Concrete Slab Prep How Accurate

Originally Posted by 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.