Building a Kneewall on Existing Cabinets for a Bar Top

Advice on framing details for an add-on kneewall. February 11, 2010

Can anyone tell me how to build a knee wall attaching it to a standard base cabinet for a bar top at 42"? I know I have to use 2x4's and screw then on from the inside of the cabinet but I could use a little more info.

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor J:
We build our knee walls out of 2x4's 16" on center and screw them to the floor either with drywall screws (wood) or lag bolts (concrete). Obviously you'd have to screw through the back of the cabinet into the knee wall. We put 2x4 blocking along the inside of the knee wall at the proper height/location so we can attach corbels to support the countertop. This enables us to space them like we want without regard to stud location.

What will cover the knee wall - raised panel, plywood, drywall? When we're doing one with raised panels, I try to build as much of the knee wall as possible in the shop and leave the side adjacent to the cabinet open. We plant everything to the floor or adjacent wall, then skin the inside and set the cabinet. If it's going to get plywood, we work from the side away from the cabinet. We always build 3/4" thick end caps that have a 1/4" rabbet that we can slide the plywood down into once we have the knee wall the way we want it.

If it's getting drywall (and not angled), I usually tell the GC to let the framers worry about it. We like to build them if they'll be angled. The cabinets always fit better. If the knee wall needs an electrical outlet you need to know that before you put the knee wall together. That's a code issue in some areas. I've seen situations where the electricians didn't rough-in for the knee wall outlet. The knee wall got installed only to be torn back apart to make the electrical inspector happy.

From contributor S:
What is it that you need help with because you basically answered your own question. Is this for a freestanding island? If so, start by building your wall flat on the floor with 2x4 or 2x6 studs, a double top plate and a single bottom plate. Then add some solid blocking at the 36"AFF mark. Skin it with 1/2" plywood making sure that it is square before you nail it off. Stand the wall up and then use Tapcon , Hilti or screws to fasten it to the floor with the 1/2" plywood on the side opposite the cabinets. Set your cabinets against the exposed studs and fasten it with screws into the blocking.

From contributor M:

I assume you are trying to increase your height from 36 to 42 inches? Why use 2x4ís? Just rip up some 3/4 plywood and build a stud wall as you would with 2x4ís. It will be much lighter and straighter. Then you can attach it to the base cabinets, screw your top on and then attach a panel to the front or whatever you are using to finish it.

From contributor D:
I don't recommend a double top plate. If you've got backsplash outlets the single plate gives you (or the electrician) more room.

From contributor L:
Through-bore some 1" holes in the studs a couple inches down so it is ready for wires.