Insane prices for additional concrete
- Thread starter globalmax
- Start date
That design is not provided in their literature. The pre-existing slab design is incomplete and very wasteful of steel. The "new" retrofit slab is a complete design, but more massive than it would need to be for smaller capacity lifts and monolithic castings.
Sorry for all the crappy answers globalmax. Thickening the entire bay is a waste, and you are still in need of a reinforcement design. If it were my garage I would only thicken the slab near the lift in a capital I or H-shape that tapers to the 4" typical slab. I already designed the rebar for the slab for my 10K future lift, about 9" thick under the baseplates, and the amount of reinforcement is quite low. You could hire a "concrete specialist" as the manufacturers suggest, but they really mean structural engineer. This is such an easy design for us. Too bad the design you need isn't in the lift literature. Call them.
Firebrick43
Well-known member
Who cares? Engineered solutions pencil out in huge projects, not so much in simple residential projects.
So you can spend 1000$ min for an engineer to draw up a solution or waste a few hundred in rebar and concrete compared to a 4" slab with optimised reinforcement and the end result will still work fine.
If the OP was to engineer a change and have the same builders bid it it would result in even more charges than they are already quoting.
Additionally if done as a monolithic pour the slab will almost always crack where the thickness varies. By either doing one whole bay at 6" you are going to only have the crack (hopefully cut in time) where it joins the 4" slab in the other bay. If an H pattern is done you are either going to have to form for it and do two separate pours or live with possibly weird cracking.
Another half baked wrong approach at analysis.
If you hired a professional Structural Engineer he can come up with a thickened slab design just at the posts.
It would not be unlike a reinforced concrete footing for a building column.
Obviously a 2 post lift will have overturning to take into consideration due to potential unbalanced loading so it's not a straight forward analysis for the untrained.
You'd have to weigh the cost comparison of the consultation and reduced thicker concrete area vs just following the manufacturer's recommendations for an overall area approach.
It would not be unlike a reinforced concrete footing for a building column.
Obviously a 2 post lift will have overturning to take into consideration due to potential unbalanced loading so it's not a straight forward analysis for the untrained.
You'd have to weigh the cost comparison of the consultation and reduced thicker concrete area vs just following the manufacturer's recommendations for an overall area approach.
I will add a few things on concrete and reinforcing. I worked in SoCal for almost 20 years and did a lot of concrete So my experience is from that But on the commercial side. I know a little residential from my own remodels and helping friends.
Call out concrete at 2500 psi minimum on the drawings and no inspection is needed. You can place a higher strength and 3000 is a typical as for residential. In the more Recent years concrete has been 3500 and up for commercial structures. Most of the time the 28 day breaks are well over the desired by 800 plus psi.
residential is lucky to get rebar in the slab at at most Is usually 3 or 4 at something greater than 12” OC EW. Wire mesh is the norm for residential. In residential You may see a horizontal bar in a footing or starter wall for anchor bolts and a few verticals but hardly ever cages. Most of the SOG in commercial unless we are reinforcing for chord bars or something in the diaphragm most all SOG have a maximum of 5 bar in them. Usually 12” oc ew but sometimes 8”. Usually 5 to 6” thick.
with that said I do find it odd that the lift manufacturers show the heavy bar for existing sog as I can assure not much SOG is placed like that.
People ask about concrete strength all the time but very few ask for a certain mix design, or review historic data that the batch plant has. strength, Shrinkage, workability, WC ratios. Etc.
Short load fees are high. Even contracting with the batch plant for tens of thousands of yards won’t get you out of them. They will however reduce them.
I do think the 2500 bucks is high but not surprising.
Call out concrete at 2500 psi minimum on the drawings and no inspection is needed. You can place a higher strength and 3000 is a typical as for residential. In the more Recent years concrete has been 3500 and up for commercial structures. Most of the time the 28 day breaks are well over the desired by 800 plus psi.
residential is lucky to get rebar in the slab at at most Is usually 3 or 4 at something greater than 12” OC EW. Wire mesh is the norm for residential. In residential You may see a horizontal bar in a footing or starter wall for anchor bolts and a few verticals but hardly ever cages. Most of the SOG in commercial unless we are reinforcing for chord bars or something in the diaphragm most all SOG have a maximum of 5 bar in them. Usually 12” oc ew but sometimes 8”. Usually 5 to 6” thick.
with that said I do find it odd that the lift manufacturers show the heavy bar for existing sog as I can assure not much SOG is placed like that.
People ask about concrete strength all the time but very few ask for a certain mix design, or review historic data that the batch plant has. strength, Shrinkage, workability, WC ratios. Etc.
