40x60 project - few questions

[scottyag02]

just found the forum today....great group here.

My project; 40 x 60 x 15 metal building, has been in the planning stages for awhile, and im finally getting things in gear. Had to cut down several trees, and just moved a shed (will post some pictures if I ever find my camera cable, it was like making a chevy truck commercial!). Just dug out the stumps with a backhoe, and was quite surprised by the craters left behind, maybe 10' diameter, & 4-5 feet deep

For the dirt work I plan scraping the area down about 6", and bringing in "select fill" to build a pad up about 2 feet, and compacting with a roller in 3 or 4 lifts. So a couple questions here;

1. For the "craters", I am trying to remove all the organic material from the cut dirt. Any suggestions on the best way to refill/pack the holes so im not left with sinkholes under my foundation? I dont see a good way to compact these areas. maybe a small plate compactor or one of those "jumping jacks" I did read a thread on this were "time" was mentioned as the best compaction method......however I don't want to slow down now!
2. I have seen alot of talk about using gravel below the slab. I had no intentions of doing so, nor have any of the contractors I have been dealing with mentioned it. What are the thoughts here? If it is deemed necessary should it be placed above or below the fill?
3. Just got a first quote on the slab, and was shocked. Any general advice on a DIY slab job?

Thanks, Scott

 

[Wardster]

1. Compact sand in 6" lifts with a plate compactor. Those jumping jacks are a pain to use.

2. Aggregate is typically used when the subgrade is an impervious material such as clay. By using aggregate, any water that may find its way beneath the slab is able to drain away instead of being trapped. If you are in Texas, then you probably have sandy soil that would not trap water.

3. You can save money forming it up on your own, but you should probably leave the placing/finishing to guys who do it everyday. I paid a contractor $1/sf to do my slab, but that number could move one way or another depnding on the size of the job.

-Wardster

 

[ron in sc]

I have seen alot of talk about using gravel below the slab

.

I've read about people using gravel too. About all I can say is I hired a geotek firm to do testing and make recommendations for the contractor to follow and no gravel was recommended for use under the slab/footer/stem wall.

We used plate compactor as Wardster recommended. We compacted 4" to 6" lifts.

 

[scottyag02]

Thanks for the replies.

-Scott