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Look for Missing Window and Door Flashing

Materials Cost: FREE
Difficulty Level: 1

Introduction

Missing flashing around doors and windows can lead to water infiltration and major damage and rot that is hidden inside of the wall.

Why

Missing window flashing can let water infiltrate the walls of your home, causing hundreds or thousands of dollars worth of damage if left unchecked. Window flashing in the form of waterproof tape and metal strips should be installed around windows at installation to create a barrier against water intrusion at vulnerable junctions around doors and windows. If the flashing is missing or incorrectly installed, water can enter the wall assembly causing mold and rotting of wall sheathing, framing, and insulation. 

What You'll Need

  • Ladder or step stool
  • Gloves (optional)
  • Exterior-grade caulk
  • Flathead screwdriver (optional)

1. Examine tops of windows and doors.

The job of flashing is to direct any water that gets past the siding down and out of the walls of your home before it can cause damage (Figure 1). A properly installed window or door will have numerous layers of flashing under and over the house wrap layer to help direct water out of the wall (Figure 2). Unfortunately, without taking off the window trim or cutting into the siding, it’s hard to see whether or not flashing has been installed. The only flashing you can usually see on an installed window is the metal head flashing (in Figure 3 it is the strip along the very top of the window trim, painted white to match the trim). Note it’s preferable if the metal head flashing sticks out slightly to the left and right of the top of the window trim, the horizontal part of the flashing should angle down slightly, and the vertical “tail” should angle out away from the window frame to provide a drip edge for rain water away from the face of the window. Aside from looking for this metal head flashing, there are some signs you can look for which may indicate water leaks and deterioration beneath the siding. 

The “down” and “out” approach to flashing – metal flashing directs water down and out of building assemblies
The “down” and “out” approach to flashing – metal flashing directs water down and out of building assemblies
The “down” and “out” approach to flashing – metal flashing directs water down and out of building assemblies
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Reference
Understanding Drainage Planes, BSD-105
Author(s)
Lstiburek Joseph W
Organization(s)
Building Science Corporation,
BSC
Description

Guide providing information about controlling rainwater through use of drainage planes.

Figure 1. The “down” and “out” function of flashing – metal flashing directs water down and out of wall assemblies (Source: Building Science Corporation 2007).
This drawing shows key head details for a window installation using a self-adhered membrane tape flashing on a wall with a mechanically attached water and air control layer
This drawing shows key head details for a window installation using a self-adhered membrane tape flashing on a wall with a mechanically attached water and air control layer
This drawing shows key head details for a window installation using a self-adhered membrane tape flashing on a wall with a mechanically attached water and air control layer
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Courtesy Of
BSC
Figure 2. This drawing shows several flashing layers around a properly installed window, including flashing tapes, and metal head flashing, properly integrated with the mechanically attached water and air control layer (i.e., house wrap) (Source: Building Science Corporation).
Figure 3. The metal head flashing over the window trim angles out slightly to provide a drip edge so rain water will drop away from the window instead of rolling down onto the window trim (Source: PNNL).

2. Examine the window and door trim.

If the window trim is showing signs of rot or peeling paint, a poorly draining window may be the cause. Check to make sure the weep holes in the bottom frame of the window have not been caulked or painted over. A lack of flashing around and above the window could also contribute to the deterioration of the trim. To check your trim, take a screwdriver or your thumbnail and push into the wood. The wood should be firm. If you can easily press into the wood, that is a good indication of dry rot and water issues beneath. Figure 4 shows a situation where water damage was suspected so newer siding that had been installed over old siding was cut away revealing that no flashing had been installed and the old siding beneath had become saturated from repeated exposure to rainwater that had leaked in around the window. 

Figure 4. New siding was installed over old siding, but no flashing or trim was installed and the old siding became saturated when water leaked around the windows (Source: PNNL)

Peeling paint on the trim around an exterior door, especially just at the base of the door, could indicate water entering the wall from above or around the door due to lack of flashing, or be due to splash-back from rain (if there are no gutters overhead) or snow build up in that spot that continually saturates the wood trim. A related issue is door trim that was installed without priming or painting the cut ends at the base of the side trim. If these ends have ground contact, the bare wood on the grain end can pull water up into the lumber through capillary action. Then, when the wood dries in the sun, the water vapor coming out of the wood can lift the paint right off the wood’s surface.

3. Examine the siding.

Examine siding under or around windows and doors. Look for cracks, warping, peeling paint, discoloration, rotting, algae, or mold formation. All of these could be signs of water damage underneath the siding (Figures 5, 6, 7, and 8). 

