Concrete Slab Prep How Accurate

jmacd

I do quite lot of slab prep work for others and would like to know what you guys think is an acceptable percentage off on concrete usage. Here is an example: the last one I did was 2000 sq ft 8" of concrete.

My math is 49.38 yards and add 5% for waste you got 52 yards. The GC said the mason "said" he used 5 extra yards ( he didn't give my the total yards used) and billed my back for 1/2 of the cost. A couple of lessons learned here, correct me if I am wrong or you guys have a better way.

I will check grades with mason or paver on every job before they start the next step and have them approve grades before I leave.

What is the acceptable overages you guys live by? I lived by 5% so in this case if the mason was telling the truth I was 10% over and paid for 5% of it. Again if I pulled strings with the mason before he set up his forms I could of eliminated this.

The thing that kills me is this, I had crusher run on site but as soon as I backed my roller of the pad the mason was setting his forms before I could even shut my machine off, this will never happen again. I ended up trucking the extra crusher run away. Couldn't you loose 5 extra yards in the truck or the pumper or hose etc. ? I could of been 1/2" under and that would account for the material, my roller will compact about an 1" at least.

How do you protect yourself from this do you have a clause in your contract?

user50444

first off, who's to say he wasn't higher then what top of concrete... you can be off +1.5 yards on that size if he was up a quarter inch on average...? Just a thought.
Any body I've ever been around that pours + my company, it's always up to the concrete contractor to finalize grade + compact. An excavator gets as close to grade as possible from what homeowner or general sets as that to be. We always set top of concrete with pins, grade down to our thickness of concrete + strike with 2x4 which ensures proper thickness expected. Usually leaving a 1/2" high for compaction (pending subgrade material).
So for acceptable amount,... it shouldn't even be your situation.
In contract,... rough grade + leave a few yards of material on the side for them to use if needed.

Little

Did you grade it once and let it be? All my concrete work i will grade as accurately as possible, compact and recheck, then fine tune my cuts and fills. We just did a huge concrete truck turnaround and made sure we were close to spot on. We only prepped subgrade and concrete contractor came in and the pour. They ended up going 60cy over and tried to blame us. We as-built the entire pad and they were averaging an 1" to 1.5" high everywhere from the proposed grades. And yes 5% is an average waste number.

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jmacd

Little, actually we had it up to grade that was set by GC and then GC changed grade to make one side an 1'' higher so he could do his asphalt easier. We stayed late that day till dark and added close to 30 tons of material and had it finish graded again with strings and pins and compacted so I doubt we were off very much to Begin with.

We also completed our work a day early so his mason could do his work because "this was the only day he could do it" crap. My question is how many run into this and how do they protect themselves from getting caught up in this for the future.

My best solution is check all grades with paver or mason before you pull your equipment out. I think the GC was screwing with me but just wanted to confirm and learn.

JDavis21835

I just did an 8,000 sq ft building in the last week. Walls were poured, afterwards we graded for the slab. I placed sand in at actual floor grade, then compacted. Afterwards I cut to subgrade. I tend to undercut myself, so I have my ground guy fool me but having me 1/2 to 3/4 inch high. This usually puts me about 1/4 inch high. Concrete guys came in behind me, drug the track marks with their come alongs. Got big kudos from them, as they were expecting everything to within 6 inches. Apparently a few of our other operators think +-6 inches is close enough.

Common practice around here is +- 1 inch. The final is usually up to the concrete crew.

neolitic

I think I'd ask to see his delivery
tickets before I ate the back charge.

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jmacd

jdavis, that's number is what I have used in the past +/- 1" .
Apparently on this job 1/2" with in grade wasn't good enough so from what I have been told this GC was just asking more than what was reasonable.

I accepted the deduction but didn't like it much and will remember this experience on the next one we do for this particular GC and others. I have never had the concrete crew come in and regrade any of my past work, and they didn't this time either.

It appears to me from past experience that the GC expects it in be perfect and no extra material to used or a deduction will be made from invoice to cover cost of material.

Maybe in the future I will finish grade a 1/2" high. I definitely will check final with concrete guys before I commit to be done. Just venting again but I can't be the only one that had to deal with this. As usual I have learned a lesson the hard way.

jmacd

Neolitic, I questioned it when we spoke on the phone before check was sent out and he said " what you are saying is mason lied". GC got all defensive so I backed down because deduct was $275 and I am trying to build as large of a customer base as possible.

