"Ecnerwal" wrote in message
...
"PJ" wrote:

Put lots of rebar in the floor. I used the fiber, and don't think it did
anything except lighten my wallet. It certainly didn't stop
cracking...Paul

Neither will rebar, if you don't also cut some control joints (unless
very small, any slab will crack - you simply want to tell it where it's
OK with you that it should crack). I have both rebar and fiber in my
slab, and there are cracks running out from the ends of the control
joints (where the saw couldn't cut right up to the wall). No cracks on
the face of the slab (so far anyway), so I assume that the contol joints
have done what they are supposed to do.

--
Cats, Coffee, Chocolate...vices to live by

The beauty of rebar is even if you get cracking (and you will), it prevents
the slab from shifting. My shop floor is a full 6-1/4" thick, 6 sack mix,
with rebar on 12" centers two ways. Instead of cutting the floor, the guy
that finished it used a bull float and scored lines approximately 12' apart,
then finished over the score lines. That provides a weaker zone for the
crete to crack where you want it to. It works, and you don't get a big
line that fills up with crud like you get from saw cutting. I have
cracking, but only where he had scored and finished, so it's very narrow,
and there has been absolutely NO shifting of the crete. The floor is now 5
years old. I highly recommend rebar, although it does take a lot of time
and money to install it. If you do it yourself, it's not all that bad.
In my opinion, it's worth it. Cheap insurance when you consider the cost of
the job overall. I fully agree with a properly prepared base, too. Ours
was compacted well as the fill was installed, then it sat through a full
season of winter rain in Western Washington. We used rock for fill, 3/8"-
with fines. Worked out great.

Harold