Pole barn rat wall and floor / two pours or one?

[vortech91]

I live in Michigan and a lot of counties have made it a requirement to have an 18 inch rat wall around the perimeter of a pole barn. I have gotten a couple of concrete quotes and one is saying to pour the rat wall then come back and pour the floor, separating the rat wall and floor using vapor barrier. another concrete guy says to do it in one pour. who is right and why? Thanks

 

[RPH]

Mine in the suburbs of Detroit was poured as one. They just let the plastic hang in the rat wall trench prior to the pour. Concrete is good to this day and was poured in 1989.

 

[ConCretin]

I don't see that one option would be functionally better than the other. You'd be more likely to get shrinkage cracks with the monolithic version due to restraint from the thickened edge but it's manageable. You could get some differential movement with the other option.

From a cost standpoint, the separate rat wall would require more forming, additional backfill after the inside forms are stripped and two placements. The monolithic version would require more concrete but I still think it would be less expensive.

I'm not sure there is a right or wrong answer here but my instinct would be to go with a monolithic version due to it's simplicity