Tamped the floor in prep for concrete...

[hockey88fan]

I searched the site and didn't find what I was looking for so I'll ask the question I have and hope for an answer. I tamped the interior of my garage along the stem wall where we had back filled with the shale soil that was there. I'm using a Wacker jumping jack gas powered tamper, let me tell you that thing really has some power and is a bear to handle, my hats off to those guys who have to wrestle with that machine all day. Anyhow, along the stem wall it compacted the shale so tight that it drop the soil elevation a good 3 to 4" along the stem wall. My question is should I fill with more shale and tamp again or can I just fill the lower portion along the wall with the 2b clean stone I'm using for the base? In other words I am putting roughly 4" of this stone as a base for my pour but along the walls it would be about 7 to 8" of this stone. Thanks!!

 

[ConCretin]

If I understand correctly, you plan to install crushed stone (no fines) under your slab that will vary in depth from 4" to 8" due to an uneven sub grade. You're fine.

 

[gatchel]

The more stone the less compacted old soil the better. I have about 20 yds of stone under my floor spread and compacted every 6". No problems so far. I also am not a concrete guy so you may want to wait for other also to also chime in.

 

[ConCretin]

I'm not sure I buy it completely but engineers up here typically consider crushed stone to be 90-95% compacted when placed. I''ve built parking garage foundations on 15 ft of 'un-compacted' crushed stone. A few extra inches won't bother.

 

[jsmith6752]

Don't do what I did. After waiting about 2 years with a crushed stone floor I decided to go with radiant. I had one hell of a time digging my perimeter for insulation board. Just my 2 cents