Fully Flashed Window and Door Openings

Scope

Install insulating foam sheathing and tape all seams to serve as a continuous drainage plane behind the home’s cladding.
Install insulating foam sheathing and tape all seams to serve as a continuous drainage plane behind the home’s cladding.

Install properly lapped flashing around window and door openings to direct water out, not into the wall cavity.

  • Install rigid, flexible, or fluid-applied pan flashing at sills.
  • Install window or door.
  • Install side flashing that extends over the pan flashing.
  • Install top flashing that extends over the side flashing.
  • Properly integrate all flashing with the drainage plane layer (which could be house wrap, taped weather-resistant sheathing, a liquid-applied coating, or another approved material).

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

Description

Windows and doors are an interruption in the wall’s house wrap or insulated sheathing drainage plane and thus are a vulnerable spot for water leakage. Many a homeowner has suffered from water intrusion around doors and windows, often not discovered until considerable damage has been done within the wall. The wall framing around windows and doors must be protected from any water that finds its way behind the siding at these locations and the water must be directed out to prevent damage to the rest of the wall. Properly installed flashing that is integrated with the other elements of the wall can help prevent water damage. 

Flashing materials may be installed by insulators, framers, or subcontractors or vendors hired specifically to install the windows and doors. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job site.

Other Considerations: When designing the home, walls and doors should be located under overhangs or porch roofs whenever possible; these features protect against rain and snow and also minimize unwanted solar heat gain by blocking out high summer sun.
 

How to flash windows and doors

  1. Cut the housewrap covering the rough opening in the shape of a modified "I." See Figure 1.
    • Fold the side and bottom flaps into the window opening and secure.
    • Above the window opening, cut a head flap. Fold it up to expose the sheathing and loosely tape it in place out of the way.

    Cut I in housewrap

    Figure 1 - Cut an I in the house wrap over the window rough opening. Reference

  2. Install back dam and self-adhesive flashing at sill. Tape the corners. See Figure 2.

    Install self-adhesive sill flashing

    Figure 2 - Install self-adhesive sill flashing in the window rough opening. Reference

    For pan or sill flashing, use formable flashing, a stretchable self-adhered membrane that bends at corners so one continuous piece can be used to cover the bottom and sides of the sill.

    • First install a back dam consisting of a strip of wood or beveled siding nailed along the back (inside) edge of the rough opening (over the flap of housewrap). Sloped pans are required if the sill depth is greater than 6 inches according to ASTM E212207. 
    • Cover this with the membrane. Begin pressing in the middle of the sill and work toward the sides, removing adhesive covering strips as you go. Make sure to press the membrane tightly into the corners to avoid tears later when the window is installed.

    Other options for pan flashing include self-adhered non-elastic membrane (se Figure 3), which must be cut and patched at corners, two-piece rigid manufactured pan flashing, which comes with a built-in back dam that must be protected from breakage during window installation, or asphalt-based liquid flashing that is applied with a paint brush or roller.

    Pan flashing

    Figure 3 - Three types of window pan flashing with back dams. Reference

  3. Caulk the outside edges of the head and side jambs and install the window. See Figure 4.
    • Do not caulk across the sill.
    • Install the window plumb, level, and square following manufacturer’s specifications.

    Caulk top and sides of window

    Figure 4 - Caulk the top and sides of the window rough opening, but not the bottom. Reference

  4. Install jamb and head flashing. See Figure 5.
    • Install self-adhesive jamb flashing extending 4 inches above the top of the head flange and even with the bottom of the sill flashing.
    • Install self-adhesive head flashing extending 1 inch beyond the jamb flashing.
    • Unfold the housewrap and lay over the head flashing. Tape bottom edge of housewrap across the top window flange and tape down corner seams of housewrap. See Figure 6.

    Flash sides and top of window

    Figure 5 - Flash the sides and top of the window. Reference

    Tape down housewrap head flap

    Figure 6 - Tape down the housewrap head flap. Reference

  5. On the interior side of the window, seal the gap between the window and the rough opening with backer rod or non-expanding foam and caulk. See Figure 7.

