"jran" wrote in message
news:Ua1hc.20901$hw5.34484@attbi_s53...
while your at it put down some insulation around the outside edges


Not just the outside edges. Code calls for an R10 under the slab when you
heat hydronically in slab. It may cost a little to install the insulation,
but it will pay for itself in short order, especially with energy prices
headed higher and higher. If you plan to run a fork lift in the shop, or
install some very heavy machinery, the insulation comes in grades, up to 100
PSI. The typical stuff you see at the lumber yard is usually either 15 or
25 PSI. I used 40 for my shop, which appears to be more than adequate. I
have a fork lift that weighs just under 10,000 lbs, and it can pick three
tons. I've hauled one piece inside that taxed the capacity and got no
cracking or settling. I did do one thing to help prevent edge cracking,
though. I have rebar on 6" centers in the door ways, in a couple feet or
so, where you might get edge cracking. A few bucks spent before the crete
is poured can save a lot of heartache later.

Harold