pan flashing
Pan flashing for exterior doors is a crucial component used in building construction to prevent water from entering the structure around door openings. It acts as a barrier that catches and directs water away from the building, helping to protect the integrity of the building's envelope and prevent moisture-related damage such as rot, mold, and structural weakening.
How Pan Flashing Works
Pan flashing is installed at the base of door frames, particularly for exterior doors. It consists of a sheet of material that forms a shallow "pan" beneath the door threshold and the surrounding areas of the door frame. The main functions of pan flashing are:
Water Collection: It collects any water that may penetrate through or around the door, especially water that can seep down the face of the door or through the spaces between the door frame and the building structure.
Water Diversion: After collecting the water, pan flashing directs it outward and away from the building, usually through weep holes or other designed exit points in the flashing or threshold system.
Materials Used for Pan Flashing
Pan flashing can be made from various materials, including:
Metal: Aluminum or galvanized steel are common choices due to their durability and resistance to corrosion.
Plastic or Vinyl: These materials are often used because they are cost-effective and easy to install.
Flexible Flashing Tapes: These are adhesive-backed materials that can conform to various surfaces and shapes, creating a tight seal.
Composite Materials: These may include combinations of plastics and rubbers or other synthetics that offer flexibility, durability, and resistance to moisture.
Installation Considerations
The effectiveness of pan flashing hinges on correct installation. Key points include:
Proper Sizing and Fit: The pan flashing must fit the dimensions of the door opening accurately to ensure complete coverage where water intrusion might occur.
Sealing and Integration: All joints and seams in the pan flashing should be sealed and integrated with the rest of the building's moisture barrier system. This includes overlapping with wall flashing and ensuring that any water directed away from the door will continue away from the building structure without interruption.
Positioning: The pan must be sloped slightly towards the exterior to facilitate water drainage.
Importance in Construction
Using pan flashing for exterior doors is considered a best practice in both residential and commercial construction. Building codes in many areas now require some form of pan flashing for new constructions or when major renovations are undertaken, due to the critical role it plays in moisture management.
In conclusion, pan flashing is a fundamental element for protecting a structure from water damage around doorways. It is an integral part of a comprehensive approach to weatherproofing a building, ensuring that doorways remain both functional and structurally sound over time.
