Concrete patio rebar design question

[gzecc]

Rebuilding the patio off the house. Found concrete block during demo which extends 4' deep. Should I rebar every few feet and tie into the wire mesh or should they not be tied together? Pouring 4" slab and will form up the front and sides.

 

[semipro]

It seems to me you have two options: tie in the new slab with the existing structure as best you can or isolate the two entirely.
I'd suggest filling in all sub-slab voids, including the block, with (plate) compacted sand, leveling it off and building a "floating" slab on top the old.
I think that tying into the blocks whether with new concrete only, or with rebar may create stresses in the new slab that may result in cracks later.

Edit: I'd also suggest having an air entraining agent added to the concrete if the slab is exposed to weather or salt.

 

[gzecc]

My thoughts exactly. Not sure if I should isolate the slab from the curb or tie together.

 

[Isaac Carlson]

If the area you are working on heaves at all in the winter you will have cracks. I like thicker slabs, like 6". I like 6 inches of gravel under them and bigger rebar if it gets used. You can put relief cuts in the slab every 6 feet or so to control cracking.