Helpful Terms and Definitions

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Apron

Flat trim piece placed horizontally just beneath the window stool.

Brick Molding

Milled trim piece that covers the gap between the window frame and exterior finish
Casing

Cripple Studs

The short stud pieces that distribute weight over the header and help support the window under the subsill. When windows are located near the top plate or floor, upper cripple studs can be eliminated with a wider header.

Drip Cap

A horizontal moulding placed above windows to divert water so it drips beyond the frame.

Glazing

The process of securing a pane of glass into a frame using glazier’s points and glazing compound. Also referred as the layers of glass and their coatings.

Header

A horizontal framing member installed above a window to transfer the building’s load from above the opening to the supporting wall structure on either side of the opening. A properly sized header keeps the structure from sagging, or worse yet, collapsing at the window opening. Header size is based on the rough opening size, the bigger the window, the stronger the header must be. Factors like overhead floor length and joist spacing may be involved in calculating header size. Check with your local building inspector for requirements.

Jamb

The side and head trim of a window frame.

Millwork

Generally all building components of finished wood that are made in a woodworking plant or planing mill. Includes window sashs, door and window frames as well as trim moldings.

Mullion

A vertical or horizontal member that divides adjacent window units.

Muntin

A smaller, secondary member that divides the glass or openings in a sash or door. The look of a divided light is frequently created with a snap-in muntin grill.

Parting Strip

The small strips of wood placed in the side and head jambs of a double hung window to separate the upper and lower sash.

Rail

The horizontal members of a window sash.

Rough Opening

The framed-in, slightly larger opening that replaces wall studs to support the structure and accommodate a window.

Sash

The frame containing one or more panes of glass.

Sill

The framing member forming the lower side of an opening that supports the window’s weight. Cripple studs support the sill.

Stile

The vertical members of a window sash.

Stool

Horizontal trim piece attached to the sill. The bottom rail of the lower sashs in a double hung window rest against the stool.

Stop

Small molding strips attached to side and head jambs to guide and stop a moving sash.

Trim

Moulding applied around interior and exterior window to cover the gap between the frame.