What type of lath?
Casey

Metal diamond lath over all. Where we have new ceiling framing every 24" with additional blocking in between so wood support every 12" and then sound board before lath

Why is this important ? (I am not being sarcastic). I think I would trust your contractor, he is not using drywall which is cheaper and not the same quality as plaster.
Casey,
In this neck of the woods blue board is generally used. My 50 yr old house has rock lath 2 x 4 x 1/2 sheets of gypsum and plastered , very good product but not used any more. Wood lathes with a coarse scratch and finish coat hasn't been used in years.

More curious than anything. Our GC is great - I find myself remarking at least once a week how glad I am we found him
It was still a challenge to find a sub that would do the plaster - they mostly do stucco and had wanted to use Portland with sand for base coat but we weren't comfortable with that and GC had them use the gold
Bond product. GC did his own plaster at his housebut his labor rates are a bit high ;)

Plastering is a specialized trade, at least in Boston. It is not like taping dry wall or stucco. I am guessing you are out West because they wanted to use cement for a "scratch coat" or base. No one does that any more and most the pros around here are 1st, 2nd or 3rd gen old country.

Over expanded metal lath, typical to use structolite/gypsolite. You could use old-style lime mortar as well (horsehair plaster) but this is heavier and has a very long cure time.
Casey

Thanks! Yes we are in Colorado :). Hard to find folks that are willing to do plaster and have experience. They did the scratch coat yesterday and are doing brown coat now. So far think it is looking pretty good. Can post pics if people are interested to see. So glad we went authentic and took the time to find someone to do the plaster!

If you have some in-progress pictures and it's not too much trouble for you to post them, I'd be very interested in a glimpse of the process!

"You could use old-style lime mortar as well (horsehair plaster) but this is heavier and has a very long cure time. "

Lime-plaster cures reasonably quickly.

Lime plaster takes months to cure.

higher lime-plaster was normally restricted to the finish coat (the longer setting time allowed plenty of working time (troweling)for a smooth hard finish) with the base coats having other 'stretchers' (sand) or strength (fiber) additions along with retarder to slow setting.
Lime putty makes a decent retarder if other types are not available though.

This post was edited by brickeyee on Sun, Dec 30, 12 at 11:28

You oughtn't paint lime plaster walls for three months. That's the main reason for not using it; mist homeowners don't want such a long wait to finish the room.
Casey

Not sure how to do these inline w/o photobucket - but this is pre-lath

Paper and metal diamond lath

Scratch Coat

Brown coat

Katy-lou: thank you so much for posting the pictures!

Well it took them two attempts to get the finish coat correct
- apparently 16 grit sand is hard to find here and they had too much texture in the plaster behind the aggregate on the first attempt. So they came
Back and did a second attempt - still doesn't
Match the rest of the house quite right but pretty good anyway. Oddly it looks like old plaster. Our GC kept remarking that if we had asked someone to get it to look like
It does they couldn't have done it.

Ack! Contractor cutting out openings and putting in new windows today cracked the new plaster! Ugh. We know the plasters can't patch worth a damn so guess we'll be patching the brand
New plaster this weekend. Bother!