Short load fees are high. Even contracting with the batch plant for tens of thousands of yards won’t get you out of them. They will however reduce them.
I do think the 2500 bucks is high but not surprising.
Pretty much every shop with a lift is on a 4, maybe 5" tops slab.
acer66
Well-known member
Why do you think they switched to in ground?
Firebrick43
Well-known member
So they don’t have to pay for door damage when it hits the post.
Cleaner/more professional looking shop
It would be cheaper/easier to install above ground 2 post lifts
Challenger requires the casing to be in the ground at time of pour and 18” thick of concrete around the casing. So how is that “nothing special”?
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firebirdparts
Well-known member
The general consensus was supposed to be that the manufacturer's specification for the floor is adequate.
More concrete does give you something useful, but in a new building there wouldn't be any reason to extend a nice localized bit of overkill to the whole building.
More concrete does give you something useful, but in a new building there wouldn't be any reason to extend a nice localized bit of overkill to the whole building.
firebirdparts
Well-known member
Concrete is a liquid. the extra 2 inches goes into a hole in the ground, and that hole can be made in 10 minutes with a $10 shovel. The benefit of extra thickness is that your pullout force could be distributed into more material. It's only the material in a cone around the bolts that is affected. You deep spot just needs to be a couple of feet wide, where the bolts are.
With a two post lift, the concrete needs to hold the lift down. Holding the lift up is trivial. Even dirt could hold a lift up. for the lift to fall, the bolts pull UP (not down).
Even if that is the case, they are building a house and there are more spaces to put concrete from the second truck
Well, that may not exactly be true. It's going to depend on the design. I don't recall seeing if this is an attached garage, or detached.
If detached, and it's a slab on grade / monolithic slab, your assumption is correct, it's really just a bit more material. But if not, the foundation is poured separately from the floor, in which case, yes you could be in a short load situation.
Not really familiar with typically building standards in your area. Around here, on an attached build, the garage (and basement floor) would be poured separately.
Now, there's also the chance that your contractor is just trying to pad their margin. It's not unheard of for companies to bid low to initially win the job and then charge through the nose for any change orders.
#6 bar 12”OC?, that’ll certainly limit your chances of hitting a bar or two with an anchor
I think the rebar shown in the chart is odd.
Speccing 3/4" (#6) bars in a slab as thin as 4 1/2"??
And the the same rebar size for all slab thicknesses?
I think smaller bars at closer spacing makes more sense with respect to bond development, splices, location in the slab and handling.
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gsmith22
Well-known member
you know what you are doing. some first year out of school came up with the chart so you get nonsensical stuff that isn't buildable.
I don't get all the heartache over the $2500 extra. It may in fact be highway robery for adding the 2" to the slab, but you are building a house. $2500 is a roundoff error in the house construction cost. pay it and move on.
That's scary, isn't it?
I've trained first year graduates in our Engineering design office. They don't know how little they actually know.
The last one quit after six months to go into a sales job when he realized the real world is different that college exercises.
He asked how anyone runs six jobs and trains him all at the came time. The real world....
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On the same note, since the same contractor is doing the whole thing, I'd sit down with him and tell him $1500. No need to pad the pockets of the contractor just because he wants more profit.
These round off's can end up as considerable amount of money eventually depending on the number of changes that happens. Agree that in the big scheme of things, $2500 shouldn't be a big deal.
I am fine with highway robbery. At least both parties know what's going on
What annoys me the most is when someone takes advantage of you just because they are in a position to do it and think that you can't figure it outgsmith22
Well-known member
I'm not advocating that you should just **** it up but you also need to choose your battles. go back to them with what you think is reasonable and have them explain how they got to the number and see what they say.These round off's can end up as considerable amount of money eventually depending on the number of changes that happens. Agree that in the big scheme of things, $2500 shouldn't be a big deal.
I am fine with highway robbery. At least both parties know what's going on
gsmith22
Well-known member
been there done that. someone putting #6 bars at 12" o.c. in a 4.75" slab has never tried to build concrete anything before.
TRWham
Well-known member
I know this thread is old, but somehow I came across it again, and now realize I misread the original post and did not account for the fact this pour was still in planning. Therefore, my reply of some weeks ago was off base and I apologize for my tone, and inappropriate and unhelpful response....
Garage is part of the overall home build considering 4" concrete garage floors. The quote I got for additional 2 inches of concrete is $2500 !!!. Does additional 2" of concreate involve so much additional labor, what am I missing? Guess he is mixing gold hence this price