"Edwin Pawlowski" writes:

"Dan Espen" wrote in message

This particular patio consisted of a bunch of 4x8 concrete sections
separated by redwood 2x4s. It looked like they anchored the
2x4x in place by driving nails thru them and embedding the
nail into the concrete.

After living in the house about 10 years I had to replace the
redwood. It does eventually rot. I used pressure treated instead.

I've seen thing like that. In most cases, they do not have a lot of
reinforcement or are very thick. More like oversized patio blocks. May be
a OK in mild climates, but now where you'd have frost heaves.

Since I broke it up, I know what was there.

No steel. About 4 inches of concrete. Pretty much put
directly on central NJ clay soil. Just a bit of gravel
in some places.

There were definitely chipmunks living under the slab,
but not any obvious signs of dirt being washed out or
excessive tunneling.

I do think that despite the way the nails tied the
redwood to the cement, each slab pretty much moved
on its own. When the ground expands, that stuff
just has to move.