I'm trying to install some new base cabinets in our kitchen. We have removed the old ones and discovered that the kitchen floor slopes towards the center of the room, which means that these new cabinets will be sloped too. How should I deal with this? If we prop up the cabinet, then the cabinets will not be resting on the floor and you'll see a gap. If I install them on the floor, then the counterops will not be level. Any ideas?
If the floor in your kitchen is sloped, then you will have to level the kitchen cabinets before you can securely attach them to the wall. All sorts of problems arise when a cabinet is not level, from drawers and doors that won't open and close correctly to counter-tops that show unsightly gaps where they meet an adjacent wall. Remember, not only do your cabinets need to be level, but they must be plumb as well.
If you are installing your new cabinets against a wall, then use a level to first check the wall to make sure that it is plumb. If it is, then position the cabinets in place snug against the wall. If not, then you will have to shim either the front or the back of the cabinet box, depending on the "tilt" of the wall. Next you should level the cabinet by installing some wood shims under the low end. Make sure that the wood shims are positioned under the cabinet enough so that they don't protrude beyond any cabinet face. (The gap and the shims will eventually be hidden by a piece of trim.)
Once you have the cabinet level and plumb, then you can attach it to the wall with some cabinet screws. You should drill pilot holes to avoid splitting the wood, making sure that the screw is going through the top rail of the cabinet box and securely into a wall stud or other framing member. After all your cabinets are level, plumb, and secure, then you can install a piece of matching trim along the base of the cabinet to hide the gap and the shims.