Exterior Window Headers & Surrounds

Header

• Inside the wall, at the top of the opening for the window, an installer puts in a header piece. Do not confuse this with a head casing, which is the top piece of the surround that is visible from the outside. A header is installed before the window, and it fills in the gap in the wall to frame the window from the inside. This makes the window more airtight. The mirror of the header under the base of the window is the sill.

Surround

• The surround, also called the casing, consists of trim installed on the exterior of the window at the top, bottom and sides. This frames the opening for the window, but it should not be confused with the window frame, which holds the glass in the window. The surround for one exterior window should match the trim on the other windows and doors on the outside of your home. Some windows have casing already installed on the window, but you can add more trim over this to match your home's design.

Materials

• Exposure to the elements will quickly wear away the finish of a window's surround. For painted surrounds, plan on repainting every four years. Consider adding a wood sealant over the surround pieces for longer-lasting protection. The wood used for the surround needs to be rated for exterior use, and the header requires a thick piece of wood to fit between the studs.

Drip Cap

• Once the header, window and surround are installed, you are not finished with your window. On top of the head casing, you should install a drip cap, which can consist of sloped wooden pieces extending 1 inch past the edge of the surround. Another type of drip cap uses metal flashing to create the sloped surface. Whichever type you choose, you will need to attach it to the top piece of the surround to protect the window parts from excessive moisture exposure.