How to Install a Knockdown Metal Door Jamb

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Things You'll Need

  • Knockdown frame

  • Allen wrench

  • Tape measure

  • Level

  • Wooden shims

Hollow metal frames are primarily used in commercial buildings. They are available in both welded and knockdown versions to meet the needs of various applications. A knockdown frame comes in three separate parts, including two jambs and a short header sections. These frames are designed for installation in drywall partitions, and must be installed once the drywall work is complete. Knockdown units are very simple to install, and require only basic tools.


Step 1

Frame the wall correctly. A knockdown frame should be about one inch smaller than the wall opening in both height and width.

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Step 2

Choose the right size frame for the job. Measure the wall thickness around the door opening. A knockdown frame should have a throat size equal to the wall thickness. The overall jamb depth of the frame will be one inch wider than the wall. For instance, a frame that will be installed in a 4 7/8-inch wall should have a throat size of 4 7/8 inche and a jamb depth of 5 7/8 inches.


Step 3

Use the Allen wrench to retract the compression anchors in either side of the frame. This will pull the anchors toward the center of the frame and keep them out of the way as you install the frame.

Step 4

Angle one of the jambs so that you can fit it into the opening. Wrap the top of the jamb around the top of the wall opening. Press the entire length of the jamb down the length of the wall until it is firmly in place.


Step 5

Add the header. Most knockdown frames have clips or tabs at each corner that allow installers to connect the jambs to the header. Connect these clips first, then press the header up so that it wraps around the drywall at the top of the opening.

Step 6

Angle the second jamb so that it fits in the opening. Connect the tabs where the jamb meets the header, then press the top of the jamb into the drywall so it wraps around the edge of the opening. Press against the jamb to fit it around the wall, working your way down the length of the jamb to the floor.


Step 7

Tighten the compression anchors so that the frame is fastened securely in place. Use the Allen wrench to tighten the anchors so that the jambs stay tight to the drywall, but do not overtighten. Overtightening these anchors can dent or damage the drywall.

Step 8

Check that the head of the frame is level, and add shims under the jambs to even out the frame as needed. You may also need to adjust the compression anchors to complete this step.


Step 9

Install a spreader bar at the base of the frame to keep the unit plumb as construction proceeds. Most frames come with these bars, but if yours doesn't, you can construct your own from scrap lumber to help the frame hold its shape.


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