Some day I hope I work for the guys that I want to work for not the guys that I have to work for.

I am still a long way away from that at this point. My lessons always are learned the hard way.

jmacd

What do you do to protect yourself on this one.

JDavis21835

You have learned what a lot of us have learned. High is good, low is bad. I try to do that with not only concrete, but also paving contractors.

jmacd

I have 22,000 sq/ft parking lot to prep for next week so I can promise you, high it will be.

Little

Yes forgot to mention i def keep everything on the high side myself.

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tgeb

It's not that he lied, but that you need proof of excess material used on the job. If they cannot provide documentation.....why should we pay?

I can provide delivery tickets for all of my concrete orders, going back years. It should not be an issue.

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www.gebcon.com

neolitic

Hmmmmm, and the mason says your work
was bad.
He said, she said....
"Show me the money!" (In this case the paper)
I hear you about not wanting to tick him off,
but he should know that you aren't up for
being walked over too.

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cexcavation

The concrete contractor vs. excavation contractor battle is prevelant around here too!! The thing that I have found with concrete guys is that they want to charge a large some of money while leaving their shovel and rake on the side of the truck just for looks. I can nail smaller pads down to within plus or minus 1/4" overall, but I guarantee that there will be a few minor high spots that are inevitable unless you run a screed board across the entire pad.

Now using this small pad as an example, I say it is plus or minus 1/4" which is darn good for us toothless degenerates who play on equipment for a living All of a sudden, according to a concrete guy, this same pad becomes 2" out of grade based on two things. One-The concrete sub does not own a laser transit and therefore uses bowed form boards and 4' bubble level that doubles as a digging tool. Second-The concrete sub walks out on the pad and finds the one knob on the outer edge of the whole pad that I failed to hit with the laser. From there, he builds his forms and doesn't realize that everything else is consistently 2" above prep grade.

Don't worry JMACD, concrete guys are good at pointing fingers to cover the fact that their own prep work is horrible Ever go by a project that is prepped by the concrete guy's themselves and you'll understand the term "close enough". Around here, we usually leave the grade a touch low, have some gravel on site, and tell the concrete guy's to set the final grade once they have there crooked forms in place. If I prep for private people, I nail it right down. Point being, no matter how level you make a pad, the concrete guys are bound to screw it up with their forms and interpretation of the plans. One last thing to realize is that many concrete subs that have lasers more than likely do not have them re-calibrated/checked very often. Lasers do get off just the same as levels and therefore the margin of error has to be taken into consideration.

I personally would not have paid for the extra concrete based on the reasoning that one phone call would have gotten me on site to correct anything that was my mistake prior to the pour. Once the mud is on it's way, the concrete sub is essentially stating that the prep was good enough to pour on and therefore they pay for any overages. If they were in too big of a hurry to call you, then it must be worth the extra $275 to push forward. Just my opinion.

JDavis21835

For all the reasons Cexcavation lists, I am really glad we have our own concrete crew following us.

joasis

Yes, and, you are not responsible anyway...you didn't set the forms. If he ran them slightly high, it isn't your problem...if he shot grade correctly, and he needed you to be closer, it was on him to say something.

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Framer53

I have always asked a GC to proove any backcharge. It is my money after all.
Be firm but polite in questioning. It sounds like you might have been taken advantage of.

Dave

jmacd

Framer, I agree 100% and this has bothered me since we did the work. I am glad that I am on the same page as the rest of you guys. My reason for the post was to make sure that I wasn't missing something. This a tough racket.

$275 isn't enough to loose sleep over but sometimes just knowing you were taken advantaged of stings more than the money.

I have owned three completely different business's in my life.

I owned a retail store for 18 years, sold it, a building material brokerage 20 years( manufacturer's represented firm), sold it, and this excavating company and the excavating is the most challenging by far. Not so much the work we do but the people we have to do the work for. You have to really protect yourself in the construction biz more so than anything I have been involved in.

I enjoy the work a lot and it is still fun to go work on Monday, I hope that doesn't change as it did with the others over time.

bwalley

Add some wording in your contract that you are not responsible for final grade and that you will not accept backcharges due to final grade.