It is important that five specific objectives are achieved for all window and door flashing design and installations to ensure the opening around the fenestration is protected from water and moisture. The flashing assembly should systematically function to drain and dry.

These five basic objectives are fundamental to all flashing designs and installations. If one of the objectives are not met, the system may break down and result in failure – defined as unwanted water or moisture intrusion through the fenestration opening.  Each one of these necessary objectives is an application that provides needed protection, drainage and drying.


Objective1: Protect the rough opening.

This objective is focused on the rough opening for the window or door itself. It’s designed to make sure that we’re protecting the materials that frame up that rough opening.

Objective 2: Drainage at the sill.

The objective here is to divert any kind of water that might enter into the sill area either to a drainage surface behind the cladding or to the exterior cladded side of the wall system.

Objective 3: Drain at the head.

The idea here is to provide a pathway for any water that is draining between the cladding and the structural wall so that it drains from the head of that opening to the exterior side.

Objective 4: Seal the interior perimeter.

Sealing the interior perimeter gap between the window or door frame and the rough opening addresses concerns with air moisture and water intrusion or extrusion. Plus, in some cases, depending on the material used, it could also provide a bit of a thermal performance.

Objective 5: Seal the exterior perimeter.

This seal is necessary to prevent entry of air, water, and moisture into that space between the window and the rough opening.

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