Threshold and Pan Flashing
The drawing above illustrates the 1-1/4” tall extruded aluminium threshold installed directly to a concrete slab at an in-swing door. The inside leg has been trimmed 3/8” to fit over a wood or tile floor surface. The door above it is 1-3/4” thick and has been trimmed to create the proper spacing needed to work with the vinyl door bottom. The bottom of every exterior door must be sealed before applying any weatherstrip material to prevent the absorption of moisture that would shorten its life span.
Pan flashing is the primary defense in prevention of water damage at exterior openings that are most vulnerable to the elements. Although we do not manufacture or install pan flashing at door openings, we feel obligated to inform our customers of their necessity in certain conditions. Exterior door openings with wood subflooring, typically a second floor application, must be properly flashed to create a protective water barrier. This pan flashing must be installed prior to the door unit installation allowing the jamb legs to set within its perimeter. It is typically made from galvanized sheet metal and is custom fit on site by its manufacturer. The absence of pan flashing where required can result in major damage to the subflooring and framing beneath it. The water damage may also spread to the ceiling of the living space below and become an expensive problem to repair involving multiple trades. The absence of pan flashing where necessary will void our warranty due to almost certain damage that will occur later. Please insist that your builder or contractor uses pan flashing before your door units are installed at any opening not having a concrete slab base.
The illustration above shows the proper construction principles used to insure a waterproof door unit installation at a typical second floor balcony opening. Please note the sloped balcony surface is constructed at an elevation lower than the interior sub floor surface. This prevents water on the balcony surface from entering the living space. The balcony surface is flashed with an upturned edge at the outside face of the door opening. It is then overlapped by the down turned front edge of the pan flashing. After the door unit is set inside the pan and secured in the opening it will then be ready for the threshold and weatherstripping.
The enlarged detail above illustrates the design of the pan flashing along with the correct threshold installation. Please note how the front and middle leg of the threshold are on top of the pan surface with the flashing turned up just inside of the middle (caulking) leg to insure no water gets to the interior finishes. The pan should also extend up the face of the framing studs at least four inches to protect the studs and the bottom plate from moisture.
We hope this introduction to thresholds and weatherstripping has helped you to understand the importance of using the proper materials and construction practices in sealing the door openings at your home or business from the elements. It is much wiser to be pro-active than re-active when building or remodeling your home.
Once again, please contact us if you have any questions about your project. We will be glad to assist you. Phone # (713) 869-6466.