concrete contractors house the other day. They didn't want my truck on their slab because heavy trucks could crack it? I have seen his work and it never has any stone under it just straight on dirt. Unfortunately many do this because they think that they wouldn't win bids when so many uninformed consumers pick based on cheapest price.. Then they don't bother to educate the consumer.

 

[KEH]

Preparing land for various projects can cause all sorts of problems from unskillful contractors. I worked at a school built in 1936. One day in the 1970s a large round hole developed in the football field after a lot of rain. The principal said the locals said some houses were torn down for the school project and they probably put wood from a house down a well and after so long a time the wood decayed and the top layers of dirt collapsed into the hole. Truck load of soil and some packing solved the problem.
My parents rented a farm with a house back in the 1920s, well included. Many years later house torn down, well filled in. The owner let me cut hay off of the field where the house had been. Sometime after 2000 I was working on the field and dropped a front tractor tire in a hole. The well obviously had been filled partly with wood which had decayed, leaving a 4-5 foot hole. No problem, I was using a tractor with a FEL and pushed the front of the tractor upright and backed a foot or two to get away from the hole.
Cousins clearing some rough land to add to pasture. The man operating a track loader would dump sticks and stumps in little gullys and cover with dirt. Cousin complained after some years that there were holes caused by the wooden fill having decayed and the ground settling down.

Trying to use sod as fill under concrete is a new level of stupidity to me.

KEH

 

[The Cobbler]

Watch some vids of the big name concrete guys. They say they pull the mesh up as the concrete is poured using the hooks on the placer tool. Then the next scene you see 2 big guys standing in the crete while they pull the screed board along

I watched a concrete crew on You tube for a while. they had swelled heads for sure, always on about how good they were, blah blah blah. 99% of their mesh was laying on the base when they were done.

 

[bb29510]

I was making a delivery to a concrete contractors house the other day. They didn't want my truck on their slab because heavy trucks could crack it? I have seen his work and it never has any stone under it just straight on dirt. Unfortunately many do this because they think that they wouldn't win bids when so many uninformed consumers pick based on cheapest price.. Then they don't bother to educate the consumer.

in my area the nearest stone quarry is 200 miles away, so we pour everthing on dirt

 

[The Cobbler]

concrete on solid dirt isn't a bad thing.

 

[Firebrick43]

concrete on solid dirt isn't a bad thing.

Its rarely solid. Which is why nearly every high quality road, runway, or slab is put on compacted crushed stone. The rule of thumb is three times the thickness of the slab but it really depends on traffic, most of the time 2 times is sufficient.

My father tore out a lot of slabs with his excavator and I would load them up in the truck with the loader. I have never seen a slab with a proper base all cracked up. Most of the ones without proper bases were all cracked up. And the wire was always on the bottom unless it was set on chairs.

 

[The Cobbler]

what about footings?

 

[Firebrick43]

what about footings?

They don't have dynamic forces on them and are wide enough to spread the load out for the soil to support them.

You can overcome poor soils with drastically wider footers/rebar also

As you could compensate with thicker concrete and more reinforcement or even grade beams for no crushed stone under a drive/slab but come typically at a much higher cost than stone. Even if you have to haul stone 200 miles, you have to haul it for the extra concrete as well.

They have to be wider in certain soils. Some places need to have crushed stone under them as well. It very much depends on the weight supporting ability of the specific soil. Really poor soils may even require piles driven to better soils or bedrock.



Soil bearing test are done on most commercial jobs to see. Definitely done if soil has been disturbed.

Compacted gravel can support 5000lbs per square foot.

Clays can support less than half of that at around 2000 lbs per square foot or less depending on if a gray clay or a red.

Some precast walls (superior comes to mind) sets the walls on a crushed stone footers.

https://www.concretenetwork.com/concrete-subgrades-subbases/

 

[428PI]

They say they pull the mesh up as the concrete is poured using the hooks on the placer tool.

That worried me when they poured my shed floor but I saw them pulling it up as they went. I believe once they pull it up standing on it isn't going to push it back down any because of the aggregates. You simply can't push it back down. Now, whether it all gets pulled up is another story.

concrete on solid dirt isn't a bad thing

Once my concrete was in my shed I had a little left over limestone that was mixed with dirt in my pile. I had packed in limestone for my shed base. 2 to 3 inches and packed with compactor and sprayed with water and repacked. Seems very solid. Well, I used the left over stuff mixed with topsoil around the entrance and once it rained it soaked it real well and put some hard rock on top of it. Well it felt extremely spongy after that. I ended up removing that **** and filling it in with hardrock. The topsoil we have around here just doesn't work.

 

[strutaeng]

Are you sure that's sod as fill? It looks to me like the grass wasn't removed.

I've seen this done around here on small residential additions, shed/shop pours and stuff like that. Bad practice, yes, definitely.

This wouldn't happen on larger commercial projects with geotechnical report, and engineered drawings, and a testing laboratory. At least I don't recall happening in about 14 years in of my projects.

In certain commerical construction projects like retail interior finish out projects you do have to be weary of contractors that are just starting in commerical. Most come from residential and it can over their head. It really boils down to how good their sub contactors are.

 

[Wrench97]

Preparing land for various projects can cause all sorts of problems from unskillful contractors. I worked at a school built in 1936. One day in the 1970s a large round hole developed in the football field after a lot of rain. The principal said the locals said some houses were torn down for the school project and they probably put wood from a house down a well and after so long a time the wood decayed and the top layers of dirt collapsed into the hole. Truck load of soil and some packing solved the problem.
My parents rented a farm with a house back in the 1920s, well included. Many years later house torn down, well filled in. The owner let me cut hay off of the field where the house had been. Sometime after 2000 I was working on the field and dropped a front tractor tire in a hole. The well obviously had been filled partly with wood which had decayed, leaving a 4-5 foot hole. No problem, I was using a tractor with a FEL and pushed the front of the tractor upright and backed a foot or two to get away from the hole.
Cousins clearing some rough land to add to pasture. The man operating a track loader would dump sticks and stumps in little gullys and cover with dirt. Cousin complained after some years that there were holes caused by the wooden fill having decayed and the ground settling down.

Trying to use sod as fill under concrete is a new level of stupidity to me.

KEH

As a kid I shoveled half a load of dirt out of a triaxle dump that right side tandems sank is a old silo foundation.......................................

 

[daveindenver]

Are you sure that's sod as fill? It looks to me like the grass wasn't removed.

Good question. In some areas, I think you are probably right. I believe I was able to pull out chunks of unattached sod. I bet it was a combination of not removing sod and also using some from the perimeter and high side of the excavation as fill. It is very disappointing when you trust that a respected company will do a job better then you would on something and then end up being let down.

 

[strutaeng]

Good question. In some areas, I think you are probably right. I believe I was able to pull out chunks of unattached sod. I bet it was a combination of not removing sod and also using some from the perimeter and high side of the excavation as fill. It is very disappointing when you trust that a respected company will do a job better then you would on something and then end up being let down.

Ah, ok. Cut and fill. Makes perfect sense.

Understood on the let down. I once hired a painter that did a really lousy job. A bunch holidays and didn't cut-in. I had finish the job myself. It was a homeowner project for myself. Needless to say, I never used him again.

I'm assuming you didn't use this concrete guy again if it was 5 years ago? Did he specifically know and understood the top layer of soil/turf was supposed to be stripped before anything else?

I suppose if there's no specifications then that language needs to on the contract?

Even the good construction companies have their share of their A teams and B teams.