When most of us think about installing cabinets, we picture ourselves shimming them at the floor so they’ll be level across their width and plumb across their faces. Another consideration comes into play in cases where more than one cabinet will be joined together without some other thing (such as a stove) to break up the front plane: we want to make sure the faces are in a straight line, not higgledy-piggledy following bumps or concavities in the wall behind them.
With base cabinets, there are two ways to level casework at the floor. The most common involves shimming up a separate platform on which the cases themselves will stand. The platform runs the full length of the cabinet series, providing a flat surface, and is typically recessed relative to the cabinets’ faces to hide any irregularity in the fit of the applied toe-kick, which goes on after the cabinets are set. You find the highest point of the floor in a given run of cabinets, set the platform down and shim it level and plumb. Then you set the cabinets on the platform, fasten them together to form a unit, shim as necessary at the wall and screw in place.
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On most of my jobs, we scribe the cabinets to the floor, a technique that “Kitchen Think” covers in detail. With this method, we locate the lowest point of the floor in a given run of cabinets; instead of shimming the cabinets up, we cut their bottom edges down until they sit level and plumb.
Whether you’re building up or cutting down, in all cases involving more than a single cabinet it helps to screw the units together before you attach them to the wall. That way you can treat multiple cases as one entity, shimming at the wall so that the faces will be flat and plumb.
On our most recent kitchen job, Mark and I had to switch our thinking by 90°. Usually, when he’s gutting a room to the joists and studs, Mark takes the time to get the walls and floors flat and level. Sometimes this means cutting long, tapered wedges to build those structural timbers up; sometimes it means having at them with a power-plane, to remove a twist or a bump. On this job he straightened most of the surfaces, but he didn’t bother with the exterior wall. You know where this is going.
Naturally, that wall turned out to be a problem. The lower section of the wall was pretty flat, so the base cabinets went in easily. It wasn’t until we were installing the upper cabinets – three large, heavy units – that we realized we were in for some fun.
Here’s how we installed the upper cabinets plumb on an out-of-plumb wall and flat across their faces despite that bump.
I made a 1/8″ x 3/4″ scribe strip to hide the gap caused by the shims at the left end of the run.
— Nancy Hiller, author of “Kitchen Think“
Source: lostartpress.com