Wrong - Wiring holes are not sealed and possible missing flashing around windows is allowing water into walls and causing paint to peel.
Wrong - Wiring holes are not sealed and possible missing flashing around windows is allowing water into walls and causing paint to peel.
Wrong - Wiring holes are not sealed and possible missing flashing around windows is allowing water into walls and causing paint to peel.
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Figure 5. Peeling paint on these walls is indicative of water damage and possible intrusion into the wall (Source: PNNL).
Figure 6. New windows were installed in this home but nothing was done to repair the rotted sill or to address why it failed (Source: Building Science Corporation).
Wrong - Water has gotten behind the paint, possibly due to lack of window flashing, leading to blistering.
Wrong - Water has gotten behind the paint, possibly due to lack of window flashing, leading to blistering.
Wrong - Water has gotten behind the paint, possibly due to lack of window flashing, leading to blistering.
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Figure 7. Water has gotten behind the paint, possibly due to lack of window flashing, leading to bubbling of the paint on the lap siding of this home (Source: PNNL).
Figure 8. Bubbling, blistering, and peeling paint can be a sign of moisture damage in the wall beneath; when damp wood or fiber cement siding dries in the sun, the water vapor leaving the wall can lift the paint off the walls (Source: PNNL).

4. Check inside the home.

Visible water stains on walls or ceilings are obvious signs of water leaks. Also look for cracking or bubbling of paint beneath windows. Look for unexplained dampness in carpets along exterior walls. Carpenter ants inside the home can be another indication of damp wood somewhere in the home. Visible mold on walls or a moldy or mildew smell can also indicate a moisture problem somewhere in the walls. The cause of moisture issues like these should be investigated – it could be rainwater intrusion due to lack of flashing or poor wall or roof detailing, or it could be due to a plumbing leak, foundation water management issues, or a significant need for ventilation and dehumidification. 

5. If re-siding or replacing windows, check the sheathing and framing behind the siding and trim.

If all or part of your house is being re-sided, or if windows are being replaced and the trim is off, then it is an optimal time to check for signs of moisture issues around your windows.

  1. Look for the window and door flashing before new siding is installed to ensure that flashing is present, correctly installed, and properly integrated with house wrap to direct water out and away from wall cavities.
    1. Check for pan or sill flashing at the bottom of window openings (note the sill flashing should be angled to drain water out of the window).
    2. Ensure flashing tape is installed vertically along the edges of the window or door opening (the jambs) and properly lapped under the head flashing, and over the sill (pan) flashing. (Figure 9).
    3. Ensure flashing tape (or metal for older construction) at the top of the opening (head flashing) is layered over the drip-cap flashing and over the jamb tape (or metal) along the sides of the opening (Figure 10).
    4. Do NOT seal “weep holes” at the bottom of windows, as these are designed to allow moisture out of the window if it gets behind the glass.
  2. Install new house wrap if needed. The house wrap should be underneath flashing at sides and bottom of windows and overlap door and window tape flashing at the tops. Proper integration of the house wrap with the windows is best achieved by removing and reinstalling the windows. 
  3. Do not ignore signs of moisture damage (mold, deteriorating lumber or sheathing, wet insulation, etc.) Work with a contractor to identify and fix the source of the water leaks in addition to just repairing the damage.
Figure 9. This window is properly flashed, with pan flashing installed before the window is placed, then side (jamb) flashing over the window flanges, then flashing across the top, then folding down the house wrap flap that had been tacked up before inserting the window, then additional head flashing will be installed (Source: Building Science Corporation 2007).
Install trim and cap flashing
Install trim and cap flashing
Install trim and cap flashing
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Source
Reference
READ THIS: Before You Design, Build or Renovate, GM-0602
Author(s)
Brennan Terry,
Lstiburek Joseph W
Organization(s)
Building Science Corporation,
BSC
Description

Document with important building science considerations, designed for members of the residential construction and remodeling industries, as well as owners and managers who work in affordable housing.

Figure 10. Install trim and cap flashing above the window (Source: Building Science Corporation 2005).

Additional Info

References

READ THIS: Before You Design, Build or Renovate, GM-0602

Publication Date
·
Author(s)
Brennan Terry,
Lstiburek Joseph W
·
Organization(s)
Building Science Corporation,
BSC
Description
Document with important building science considerations, designed for members of the residential construction and remodeling industries, as well as owners and managers who work in affordable housing.

Guide to Insulating Sheathing

Publication Date
·
Author(s)
Building Science Corporation
·
Organization(s)
BSC
Description
Guide providing information on using exterior foam insulating sheathing in building wall assemblies to enhance thermal performance.
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Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.