The clear span of a structure is the distance between the inside faces of the supports. The seal span is the distance between the outside faces of the supports, including the seals.

In other words, the seal span is always greater than or equal to the clear span, depending on the thickness of the seals.

Seals are used to prevent water, air, or other fluids from leakingthrough the joints between the supports and the structure. They are also used to provide a thermal barrier between the supports and the structure.

The thickness of the seals will vary depending on the type of structure and the environment in which it is located. For example, seals on a bridge will be thicker than seals on a building, as they need to withstand more extreme weather conditions.

Here is an example of the difference between a seal span and a clear span:

Suppose you are building a bridge with a clear span of 100 meters. The supports for the bridge are 1 meter thick. To prevent water from leaking through the joints between the supports and the bridge, you install seals that are 0.5 meters thick.

The seal span of the bridge will be 102 meters, because it includes the thickness of the seals.

Seal spans are important to consider when designing and building structures, as they can affect the overall strength and stability of the structure.

Here are some other examples of where seal spans are used:

• Buildings with curtain walls
• Doors and windows
• HVAC systems
• Electrical conduits
• Plumbing pipes

I hope this explanation is helpful.