    Air seal rough opening from inside

    Figure 7 - Air seal the rough opening around the window from the inside. Reference

  6. Install trim that has been painted or primed on all sides. Above top trim, install cap flashing that extends past trim. Cover top edge of cap flashing with adhesive membrane strip. Cover top edge of membrane with sheathing tape. See Figure 8.

    Install trim and cap flashing

    Figure 8 - Install trim and cap flashing above the window. Reference

How to Flash a Door

  1. Flash the door head and jambs as described above for windows or in accordance with the door manufacturer’s instructions.
  2. For sill flashing, see the door manufacturer’s instructions.
  3. For houses with concrete slab floors, form a seat in the concrete slab to act as a “pan flashing.” See Figure 9.

Concrete slab pan flashing for doors

Figure 9 - A sea is formed in the concrete slab to act as pan flashing for a door. Reference

  1. Install pan flashing that is integrated with the housewrap. ASTM E2112-07 recognizes several flashing materials and methods, including single-piece sill pans formed from rigid sheet metal (see Figure 10) , multi-piece sill pans formed from rigid sheet metal or plastic, flexible membrane, or combinations of rigid corners connected by flexible membrane.

Sheet metal pan flashing for doors

Figure 10 - Sheet metal pan flashing for doors. Reference

Ensuring Success

Visually inspect the window and door flashing before siding is installed to ensure that flashing is correctly installed and correctly integrated with sheathing and housewrap to direct water out and away from wall cavities.

Climate

No climate-specific information applies.

Training

Right and Wrong Images

Presentations

None Available

Videos

  1. Building Enclosure: Exterior Wall Overview
    Author(s): NAHB Research Center
    Organization(s): NAHB Research Center
  2. Building Enclosure: Window Installation
    Author(s): NAHB Research Center
    Organization(s): NAHB Research Center
  3. Building Enclosure: Exterior Door Installation
    Author(s): NAHB Research Center
    Organization(s): NAHB Research Center
  4. Building Enclosure: Stone Veneer Installation Interior Drainage Plane
    Author(s): NAHB Research Center
    Organization(s): NAHB Research Center
  5. Fully Flashed Window and Door Openings (1)
    Publication Date: July, 2015
    Courtesy Of: Train2Build

    Video describing how to properly flash window and door openings.

  6. Fully Flashed Window and Door Openings (2)
    Publication Date: September, 2015
    Courtesy Of: DuPont

    Video describing how to fully flash window and door openings.

CAD Images

None Available

Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

ENERGY STAR Certified Homes

ENERGY STAR Certified Homes (Version 3/3.1, Revision 08), Water Management System Builder Requirements

2. Water-Managed Wall Assembly: 

2.3 Window and door openings fully flashed.11

Footnotes:

(11) Apply pan flashing over the rough sill framing, inclusive of the corners of the sill framing; side flashing that extends over pan flashing; and top flashing that extends over side flashing or equivalent details for structural masonry walls.

Builders Responsibilities:  It is the exclusive responsibility of builders to ensure that each certified home is constructed to meet these requirements. While builders are not required to maintain documentation demonstrating compliance for each individual certified home, builders are required to develop a process to ensure compliance for each certified home (e.g., incorporate these requirements into the Scope of Work for relevant sub-contractors, require the site supervisor to inspect each home for these requirements, and / or sub-contract the verification of these requirements to a Rater). In the event that the EPA determines that a certified home was constructed without meeting these requirements, the home may be decertified. 

ENERGY STAR Revision 08 requirements are required for homes permitted starting 07/01/2016.

DOE Zero Energy Ready Home

Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3.

FMA/AAMA 100-07

FMA/AAMA 100-07. Standard Practice for the Installation of Windows with Flanges or Mounting Fins in Wood Frame Construction. Available from AAMA’s online store from the link above. The standard covers the installation of windows in new construction using a membrane/drainage system and the installation process for windows from pre- to post-installation and windows that use a mounting flange or fin attached and sealed to the window perimeter frame and designed as an installation fastening appendage. Minimum requirements for window installation based on current best practices are also provided.

ASTM E-2112-07

ASTM E-2112-07. Standard Practice for Installation of Exterior Windows, Doors and Skylights. The standard covers fenestration product installation from pre-installation through post-installation procedures in new and existing construction.

