Skylight SealsSkylight seals from Elasto Proxy can meet requirements for dead loads, live loads, local maintenance loads, and wind compression loads.

Skylights are windows that are installed in a building’s roof or ceiling. They admit natural light, support passive solar heating, and provide a visual connection to the outdoor environment. Skylights feature large spans of glass, but there’s more to these windows than meets the eye. Glass loads can be heavy, and wind loads can add weight and pressure to skylight panels. If heavy loads cause a skylight to collapse, people can get hurt. Serious damage to a building’s interior can result, too.

Skylight Seal Requirements

To support glass loads and wind loads, skylights incorporate metal supports. Aluminum, a strong but lightweight metal, is typically used. These metal supports feature channels where rubber skylight seals lock into place. Window rubber provides sealing and insulation, but skylight seals also prevent the glass from contacting the metal. This especially important during skylight installation and maintenance, and during weather events such as windstorms and snowstorms.

For skylight designers, it’s also important to consider that the seal may support glass with potentially slight but significant variations in thickness. Glass, metal, and rubber have different expansion rates, too. Selecting the right skylight seal can be challenging, but help is available. Elasto Proxy, a custom fabricator of skylight seals and other industrial rubber products, can help your engineering department with seal design and compound selection. We also understand the load testing requirements you need to meet.

Types of Loads

Skylight seals need to withstand four types of loads.

Type Description
Dead Load (DL) The load from the materials of construction. This includes the skylight glass and metal supports. Most roof or ceiling systems have a fairly uniform density, which means that the weight of materials in one skylight section is the same as in another. Typically, dead loads don’t change much over time.
Local Maintenance Load (ML) The load on a specific part of a skylight, such as when a worker stands on a glass edge during construction. Local maintenance loads can be very high during installation, especially when workers stack glass or setup and use equipment.
Live Load (LL) The load from temporary objects such as snow, ice, planters, and decorations. Note that live load includes the total weight of workers, materials, and equipment during skylight installation and maintenance. Total weight is different than the local maintenance load, which is specific to a localized area.
Wind Compression Load (WC) The load created when wind’s dynamic energy is stopped by the skylight’s static surface. Wind loads exert pressure on the skylight glass, forcing it downward and towards the metal support. Wind compression loads vary, and skylight designers must account for regular wind gusts and high winds that occur infrequently.


Depending on the system of measurement, these four loads are expressed in kiloNewtons (kN) per meter (m), or in pounds (lb) per feet (feet). These expressions are written as kN/m and lb/ft, respectively.

Load Combinations and Safety Factors

In addition to individual loads, skylight designers need to consider a combination of loads. Depending on the skylight’s design and the application conditions, these combinations are typical:



Skylight designers may also need to consider safety factors, a measure of the load-carrying capacity beyond the expected or actual loads. Like roof and ceiling loads, safety factors are often specified in design codes or industry standards.

Get the Custom Skylight Seals Case Study

Do you need rubber seals for custom skylights? Elasto Proxy is ready to help. In addition to design assistance and help with compound selection, we provide custom fabrication you can count on. To learn more about how Elasto Proxy solves sealing challenges, download the Custom Skylight Seals Case Study.

Custom Skylight Seals Case Study