I am converting an existing garage into a workshop. I would like to float a wood floor over the existing concrete slab, so my first question is about sealing the existing concrete floor. Can anyone recommend a product for sealing / vapor protection from outside? The new floor will also be raised 6 or so inches. Should I get the voids under the floor foamed?
Second, I am going to remove the existing garage doors and install french doors. I would like to raise the level of the interior floor. For the french doors, I would like to raise the level of the foundation...in a sense, build a 6" high concrete foundation on top of the existing slab and then build the doors in on top of that. Should I use concrete block, or mix my own concrete?
A suggestion I have is to frame a floor with 2"X6" treated lumber 16" OC. Then sheet the new floor with 3/4" CDX. I would place a plastic vapor barrier over the concrete first then set you floor joist over the plastic. I think this would be less expensive than pouring a concrete slab over the existing floor.
Once you place the 6" floor will you have enough height for you french doors? If not you could frame the floor with treated 2"X4" floor joist. There is no worry about support for the 2"X4" because they will be in contact with the old concrete slab. Make sure you leave venting so that the area underneath the floor can breath.
Thanks, I'm definitely going to frame a conventional floor structure. I'd like to insulate it, but I'm not sure what to do about vapor protection and insulation material. What about foam in the voids between joists? Would that be too tight and not allow enough ventilation? Poly film and then fiberglass? Where does the moisture go if I put down a poly vapor barrier...around the edges and up through the floor cracks?