Greetings, I have an 1870 2 story brick home, plaster and lath walls and looks like SYP for the flooring structure, and a small basement under the kitchen portion of the house. Since the plaster and lath is in good shape (8-12 inches thick), I am planning to use 1x3x10s as furring strips to attach the 5/8 drywall. Do I use a vapor barrier or will that cause mold? Can I use caulking to seal up any air gaps- there is styrofoam currently between the already applied furring strips. The flooring under the first floor just seems to be above grade, looks like a sealed crawl space- do I need to go under and place a vapor barrier on the ground and maybe replace all of the 1st floor wood? Any help would be greatly appreciated. I am wanting to deal with any sources of mold, so I want this done exactly correct. Thanks.

Well, this site was so very helpful.

Dana may find you, but you may also want to post your questions on the this website forum:

http://www.oldhouseweb.com/forums/

To figure out the mold potential and whether a vapor barrier hurts vs. helps we need more detail.

What is your location (for climate assessment purposes)?

How deep are the roof overhangs?

How is the original lath attached to the brick, and is there an air gap there?

What type of "styrofoam" did you hang between the furring? (Brand name & type, type of facers, if any.)

How is the furring attached to the brick?

How are the floor/ceiling joists supported?

In general polyethylene and foil vapor barriers cause more problems than they fix in most US climates, but that's not to say there aren't exceptions. It's possible that even the sheet foam already installed could be a problem, depending on the rest of it.