I am finally adding a screened porch to the rancher here in Maryland,
and it may become a 3 season room someday. The porch will be 30"
above grade, so I'll have footers, 8" block, and fill. I'm having
this professionally done.

They will cap with 8" shoe block, fill with #7 stone, foam board
insulation (outer edge) and 6 mill poly plastic for vapor barrier.
Concrete will be 4" thick, 3500 psi, with fiber. They will use 1/2
inch rebar and wire reinforced.

The existing house (30 years old) foundation (block) only comes up
about 12" above grade. I plan to ask him to replace the t1-11 siding
on the house with 6" block where the new patio meets under the sliding
glass door. Make sense? If not possible, do I use OSB and flashing?

Some of the new porch will be up against the existing brick chimney.
Does this need to be tied together, or is an expansion joint better?

Lastly, we want to stain the concrete. We can have it pre-stained and
poured for one solid color, or a broadcast die added after the pour.
The other option (which SWMBO prefers) is the acid stain 28 days later
- from the internet pics these look to be the nicest floors. Any
experience here? I hard fiberglass may show up when doing the acid
stain, so we shold leave that out.

Ok -anyone with experience or expertise, let me hear it. I want to do
this the right way, one time.

Thanks!