I'm adding a room to my garage which runs along the back wallIt has fire-resistant smoke-sealed doors on both sidesI'll be using it for painting and I want a good seal to keep the fumes out of the main garageI've installed the door, but the sill plate is 3/4quot; higher on one side due to the slope of the garage doorWhat can I use underneath this to brace it so that it doesn't flex when stepped on? The floor has an epoxy finish so I don't think cement would workWould expanding foam work, or would it break down after awhile? Is there a caulk that can be used under the edges that would eliminate the flex?Thanks
Best bet is to sand off the epoxy coating under where the sill will go and get yourself some non-shrink grout and concrete bonding adhesiveFollow the instructions on the packagesIt is self explanatoryFor something that thick, you probably will have to make a form to hold back the grout from spilling outThe grout is usually rated for up to 3/4 thickThe foam and the caulk will not hold up to someone walking on the sillGood luck!
