DON’T GET “JAMB” UP: KNOW YOUR WALL THICKNESS
Nov 13, 18
What determines the jamb depth?
Part 1: Jamb depth starts with determining the wall thickness. So, how do I know what the thickness of the wall is? The partition types indicate the wall thickness. The partition types include the width of the stud, the thickness of the drywall (both sides), and the thickness of finishing material on each side (i.e., tile, paneling, etc.). Adding the thickness of all of this material together equals the WALL THICKNESS. Wall thickness is also known as the throat.
Part 2: After determining the wall thickness you need to account for the “backbend” of the frame. What’s backbend you say? That’s the part of the frame that extends beyond the wall thickness to complete the frame. Hollow metal frames typically have a backbend of ½” on each side. The wall thickness PLUS the backbend gives you the JAMB DEPTH.
EXAMPLE: For example, 3 ⅝” metal stud plus ⅝” sheetrock (each side, which is 1 ¼” total) equals a 4 ⅞” wall thickness. When you add the additional inch for the backbend, your jamb depth in this case is 5 ⅞”. Voila!