How to Build an Entrance Door Jamb

Depending on the size of the entrance door and the opening for it, the material used to build an entrance door jamb can differ in width. It can also differ in type, but this usually matches the wood type of the door. The thickness of the wall is a crucial measurement as it determines the width of the door jamb material.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• 2 pieces lumber, 1 by 6 by 96 inches
• 1 piece lumber, 1 by 6 by 48 inches
• Table saw
• Electric miter saw
• Router w/straight bit
• Carpenter's square
• Door stop material
• Variable speed drill
• 1/16-inch drill bit
• Phillips head screw tip
• Hammer
• 4d finish nails
• 3-inch drywall screws
• Nail set

Cutting

1. 
    
   Crucial Measurement

   Set the table saw fence at the width of the wall at the door opening. Be certain to include the inside wall material (such as sheetrock) and the outside material as well. Rip the three pieces of 1 by 6 to this width. If the wall thickness is greater than 5½ inches, you will need to use 1-by-8-inch material.

2. 
    
   Measure the Width

   Measure the width of the door opening at the top. Mark the 48-inch lumber and cut it to fit with the electric miter saw. The standard height of an entry door is 78-5/8 inches. This means the sides of the door jamb need to be 80 inches to allow for the threshold and the door sweeper.

3. 
    
   Steps 3 and 4

   Mark the two 96-inch pieces of lumber at 80 inches and cut them with the electric miter saw. Measure down from the top of the door to the top of the top hinge. Measure down from the top of the side on which the door will hinge, add 1/8-inch and make a mark. Place the corresponding hinge on the mark and trace around the shape of the hinge with a pencil.

4. Measure from the bottom of the top hinge to the top of the center hinge and mark the jamb accordingly. Place the corresponding hinge on the mark and trace around the shape as in Step 3. Next, measure from the bottom of the center hinge to the top of the bottom hinge and mark it as you did the other two.

5. Cut the hinge shapes out with a router. Be certain the depth of the cut matches the thickness of the hinge. Install the hinge plates inside the cutouts.

6. 
    
   Mark for the sides

   Mark the center of the top piece of the entrance door jamb. Measure the width of the door and add ¼ inch. Divide that number by two and measure from the center mark in both directions and make a mark. This is where the side pieces of the door jamb will secure to the top piece. Place the carpenter's square on the marks and draw lines across the width of the material.

7. Mark a piece of the door stop material the same as the measurement calculated in the previous Step. Cut the door stop so there are 45-degree angles on both ends.

Assembly and Installation

8. 
    
   Marking the door stop

   Measure the thickness of the door and add 1/8-inch. Mark the three entrance door jamb pieces from the inside edge of the jamb accordingly. This is where the door-stop material will be secured. Apply glue to the back of the door stop material for the top piece, place it on the line and secure it with the 2d finish nails. Drilling pilot holes with the 1/16-inch drill bit will make this process easier to accomplish.

9. Cut two pieces of the door stop material the length of the sides of the door jamb. Cut a 45-degree angle on one end of each so they will meet the angle of the top piece. Apply glue to the back of the pieces and secure them to the jamb as in Step 3.

10. 
     
    A Look for the Fit

    Secure the sides of the door jamb to the top of the door jamb with the 4d finish nails. Set the door jamb in the hole for the entrance door. Place door shims between the jamb and the studs where needed and secure the jamb to the entrance door opening. Secure the hinge side first. Place the carpenter's level against it to be certain it is plumb.

11. Place the level on the top piece to be certain it is level. Adjustments can be made by lifting the remaining side of the jamb. Secure the top and the remaining side with the 4d finish nails.

12. Install the door by slipping the hinge plates on the door with those on the jamb and tapping the hinge pin in place. Install the knob hardware and trim the door with door casing.

Tips & Warnings

• Clean up excess glue immediately with a damp cloth. For added strength, remove one of the hinge screws from each hinge on the jamb and replace it with a 3-inch drywall screw.
• Do not raise the blade of the table saw any higher than necessary to make the cut. Do not leave power tools unattended in the presence of children.

References

• L&W Exterior Door Unit Measurements
• Installing the Lockset, Door Casing and Trim

Resources

• Installing an Exterior Door