Understanding Typical Window Sill Elevations in Residential Construction
In building construction, window sills play a key role in preventing water from entering a home when window components shift and settle over time. Properly built sills help protect the structural materials of a house. Most contractors follow a commonly accepted standard height for installing windows and their sills, though alternative design factors can lead to adjustments.
By Rowan Scott
The window sill helps to keep moisture out of home interiors.
Within building construction, window sills fulfill a significant role: they help block water from getting inside a home when window fittings move and settle. When sills are constructed effectively, they contribute to preserving the structural materials of the house. Unless other design considerations enter the picture, windows and window sills are typically installed at a standard height that most contractors accept.
Materials Used for Window Sills
In the past, window sills were commonly built from wood, stone, granite, brick, or other materials available locally that made construction convenient and inexpensive. The materials chosen for window sills generally matched the construction of the rest of the structure. Across residences in the United States, wood is the most frequently used material. However, wood sills are susceptible to water intrusion and condensation coming from windows. Rot can develop and advance to a point where the whole sill needs to be replaced. This drawback led to broader use of other materials. Marble and granite window sills are often seen in home construction today. Compared with wood, these materials hold up better against the elements, and they offer a high-quality sill surface that is both attractive and long-lasting.
How Window Sills Are Constructed
Windows can be built at any height, and because of their nature, window sills must follow the proportions of the windows. In rooms with high ceilings, windows placed at standard height would leave an excessive amount of wall area above them, which would be out of proportion with the rest of the room. To maintain the visual scale of the room, it becomes necessary to adjust the height of the windows and their sills to match these taller home designs.
Typical Window Sill Height
Generally, windows are built 3 feet above the floor. They are installed at the bottom of the windows. Sills are frequently attached to 2- by 4-inch blocks placed between the drywall and the wall studs, so that there is ample mounting material to support the sills. The sills are drilled and set into position, after which all seams are caulked to make them waterproof. When sills are going to be painted, the nail heads are filled with putty and left to dry before priming and applying a topcoat of paint.
Heights That Fall Outside the Standard
Windows and sills may be placed differently to accommodate ceiling height as well as other design factors, including natural light, unusual window shapes, and built-in structures near the windows. Windows that face east and west receive sunlight at a low angle during spring and fall, which can be blinding to the building's occupants. According to writer and general contractor Duo Dickinson of the ThisOldHouse website, raising the sill height to 4 feet off the floor helps reduce this glare.
