Anchor depth

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I’ve recreated the image provided by @Dicer back in post #63

The total volume of a pit matching these dimensions would be 21.856 cubic feet (per pit so x2)

since each cubic yard of concrete contains 27 cubic feet, I would need to order 2 cubic yards.

I’ve been quoted $158.00 per cubic yard of 5000psi concrete mix. With a $100 delivery fee for orders under 5 yards.

$416.00 for the cost of concrete Through a concrete supplier

ordering it through the supplier would be cheaper than doing bag by bag and having to mix it myself

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68gtxman said:
Frost heave. This is down below the frost heave depth, if you need to worry about that. Otherwise, it’s not needed.
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Ah ok

I live in North Carolina. Coldest it gets in my area is occasionally in the single digits. With very little snow. Would that design without the column be ok? And if so, would I still need the vertical rebar inserted into the floor of the pit?
 
This is just insurance.... cheap insurance. I do not know what you have under your cement, rock, dirt, sand, slit or river rock? Adding an extra 18" column will help the block sit flat if there is a tilt situation on car lift loading....nothing more...nothing less.
 
Dicer said:
This is just insurance.... cheap insurance. I do not know what you have under your cement, rock, dirt, sand, slit or river rock? Adding an extra 18" column will help the block sit flat if there is a tilt situation on car lift loading....nothing more...nothing less.
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makes sense. An 8” Diameter by 18” column doesn’t use much concrete. Hell I’d probably make the column 12” in diameter
 
Another question, my slab is on a thick layer of large gravel. The outer walls of the slab are 8x16 block. Since the slab isn’t over soil, would adding these large pads pose a problem/ would they be more prone to shifting? General location of new pads circled in red.

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Evan Dutch said:
Another question, my slab is on a thick layer of large gravel. The outer walls of the slab are 8x16 block. Since the slab isn’t over soil, would adding these large pads pose a problem/ would they be more prone to shifting? General location of new pads circled in red.

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You are asking a question that most attorneys would never answer more than “it all depends” in response. Was the ground under everything flattened and leveled out before the gravel was placed? Was the ground then compacted with a vibratory plate compactor? What kind of gravel was used (river rock, graded, mixed crushed, etc)? How was it placed? Was it compacted? And possibly other questions.

I would say that you already made the call to place what you’ve placed and there it is now. If anything you did was incorrect, then the building/slab may shift or tilt. If it was mine, I wouldn’t mind slight movement of it anyway. Many smaller metal and wood buildings are placed now without much consideration of frost depths (I.e. footings below the frost depth) and they may rise and drop a little as the subsoils freeze and thaw. Adding the new footings that you are doing for the lift will act to solidify the rest of the slab from side movement - they will act like anchors if nothing else. They certainly won’t make anything worse.
 
68gtxman said:
You are asking a question that most attorneys would never answer more than “it all depends” in response. Was the ground under everything flattened and leveled out before the gravel was placed? Was the ground then compacted with a vibratory plate compactor? What kind of gravel was used (river rock, graded, mixed crushed, etc)? How was it placed? Was it compacted? And possibly other questions.

I would say that you already made the call to place what you’ve placed and there it is now. If anything you did was incorrect, then the building/slab may shift or tilt. If it was mine, I wouldn’t mind slight movement of it anyway. Many smaller metal and wood buildings are placed now without much consideration of frost depths (I.e. footings below the frost depth) and they may rise and drop a little as the subsoils freeze and thaw. Adding the new footings that you are doing for the lift will act to solidify the rest of the slab from side movement - they will act like anchors if nothing else. They certainly won’t make anything worse.
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the block walls sit on concrete footings all the way around. The ground under the gravel beneath the slab slopes toward the back (shallow at the front and deep towards the back) on top of that sloped dirt is gravel (mixed rock) that Is leveled to approximately 4in below the top of the top layer of block. So I’d image there was more gravel needed in the rear of the slab to backfill in Order to completely level the rock

essentially I’ll be digging through what I believe to be a good bit of rock before I hit dirt when pouring these footers.
 
