How to Install Post and Lintel Door Casing

A post and lintel door casing is similar to any other door casing, except that it follows the concept of a header or horizontal beam supported by two posts. Unlike, mitered door casings, installing a post and lintel door casing can be done directly on the door without pre-assembling the pieces on a flat surface.

Step 1 – Prepare the Door Casing Parts

A post and lintel door casing can be bought from a home improvement store. It can also be built as a DIY project, especially for doors that do not follow standard measurements or dimensions. The casing consists of two vertical pieces that will be installed to the right and left sides of the door, a horizontal beam called the lintel and two optional plinths or base moldings that serve as the base for the structure. Measure the height of the door jamb first as well as the width of the topmost portion. Cut the pieces according to the measurements taken.

Step 2 – Install the Plinths First

When installing this type of door casing, always start with the base first. Make sure that the base moldings or the plinths are installed flat against the wall and the door jamb to ensure that the vertical pieces will be installed correctly afterward. When the plinths are not installed properly, it reflects as the vertical pieces get installed.

Step 3 – Install the Vertical Pieces Next

Proceed with the installation of the posts or the vertical pieces of the door casing. Position one of the pieces on the door jamb first to check if it sits on the base molding perpendicularly. If not, adjust the base molding first to ensure that the vertical piece will be installed correctly. As soon as the vertical piece is perpendicular, clamp it against the wall and start nailing. Do the same with the other vertical piece. Make sure that the two pieces are perfectly vertical, and that the top of both pieces lines up perfectly and on the level. Adjust the pieces for a perfect fit.

Step 4 – Install the Lintel Last

Position the lintel on top of the two vertical pieces and make sure it rests perfectly on top. If the top of the 2 vertical pieces doesn't line up on the level, it will become apparent as soon as the lintel is placed into position. Clamp the piece and start nailing.

Step 5 - Apply Caulk and Wood Putty

Apply caulk on the seams of the pieces and apply wood putty in the holes where the nails were shot. Allow the caulk and the putty to dry before sanding the door casing to prepare it for painting or staining.

Step 6 – Apply Paint or Stain

It is important that the pieces of the post and lintel door casing are sanded properly before applying paint or stain. Use paint that matches the color of the door or the wall. Apply stain as an alternative if preferred.