Sod remnants under a garage floor?

[ScaldedDog]

I'll soon have the floor poured in our new 32x34 garage, but I noticed tonight that there is still some sod lying just below the surface of the dirt floor that's there now. I'm thinking that should be removed before the gravel is brought in, right? Wouldn't the grass eventually decompose, causing voids beneath the slab, which would then crack unnecessarily?

Sorry for the dumb question, if it is...

Mark

 

[g935cab]

Definetly get it out ,should be easy , i just got my permits and i took out 6 60 foot trees and have a bunch of roots to deal with and i want to have as few cracks as possible

 

[boiler7904]

Everything you said about leaving sod under a slab is correct.

You don't want topsoil or other organic material under the slab either as it doesn't compact as well as clay material. It will move and cause the same types of problems.

I've been involved with a building built on a site covered with fill - 1' of topsoil was buried under 12' of clay. Once the building went up, it started to sink. The back half of the building sank about 3 inches over the coarse of a couple of months. Believe me, this is not something you want to deal with.

 

[Kevin54]

Sorry for the dumb question, if it is...

Definately not a dumb question at all. And there are probably contractors out there that left sod under slabs and then the owners wonder why their slab cracked a few years down the road. Get the sod out and have the contractor use a plate compactor to tamp all the stone down before pouring the concrete.