Basement Slab Question

[nightice]

Finally got our basement slab poured. Went to look at it today after it was dried (well, the rain pooled up on it.) Nonetheless, it has been ppured now for almost 3 days. I was walking on it and noticed that there are a couple places where slight "bulges" arise in the concrete and in a few places it is a little unlevel. Nothing too much..very minute, but I noticed it. My wife says that with flooring of some type (padding/carpet or whatever we use) it would not be noticeable. Is this pretty typical when puring slabs? The deminsions are around 50x30, thereabouts. Talked to my step-dad, who used to build houses, and he says it is nearly impossible to get a concrete slab perfectly level everytime. Arggggh!! :x

[Rich]

It is difficult.. but can be done when all the variables are perfect, and the planets align. j/k
We use a system called "SuperFlat" - started at the World of Concrete quite a number of years back. It's worked out very well for us.. on most jobs we'll have a FF requirement of 25 minimum and we consistently hit over 40 and sometimes 50.

[nightice]

Thanks, Rich. You must be on these boards as your other full-time job! :)
So, is this acceptable or tell my contractor to fix it and make it right? He is so far over $5k on budget. I'm sure he canmake it up somewhere before finishing the house. Framing should start this week. So from there, maybe he can make up for it somewhere. If the contract price was fixed at a certain amount and he goes over, does he eat it? I kow I sure ain't paying for the difference. Thanks Rich for the great site and wealth of info!!

[Rich]

He will have to eat it, as long as it's not a change initiated from you.
If it's a pretty noticeable hump in the slab (where it could cause you to trip) I would ask him to grind it down - it's not hard unless it's a huge area. I try and keep nothing more than 1/4" in 10'.. which for residential is pretty good (FF25).

[Timothy Hampton]

Rich is right, a FF# of 25 is generally acceptable for residential flat work (no more than 1/4'" high or low in 10') I've used a ten foot section of pipe and rolled it around on the slab and measured the variances. With some of the "dump and run" concrete contractors I know, if you get an FF# of 25 you're lucky! If the slab is to be covered with carpet or tile, grinding would be the solution for high spots and a floor leveler would help the low ones. If it's a finished floor say a garage slab, either live with it or have it replaced.

[Rich]

haha @ your signature Timothy. I always liken concrete to riding bulls - it's not if concrete's going to crack - it's when and how bad.