Water intrusion at entry doors is the movement of water into the exterior wall assembly through openings around doors.
Door openings are vulnerable areas, because they interrupt the continuity of the drainage plane. To help prevent water intrusion, door openings have to be properly flashed and sealed.
Preparing the entry door to create a flange
Entry doors are particularly susceptible to water intrusion, because door manufacturers don't provide an integrated nailing fin. In contrast, manufactured windows include a 1 ½" nailing fin that runs along the perimeter and has holes every 4" to 6"; nails are driven through the holes in order to attach the window to the wall. Besides helping to attach the window, the nailing fin also allows the window to be sealed to the housewrap by providing a surface for flashing tape to seal the gap between the two materials.
On a door, the brick mold is used to attach the door to the wall. Brick mold, though, is thicker than the nailing fin on a window. Because of its thickness, it's very difficult to apply flashing tape over the gap between the brick mold and the housewrap. Because this area is so difficult to flash, a flange has to be created and added to the door.
Roll flashing is used to create the flange, which acts as a surface that helps to bridge the gap between the brick mold and the housewrap. This flange is thinner than brick mold, much like the nailing fin on a window, which makes it easier to layer flashing over the flange and housewrap. Without a flange, there's no way to direct water away from the door opening. It's important to note that the roll flashing isn't acting as flashing; rather, it's being used only to create a flange. Using caulk without roll flashing isn't sufficient to seal a door assembly.
Flashing the entry door
Once the flange has been created with roll flashing, it's time to install the door and flash it. Using the proper flashing pieces, including a sill pan, jamb flashing, drip cap, and head flashing, helps combat water intrusion. A sill pan provides seamless protection at the corners and guides water to the exterior. The integrated back dam provides an extra barrier to water intrusion. Jamb and head flashing help maintain the continuity of the drainage plane, so water doesn't enter the rough opening. A drip cap drains water away, instead of allowing it to sit on top of the door frame; water that sits on the door frame can lead to water intrusion around the door opening.
Cause 1:
Roll flashing at jamb molding not installed
Door manufacturers don't make doors with an integrated nailing fin. Without a nailing fin, there isn't a material to flash against in order to maintain the continuity of the drainage plane. Don't rely on just caulk to protect the home from water intrusion. Caulk deteriorates over time with exposure to the elements and is dependent on the homeowner for maintenance.
Solution
Use roll flashing to create a flange for the door. Before installing the door, cut a piece of roll flashing, so it's at least 4" wide and long enough to extend 2" above the brick mold and 3" below the door threshold. Run a bead of sealant along the backside of the brick mold. Apply the flashing against the mold and sealant, and fasten it with staples.
Cause 2:
Lack of sill pan under threshold
One location that's prone to water intrusion is the door assembly. Often, the weatherstripping or the threshold doesn’t create an effective seal, allowing water to pass through. Without a sill pan under the threshold, water will enter the wall cavity through the door assembly.
Solution
Before the door is installed, install a sill pan. Follow the manufacturer's instructions for installation. Install a two-piece sill pan, sealing the lap of the sill pan with flashing tape. Layer the housewrap over the sides of the sill pan.
Cause 3:
Lack of jamb and head flashing
Since entry door systems come with a brick mold instead of a nailing fin, they are often installed without flashing, making them more prone to water intrusion. A different flashing strategy is necessary than with windows.
Solution
Follow the proper cutout sequence for the housewrap. Layer the jamb flashing over the roll flashing and housewrap; also layer it over the sill flashing, and extend down past it. After installing the door system, apply the jamb flashing. Then, install the drip cap and head flashing, folding the housewrap down over the entire assembly.
Cause 4:
Lack of drip cap
If a preformed drip cap isn't installed and properly integrated with the flashing and housewrap, water can rest on top of the door frame instead of draining away, potentially leading to water intrusion around the door opening.
Solution
Before installing the drip cap, make sure the housewrap is folded up and out of the way, so the drip cap and flashing can be placed underneath it. Install a preformed aluminum drip cap over the brick mold, with the vertical leg attached to the wall. Then, install the head flashing, and fold the housewrap down over both materials.
ProTip!Use construction tape or flashing tape to hold the housewrap out of the way.
