Sunroom Terminology

The following is a summary of sunroom-related terms provided courtesy of the National Sunroom Association.


Click Here for the official publication provided by the NSA, reprinted here for informational purposes.


The terminology information encompasses many common terms used in the sunroom industry. You will note
that some terms are cross-referenced to a “primary” term. The “primary” term is the one that would be used
most often in sunroom publications.
Concerning the term and definitions contained in this Sunroom Data Sheet, please note the following:
• This Sunroom Data Sheet is not to be construed as a standard-type document, and therefore the
terms and definitions contained therein do not imply or suggest a given use to particular
• This Sunroom Data Sheet includes a compilation of commonly used terms, and may not be
considered complete from an industry viewpoint.
• The terms and definitions are not universal. Variations within the industry may exist with regard to
precise meaning.

2021, rev. 4/1/21 – NSA

Note: This document is reviewed periodically and may be updated. Visit for the latest version.

Awning Window: A hinged window that opens horizontally.
Batten: A two-piece assembly that facilitates the attachment of two roof components.
Casement Window: A hinged window that opens to the left or the right via a cranking mechanism.
Chase Way: An opening in an extrusion allowing wires to be run internal to the wall system.
Cricket: A roof structure that is designed to divert water around an obstacle or low point to ensure water is
properly evacuated, and is normally the same pitch as the rest of the roof.
Double Hung Window: An operable window with two sashes where both the top and bottom sash will
operate to allow for additional ventilation.
Electrical Box: Plastic or metal box that can be used to make electrical connections, house outlets, or
switches, and should be listed and CPSC compliant.
Engineered Lumber: See Laminated Verneer Lumber.
EPS: A type of foam plastic, known as expanded polystyrene, used for its insulative properties in sunrooms.
Fascia: A decorative component used to cover and seal the end of a roof panel, to reduce opportunity for water
infiltration and aesthetically change the look of the end of a roof system.
Flashing: Sheet of thin, impervious, exposed or embedded material used to prevent water penetration into a
building and to direct the flow of moisture in walls.
Footing: Concrete, block, or aggregate piles set below the frost line to support the foundation and prevent
heaving or settling of a structure; the sizing of these must be properly engineered to support the room and
support structure being built.
Frame: Exterior assembly that contains the window sashes and screens.
French Door: A swing door that has two panels, both of which open from the middle and can open either to
the inside or outside of the home.
Frost Line: The depth of frost penetration in solid ground, or the depth at which the earth will freeze and swell,
dependent on the geographic location.

Gable Roof: A room that peaks in the middle, as looking at the existing structure, that slopes down to the
outside walls on both sides.
Garden Patio Door: A swing door with two panels, only one of which opens, that can open from the outside
framing or center mullion and can swing inside or outside of the home.
Glazing: Rubber or silicone bedding that seals the glass to the window sash.
Glazing Bead: Removable component of a window sash that is snapped in to hold an insulated glazing unit in
Gutter: A type of side fascia that is designed to capture water running off of the roof, channel it to a specific
low point, and allow it to evacuate.
Header: Top horizontal structural component of a window, door, or wall section.
Hip Roof: A roof that has four inclined sides.
I-Beam: A structural roof mullion that facilitates the attachment of two roof components.
Jamb: Vertical window or door frame component that provides vertical structure to the unit.
J-Channel: Vinyl or aluminum component that is used to enclose the cut end of siding to provide a clean finish.
Joist: A horizontal structural member used in framing to span an open space, often between beams that
subsequently transfer loads to vertical members.
Keeper: Fixed component of a window lock that accepts the lock cam.
Knee Wall: A wall or window less than three feet in height used as a base wall in a sunroom application,
typically either glass picture windows or foam core panels with aluminum or vinyl skins.
Lag Screw: A mechanical fastener used to connect load bearing lumber or other materials.
Laminated Verneer Lumber (LVL): Lumber with specific engineered properties, used for the building of
sunrooms and decks.
Ledger Board: A horizontal lumber beam attached to an existing wall and used to tie in construction elements
such as porch roofs and decks.

Monoslope Roof: See Shed Roof
Mullion: Vertical or horizontal component used to join two units together such as window to window, window
to door, or unit to framing, within an opening or sunroom wall system.
Peak: The highest point of the room structure, which can be internal within the room or external where the top
of the roof will tie in to the home.
Picture Window: A non-operable window used in a replacement or sunroom application.
Pier: A vertical load bearing member of a deck or support structure for a room.
Pitch: Slope of a roof panel, typically in inches of vertical increase per 12 inches of horizontal travel.
Post: Vertical component used to carry loads on a structure.
Raceway: A cavity within an extrusion that is used to house electrical wires internal to a wall system. [Note:
Unless electrical connections are being made in this cavity, it is not typically required to be UL listed. If products
do not carry a UL listing, all electrical connections must be made within a labeled box to be compliant with codes.] Ridge Cap: External assembly attached to a roof to allow venting from within the space.
Rim Joist: A joist attached perpendicular to other joists, providing lateral support for the ends of
the joists while capping off the end of a floor or deck system.
Roof Panel: Multi-ply panel used to cover the top of the room and bear any environmental loads (either snow
or wind) associated with sealing the room.
Sash: Operable portions of horizontal sliding, vertical sliding, and hinged windows.
Shed Roof: Single slope roof that slopes away from the existing structure.
Side Lite: Unit placed next to a door to give the illusion of another door lite panel, used to maintain a door
aesthetic while utilizing a configuration in lieu of a larger door.
Sill: The bottom component of a window, door, or wall section, meant to tie directly to an opening or framing
and facilitate water evacuation from a system.
Sill Plate: Bottom horizontal member of a wall or building to which vertical supports are attached.

Single Hung Window: An operable window that has two sashes where only the bottom sash will operate.
Skylight: A fixed or operable window installed in the roof of a structure to allow for additional ventilation or
light entry into a space.
Slider Window: An operable window that has two or three sashes that slide horizontally for ventilation.
Sliding Glass Door: A two to four sash door with a combination of fixed and operating lites that slide to allow
for egress and ventilation.
Studio Roof: See Shed Roof
Swing Door: A single or dual panel door hinged on one side and designed to swing in or out.
Tie-In: Mechanical fastening and sealing of the room and roof to the existing structure.
Transom: Unit that is placed over top of a standard wall unit to allow for increase wall height.
Trapezoidal Panel: Angular window with 4 sides, typically used directly under the roof on the pitched wall
of the room.
Wing Panel: Trapezoidal panel located between the windows and the roof on the pitched side.
Wool Pile: Material commonly inserted in window sashes and frame to seal two moving components, placed
to reduce the amount of air or water infiltration through an opening while still allowing the components to

Last Update: August 25, 2022  

August 25, 2022  Engineering  
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