Intrim offers custom size jambs to save time on site, reducing the need to.

Door jamb thickness. Door jambs must cover the entire thickness of the wall where the door will be placed. Top jamb length = door width + 3/16 inch + ½. Measure from the door frame to where the drywall starts, this is your casing, the measurement of the size trim you will put around the door.

If your rough opening measures 82 1/2 inches tall, cut the side jambs to length at about 81 inches, depending on how much clearance you want below the door. A standard door installed to the exterior makes for simple trim details, but it requires interior extension jambs, which means the door can only open a bit more than 90°. The exterior jamb reveal on a masonry wall is normally finished in masonry.

The door jamb is the frame that installs in the wall and supports the door via hinges. Door jambs are the vertical and horizontal timbers attached to the frame onto which a door is hung and secured. The nominal door height is listed as 6/8 which is 6 feet 8 inches or just 80 inches.

Focus on these two equations, 2 side jamb length = door height + jamb stock thickness + ¾ inches + ½ inches + 3/32 inches. The door jamb is the frame that installs in the wall and supports the door via hinges. Wall thickness includes the wall stud plus the sheetrock thickness.

In an interior door its 5 1/2 +sheet rock 1in. You need to figure out if sheer ply plus finished material plus interior sheet rock.