How do I fill a void under my concrete floor?

[b-boy]

When my pole barn floor was added, the concrete guy forgot to add conduit into the garage.

My plumber ran water and conduit up through the floor and had to drill the floor and remove some of the packed stone to make room for the pipes.

Unfortunately, he did a really crappy job of refilling the area. I had some grading done, and the grader was supposed to fix the problem. I just noticed that he did not. He simply piled dirt in front of it. As a result, I still have a void under the floor that goes back to about 6 inches from the edge of the concrete.

It looks like something may have made a home there as well. Probably a rabbit.

My concerns are that my water line will freeze during the winter as a result, that my floor may crack at some point, and that the vermin may start chewing on my water line..

I'm planning to dig it out, evict the critters, and attempt to back fill it with stone.

Anyone have an good ideas for fixing this? Is there any type of expanding foam that might work?

 

[The Cobbler]

maybe call a mud jack ( concrete raising & leveling) company to see what they can do .
or mix up some mortar grout & pack it in there

 

[Bluedodge]

It's not cheap, but Metzger McGuire (the MM80 people) sell this heavy duty expanding concrete filler:

http://www.polishedconcretesolution...MIyZKXiPjC3gIVhZ-fCh3RpA-jEAQYDSABEgIoL_D_BwE

 

[JoeMcGov]

Pressure grout. Foundation rebar contractors tend to be knowledgeable in this process. I'm not saying that it has to exert pressure cuz your situation just needs to be filled. But these type of folks understand the concept.

This doesn't sound like an issue with a DIY solution.

 

[MrSurly]

Get a long funnel with a hose and a bag of "play sand" (clean, fine, DRY sand) OR even better, Portland cement and pour it into the void. Pretty simple stuff. You could also use Great stuff foam.

 

[b-boy]

Get a long funnel with a hose and a bag of "play sand" (clean, fine, DRY sand) OR even better, Portland cement and pour it into the void. Pretty simple stuff. You could also use Great stuff foam.

That's why I asked about the foam. I've seen foam kits that cover a few hundred sq ft. Would something like that actually work? Is it structural?

 

[b-boy]

I like the idea of the portland cement. Easy to fill the hole and then run a hose to get it to harden. Just like a mailbox post. That might work.

 

[b-boy]

I'm pissed because I paid to have this fixed twice.

I called the original plumber back in. He sent a guy who made a half-*** attempt to throw some gravel in there. I gave up on him after a few more phone calls.

The grader obviously tried to make it look like he did it, or just plain forgot. When the animal burrowed into the earth berm you can see that the void is still there.

 

[GMCGarage]

Depends on how big of an area. A few square feet, any foam is going to work and the concrete will bridge over the void. You could try this stuff too, drill a hole and pour it in.
https://www.lowes.com/pl/Fence-post-mix-Concrete-cement-masonry-Building-supplies/4294414304

 

[sreeb]

If this is as small as it sounds, push some dirt in with a stick.

 

[tncatadjuster]

Easy about going overboard if you will ever for any reason need to access it again. I like the play sand covered with a concrete cap that could be removed if needed.

 

[b-boy]

Good point. If I concrete it in, I won't be able to get to it if I have problems.

The void is way bigger than it should be. It's probably 2-3 feet wide.

 

[b-boy]

Depends on how big of an area. A few square feet, any foam is going to work and the concrete will bridge over the void. You could try this stuff too, drill a hole and pour it in.
https://www.lowes.com/pl/Fence-post-mix-Concrete-cement-masonry-Building-supplies/4294414304

That looks promising.

 

[kbs2244]

I like the mud jack co. idea.
This is what they do everyday.

 

[Kevin54]

Pictures????

 

[sstec]

Call around to your spray foam guys. Mine here local has been jacking concrete for years using a different closed cell foam just for sub concrete and can be treated for insects as well.
sstec

 

[wrenchguy]

Shheeesssshhh, the extent of the void is 6" from edge of slab!!! Find some clay and pack it in with a 10 lb. sledge.

BIGGER ISSUE!
"My concerns are that my water line will freeze during the winter as a result, that my floor may crack at some point, and that the vermin may start chewing on my water line..

I'm planning to dig it out, evict the critters, and attempt to back fill it with stone."

Some stone, foam or clay ain't gonna keep that water line from freezing with it being only 6" from edge of slab.

 

[scottydosnntkno]

Two to three feet wide and 6” in? What are you doing putting blocks of steel on every square inch of your garage floor? What will you put against the last 6” that could possibly ever be effected by this.

Get a couple bags of concrete, mix it slightly dry and shove it in there

 

[brewchief]

Look up flowable fill and see if it will work for you, basically a lower strength more easily flowing version of concrete.

 

[Vintage Veloce]

Foam jacking.

