TAG Tech Talk Building Flashings

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1Building Exterior Facades are intended to prevent water from entering into the building. Building facades are comprised of an exterior skin which is hung on the building frame. Windows, doors, louvers and lighting fixtures penetrate the building skin. At each of these locations exterior seals are required to prevent water infiltration in to the structure. Exposed to inclement weather all building facades and roofing materials deteriorate over time. Building leaks are inevitable in all structures and the question is not “if” a building will leak but “when”.

2Restoration of a failed wall system is unique to each building. Parameters which need to be considered when investigating water intrusion issues are improper structural or architectural design, improper installation of materials and incompatibility of building materials. A flashing failure at one location may allow moisture to travel a considerable distance from it point source before it actually leaks in to the building. Water intrusion can cause damage such as spalling, freeze / thaw deterioration, rusting and corrosion of metals. This damage often leads to an increase in water infiltration as well as spreading water leaks at new locations. The process will continue to grow until it is resolved.

Note: Integrating the masonry facade and flashing materials together is one of the most challenging aspects to a good design for the exteriors wall to resist water entering the building. It is difficult, to next to impossible to determine how well a wall will perform considering only the properties of the materials.

3Suggested Inspection Evaluations should include:
1. Preliminary Investigation of building façade and roof
2. Review of building drawings and leak history
3. Perform water testing and dye evaluations
4. Perform open wall cavity inspections ( shelf angle and headers)
5. Identify failed sealant or poor masonry substrates
6. Review parapet cap condition and interior roof membrane
7. Moisture test porosity of masonry skin
8. Inspect flashing end dams and seam adhesion

Flashing is an integral component to any building wall or roof. The purpose of flashing is to prevent water from passing from a wet area to a dry area. Flashing are installed at all through wall or roof penetrations, shelf angles, roof changes in direction and at obstacles such as chimneys, vent pipes, roof and wall intersections, window and door openings.



  • Flashing may be exposed or concealed. Exposed flashing usually is a sheet metal such as lead, copper, galvanized steel, stainless steel or lead-coated copper
  • Flexible flashings include adhesive backed, rubberized, asphalt compounds which are used around wall penetrations such as window and door openings.


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