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What is a Soffit?

Soffit fascia and siding on a home exterior.

What is a Soffit?

Soffit is an architectural term that can be used in three contexts.  The soffit can refer to:

  1.  the horizontal underside (interior or exterior) of a construction element.
  2. any structure used to fill the space between a ceiling and the top of wall-mounted cabinets.
  3. material that connects an outside wall to a roof’s edge underneath the eaves.

The English word soffit is derived from the French and Latin words soffite and suffigere, meaning “formed as a ceiling” and “to fix underneath”, respectively.

Because of their plain appearance, soffits don’t call much attention to themselves and therefore are often overlooked.  But as part of the cornice or eaves, soffits help protect homes from weather elements.  Older homes are less likely to have soffits, but these can still be added onto eaves that don’t have them.

Where is it used?

Soffit and board installation.

You can find everyday examples of soffits on structures large and small.  These supporting elements can be seen on the undersides of arches or architraves (beams) supported by poles or columns.   Other common sites for soffits include the undersides of staircases and chimneys.

Soffits fill the space above kitchen cabinets or in the corners where the ceiling and wall meet.  In kitchens, soffits also come in the form of drop-down boxes from which ventilation hoods are mounted under ceilings that are sloped or especially high.  In office buildings, soffits are located on the undersides of ceilings where tiles are affixed to the wall.

Step into a recording studio and you will find soffits on any walls where speakers are mounted.

On a building’s exterior, soffits can be observed as any exposed undersurfaces of overhanging sections of roof eaves.

Although there are many types of soffits, the term is most frequently used to describe the material that bridges the gap between the top of an exterior wall on a home to the outer edge of the roofline (also called the eaves).  The soffit is often nailed or screwed to rafters which, because of their position, are often called lookout rafters or, simply “lookouts.”

Depending on a building’s construction, soffits may extend anywhere from a few inches to a few feet.  The surface may be ventilated to prevent condensation, but this isn’t always the case.  Ventilated soffits usually come with a grill at the bottom called a soffit vent.  Ventilation prevents the formation of ice dams, which occur when warm attic air melts snow and ice on the roof, which then runs down into the eaves where it’s cooler, only to freeze again and potentially cause damage.  Proper ventilation improves air circulation, which not only prevents ice build-up in the winter but also directs excessive heat away from the home during the summer.

Yellow soffits as seen in the apartments esigned by David Walker and EPR Architects in London, UK.

Soffits are made from a variety of materials, such as wood and wood products, or metal.  But the most popular material used for this part of the eaves is vinyl.  Metal and vinyl soffits come in a wide array of colors to match the exterior of just about any home.  They’re also low-maintenance and come in preformed lengths for easy installation alongside other preformed components.  Soffits are manufactured either as solid panels, or perforated to allow for adequate ventilation.  The type of material used depends on how the eaves are constructed and the standards established by local building codes.

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