We are restoring a 100 yr old historical house. Will have many more questions to come. 1.We are going to replace about half of the wood siding on the exterior. The siding is nailed to the 2x4's on the exterior and there was plaster walls on the interior with nothing in-between. There is no room for sheathing on the exterior. We want to insulate the area between the exterior siding and the greenboard/plaster (not yet installed) walls. A) is there a product we can use on the interior side of the siding to seal the seams and provide with some fire protection? b)should we use a vapor barrier between the siding and insulation (as well as the insulation and greenboard)? c) Or will the siding alone be ok next to the insulation (rolled pink stuff)? I can find a lot of info on new construction, but I am limited in options in restoring this to its original look. Advice would be nice. Thanks for any assistance you can offer. 2. Same house - different question: The house has 1" pine flooring attached to the joist (no subflooring). In one area, the floor had been cut away to make room for a 'bathroom'. We've removed all this and want to install some terra cotta tiles since this area will be an exit to an upstairs sun porch. When we install the tiles (after installing 3/4" plywood and then greenboard), this will cause a difference in the floor heights of about 1", is this allowed? Or do all floor heights have to be the same? If the floor heights have to be the same, what do I do?