 

[In2toys]

I tear out a lot of concrete driveways and garage floors. have yet to see the foam or mud jacking work. if its not structural, id spray foam around the pipes, & then concrete over that to keep critters at bay.

 

[b-boy]

Two to three feet wide and 6” in? What are you doing putting blocks of steel on every square inch of your garage floor? What will you put against the last 6” that could possibly ever be effected by this.

Get a couple bags of concrete, mix it slightly dry and shove it in there

The pipes are about 6" in. The void is wider than that.

My biggest concern is freezing water lines.

 

[b-boy]

I tear out a lot of concrete driveways and garage floors. have yet to see the foam or mud jacking work. if its not structural, id spray foam around the pipes, & then concrete over that to keep critters at bay.

This makes sense. I want to at least get some foam around the pipe. The garage will be heated during the winter (~50F). Obviously, I won't turn on the water until that's in place.

 

[wrenchguy]

The pipes are about 6" in. The void is wider than that.

My biggest concern is freezing water lines.

Did u install frost proof hydrant?

 

[b-boy]

Did u install frost proof hydrant?

At this time, there is just a shutoff valve.

The plumber tapped into my house and ran 1" plastic pipe underground. The water lines are buried below the frost line. The water is not turned on yet. It was installed, tested for leaks, and drained. It's setup so I can drain it from inside my house as needed. There is a foam wrap around the pipe coming up from underground.

My plan is to run water to several points in the building once the building is heated. The plumber assured me that I could run water year round once the building is insulated/heated. I really hope that's the case.

 

[CJseven]

As long as you keep the inside of the building above freezing you can run as many lines inside as you want. Again if you can post pics of the trench area, we could give you much more advice.

 

[b-boy]

At this point it's just a hole in the ground. I'll take pictures this weekend when I excavate the area.

 

[joelmatt89]

Not sure if this is the same situation but I will share an issue I had and what I did. I opened up my floor to install an in ground lift and realized there was an area about the size of a 6'x6' right angle triangle that had a 6 inch gap from concrete to subgrade, the square I cut out just barely ran into this void. It was up in the corner of the garage I think they didn't compact the backfill well and it settled around the house. I also think they poured my garage with like a 7 bag mix or something because the concrete never cracked or even settled and that is right where my front tire sat for 3 years. I am a project manager for a general contractor so I have some good resources and I can borrow any tools I need and get solid discounts.

Anyways say all that to say, After talking with a few guys the solution I came up with was this.

1. Drill 1.5" diameter holes on an approximately 2' grid, if you have the right drill each hole should take about ten seconds... get the right drill
2. The masons have grout pumps that is a basically a 5 gallon funnel with a 1.25 hole in the bottom that runs into a diaphragm pump you pump by hand. These pumps are junk in my experience they never work right. I took the funnel off and bought some tube from home depot with 1.25 id and 1.5 od. Stuff that tube into one of the holes you drilled as tight as possible with at least 3 foot of hose so you can get some good head pressure with the funnel.
3. I used F100 grout which is a very strong grout at $20 per bag that can me mixed flowable and you can add pea gravel to it. mix up 5 gallons at a time and run that down into the holes. Honestly you could probably be just fine mixing up quickrete with some extra water.
4. I then used the handle side of a shovel handle which is a tight 1.5" you can use that to force more material down the holes.
5. Repeat at each hole and use the grout to patch the holes.

Thats what I did you can probably cheap out and use sand or something but in my mind its a lot cheaper to spend a littler more on something stronger and not end up with a slab you need to replace.

 

[scottydosnntkno]

At this time, there is just a shutoff valve.

The plumber tapped into my house and ran 1" plastic pipe underground. The water lines are buried below the frost line. The water is not turned on yet. It was installed, tested for leaks, and drained. It's setup so I can drain it from inside my house as needed. There is a foam wrap around the pipe coming up from underground.

My plan is to run water to several points in the building once the building is heated. The plumber assured me that I could run water year round once the building is insulated/heated. I really hope that's the case.

How close are the lines to the edge of the slab/footer? If it’s just a building on a slab, they need to be as deep as the frost line is into the building because frost can travel sideways under a slab that’s heated above. So in Michigan our frost line is 42”, so the lines under a slab would need to come up 42” in from the wall. If it’s going under/through a stemwall/footer it’s didfrerent because the footer protects it from the frost

 

[TractorJeff]

A piece of 2 inch thick 4 foot wide by 4 foot long foam buried straight down will act as a frost barrier for the pipes also.

 

[b-boy]

I didn't take any pictures, but I dug out the area, used a bunch of spray foam to insulate everything, and back-filled with dirt. The void was about 8 inches high, and about 3 feet across. I filled the entire void with spray foam.

The water line did have foam insulation around it. I'm not sure how much that will help when the temps get below freezing. Hopefully the foam helps. I won't turn on the water until I get the heat running. I'm still working on that.

 

[ammie]

Nice