I went by Lowes today as that is where he said he gets the product. The sales person there didn't know what I was talking about. I don't know if that is because they don't know the products they sell or if that isn't a normal combination. Then I went to a mega floor store and talked to them about it. They did have engineered installed on a membrane in their store, but said the reason is because they have to take up their floors and install the new stuff all the time and it's much easier than gluing down the wood to the concrete. The guy there said they never install their engineered wood over membrane, but could see how someone would if their foundation moved a lot. Another guy in the store said he has personally installed hundreds of floors on concrete and never used membrane. They both thought the GC was recommending this to pad the bill. I have no idea. I emailed the GC back and asked if he was talking about engineered or laminate. Our calcium chloride test came in today too. Maybe we can get that started tomorrow. Edited to add: The GC emailed back and said he uses both laminate and engineered over the membrane and none is glued down. It may be fine, but I don't have a good feeling about it since no one else seems to know anything about it. Is it a big deal to follow the manufacturer installation instructions or should I just let them do it the way they want? This post was edited by marti8a on Thu, Aug 22, 13 at 17:51

Congratulations on your project. You asked specificially about ceiling treatment, but there are also a host of other issues to convert an "exterior" space to a habitable one. Here's some thoughts about garage conversions: Floor slab: Is it solid with no cracks? Is it at house finish floor level or are you OK with a step down? Is it insulated below the slab and on stem walls? Are you in a climatic zone where winter coldness is a factor for the concrete slab? If so, floating a floor on sleepers (with insulation) above the top of the slab is an option. Walls: Will additional sealing of cracks and insulation be needed? Will new gyp board and trim be needed in some areas? Ceiling and roof: What sort of roof structure do you have? How will you insulate and vent the roof to prevent heat loss and moisture condensation/mold? You will likely be better served to have some sort of seperation between the habitable space below and the insulation/moisture barrier above which is usually not very visually attractive (what a ceiling usually does). Although I hate the look of a suspended ceiling, it may offer one inexpensive option for a new ceiling if the existing roof joists or trusses have uneven bottoms. Systems: How will you heat and cool the new space? Will you need to run new HVAC ducts, control wiring etc.? Will you need new electrical circuits, controls and a secondary panel? Need water and drainage? I'm sure you have thought through all of this, so pardon me if this is redundant. Good luck!

Sorry but you will have to rip up the floor. Garage floors are NOT dealt with in the same way as house slabs are dealt with. And if you add in the age of the garage (assuming it is the same age as the house) then you are in for a double dose of moisture issues. Garage slabs are often thinner and they NEVER have a moisture barrier incorporated under them (why spend money on a car house?). And garages are expensive to upgrade because they never meet code for indoor living space. These two things put together often mean a garage conversion will have been done 'on the cheap'....especially if this was done a long time ago. If this looks like it was a DIY conversion, I would assume the space is not up to code. It's the easiest assumption to make. Now for the smell. If it smells mouldy then it is mouldy. I'm going to guess that the flooring has to come up. Then the drywall has to be examined for any moisture damage. You will need to investigate whether or not the wood studs are SITTING on the concrete (NOT GOOD!) or if they are properly supported with metal brackets (better). On your hands and knees, go ahead and poke at the drywall at floor level (below the level of the flooring if you can). Use a metal screwdriver. If it pokes through like it is paper mache...then you have a rebuild on your hands. If the bottom of the drywall is still solid...you are in a better position. You are NOT guaranteed to be mold-free (on the walls) but you are in a better position than if there is ruined drywall. Whew! But first things first....get the flooring UP and inspect what is there. And make sure you inspect the drywall and the wood studs while you have a clear view. Send us photos of what you are seeing. We will help from there.

Assuming the garage is finished, but not finished to the same quality as the house, removing the drywall, insulating and putting up new drywall may not be cost prohibitive. You could use closed cell foam or other higher performance insulation to get quite a high R value in the walls. I would also remove the garage door and frame this like a standard wall so that it would be fully insulated. The floor is cold because its constructed of about 4-6" of cement on top of dirt. There may be no insulation under the slab. However, since you have ceiling height you could add 6" of foam insulation on top of the cement and then enclose that with new framing for a standard floor. Also make sure you have a good moisture barrier on top of the cement. Another possibility to warm up the room is to extend your existing HVAC and add a supplemental electric heat grid under the floor (usually works best with tile) so that it never feels cold. Most in-floor electric heat runs at a relatively low temp (maybe up to a max of about 84 degrees), so it never feels truly hot on your feet. I don't really like garage conversions because they almost always look just like a converted garage. However, if you need the space it might be a good choice for you. Bruce