Evan Dutch said:
the block walls sit on concrete footings all the way around. The ground under the gravel beneath the slab slopes toward the back (shallow at the front and deep towards the back) on top of that sloped dirt is gravel (mixed rock) that Is leveled to approximately 4in below the top of the top layer of block. So I’d image there was more gravel needed in the rear of the slab to backfill in Order to completely level the rock
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How deep are the perimeter footings? Are they below frost depth? Are their bottoms all on the same plane and is that plane level?
 
68gtxman said:
How deep are the perimeter footings? Are they below frost depth? Are their bottoms all on the same plane and is that plane level?
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I believe the footings to be 14in deep below the soil on both sides and the rear wall. The front wall is much deeper. Closer to 3ft below the soil. When the inspector looked at the front footing he said the soil may be “soft” so he asked for a deeper footing. As far as being all the same plane, They’re probably not 100% this was all done to local code as the entire build was permitted (I know code varies per location)
 
Evan Dutch said:
I believe the footings to be 14in deep below the soil on both sides and the rear wall. The front wall is much deeper. Closer to 3ft below the soil. When the inspector looked at the front footing he said the soil may be “soft” so he asked for a deeper footing. As far as being all the same plane, They’re probably not 100% this was all done to local code as the entire build was permitted (I know code varies per location)
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Then everything should be A Okay. Proceed without worry.
 
JDMopar said:
With all the figuring and worry you're having to go through, I believe I would sell that 2 post and buy a 4 post!
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I don't think he's worrying at all. He's simply researching something he's not as familiar with as some of the folks on this site who have obviously done this type of work for a very long time. It's not a huge job, but definitely something one wants to feel comfortable with when it's done.
 
JDMopar said:
With all the figuring and worry you're having to go through, I believe I would sell that 2 post and buy a 4 post!
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I’ve used 4 posts and 2 posts. With the limited space in my shop I feel a 2 post would be best. I don’t mind a 4 post, but I feel things under the vehicle are more accessible when using a 2 post lift. This is just my opinion though. Also if need be I can remove car and truck bodies from their frames using a 2 post.
 
Yeah....I agree about the amount of room and better versatility of the 2 post. I was just making a random goofy comment...lol. You're doing the right thing by getting lots of opinions on how to go about it. I don't even pretend to know anything about engineering, but I would think that the farther down you extend the round vertical section of concrete and rebar....the less likely the lift would be to lean forwards or backwards because of an imbalanced load. I guess you could do the same thing by making the new concrete pour for the lift H shaped....but that would be Mo concrete and Mo money! :eek:
 
JDMopar said:
Yeah....I agree about the amount of room and better versatility of the 2 post. I was just making a random goofy comment...lol. You're doing the right thing by getting lots of opinions on how to go about it. I don't even pretend to know anything about engineering, but I would think that the farther down you extend the round vertical section of concrete and rebar....the less likely the lift would be to lean forwards or backwards because of an imbalanced load. I guess you could do the same thing by making the new concrete pour for the lift H shaped....but that would be Mo concrete and Mo money! :eek:
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Yeah I gotcha, trying to minimize the amount this will cost without half-assing it. Over $400 for concrete alone. Not including rebar, and saw rental. I’ll probably dig out and finish the concrete myself so I can save money.
 
Dicer said:
What ever became of this project?
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After much deliberation I decided to follow the factory manual (which recommended a minimum of 4inches of concrete for the anchor install) and drilled into my preexisting concrete to install the lift. While doing so, I measured each hole to ensure correct depth. All the holes were over 4inches in depth. I installed the anchors and torqued them to spec. I had to loosen and re-tighten multiple times while I was shimming the columns to make them level. The lift has been up for a few months now, the largest vehicle I’ve had on it is a newer 4 door 4wd Toyota Tundra. I followed the manual and checked the anchor torque every so often (which reminds me I probably should check it this weekend). It’s definitely a nice thing to have, as soon after I installed it I had to install a clutch in one of my cars, and a transmission in two other cars. As well as another one of my cars needing a clutch soon.
 
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