Preparing a base for under a slab - Correct procedure?

[tickridgescott]

Hi, first of all, thank you for this wonderful site. I highly commend the web developer.

My question is in prep work for slab. I am building a cabin with radiant floor heating, slab on grade. I have dug and installed french drains around perimeter of the 'to-be- cabin. Now I need to level the site and provide a sub base in one step. Area has already been stripped of topsoil down to a decent, moderately hard clay. south east corner of cabin site is 1 foot higher than northwest corner. I was planning on getting a basic crusher run or crushed gravel and installing in 4" increments and vibrate compacting it down. 3" or so on the high corner and 15 or so inches on the low corner and leveling the hole thing in this manner. Then i will be building atop this with a monolithic slab (on top of 2" foam board). I certainly down't want my radiant floor slab to move much so I am wondering if this sub base prep is correct.

ANother question here is that I am hoping to sort of slope the built up gravel out, meaning there is no retention on the side. This is because I have a french drain 12" out from edge of proposed slab. Do you think this would be adequate? I will also backfill halfway up the side of the slab.

Any comments would be appreciated.
Thanks!

[tickridgescott]

oh, one other thing...... would it be advisable to install geotextile fabric under the crusher run in order to insure against any possible settling in future? Thanks for your comments.....

[Tony McC]

Sorry, but Merkin slabs-on-grade are beyond me. Maybe one of our US-based cultural attacheés can help, but I can only advise on British and Irish construction techniques.