2009 IRC

Section R703.8 Flashing. Approved corrosion-resistant flashing to be applied shingle-fashion to prevent water from entering into wall cavities or from penetrating into building structural framing components. Self-adhered flashing must comply with AAMA 711. Flashing at exterior window and door openings must extend to the surface of the exterior wall finish or to the water-resistive barrier.

2012 IRC

Section R703.8 Flashing. Approved corrosion-resistant flashing to be applied shingle-fashion to prevent water from entering into wall cavities or from penetrating into building structural framing components. Self-adhered flashing must comply with AAMA 711. Flashing at exterior window and door openings must extend to the surface of the exterior wall finish or to the water-resistive barrier. Flashing must be installed in accordance with one or more of the following:

  • In accordance with fenestration manufacturer’s installation and flashing instructions or in accordance with the flashing manufacturer’s instructions. Where instructions or details aren’t provided, pan flashing is to be installed at the sill of exterior window and door openings and must be sealed or sloped to direct water to the surface of the exterior wall finish or water-resistive barrier. Openings using pan flashing must also incorporate flashing or protection at the head and sides.
  • Per the flashing design or method of a registered design professional.
  • Under other approved methods.*

*Due to copyright restrictions, exact code text is not provided.  For specific code text, refer to the applicable code.

IRC 2015

Section R703.4 Flashing. Approved corrosion-resistant flashing to be applied shingle-fashion to prevent water from entering into wall cavities or from penetrating into building structural framing components. Self-adhered flashing must comply with AAMA 711. Fluid-applied membrane flashing must comply with AAMA 714. Flashing must be installed in accordance with manufacturer’s instructions or as follows: Pan flashing at exterior window and door openings must direct water to the surface of the exterior wall finish or to the water-resistive barrier. Openings with pan flashing should also have flashing at the head and sides.

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

SCOPE

Retrofit rough openings of windows and doors with new flashing prior to the installation of new or rehabilitated windows and doors.

  • Evaluate building conditions for hazards and damage; correct as needed before proceeding.
  • Identify concerns (water infiltration, air leakage, heat loss) and rank them to determine the project goals.  
  • If appropriate, remove the existing windows or doors, as well as adjacent trim and cladding, and prepare the rough openings for new flashing as outlined in the Description tab.

For more information on conditions that may be encountered when working with walls in existing homes, see the assessment guide on walls, windows, and doors.

See the U.S. Department of Energy’s Standard Work Specifications for more on installing and replacing windows. Follow safe work practices as described in the Standard Work Specifications.

DESCRIPTION

Unless a home owner is pursuing a deep energy retrofit that involves removal of the cladding to add exterior insulation, window and door retrofits often do not address water management of the rough opening, apart from simply caulking the new window or door to the existing trim, which is left in place. While not best practice, this limited type of window retrofit (which does not address the rough opening) is often carried out successfully, especially if the trim is painted and in good condition, the sill trim is sloped to the exterior, and the wall retains its ability to dry after the retrofit. The risk of water problems such as leaking and rot increases at windows with high exposure to wind and rain, damaged or improperly sloped sills, and when the wall’s ability to dry is decreased (with the addition of cavity insulation, for example). Figure 1 shows a new window installed in a wall with a failed rotting window sill. Air and water leakage will likely soon occur around this window if it hasn’t already started.

A new window was installed without repairing the failed window sill first
Figure 1. A new window was installed without repairing the failed window sill first. Image Courtesy of Building Science Corporation. 

Best practice when replacing windows is to remove the trim and flash the rough opening for drainage and durability per the concepts outlined in the Scope and Description tabs.  There are several Solution Center guides describing measures that can be taken to improve water management, comfort, and energy efficiency with windows, ranging from repair and refurbishment to adding storm windows, to full replacement. Also see the report “Measure Guideline: Wood Window Repair, Rehabilitation, and Replacement” by Building Science Corporation.

How to Flash Existing Windows and Doors

  1. Evaluate building conditions for hazards and damage that should be corrected before proceeding such as the presence of lead paint or water intrusion from sources other than the window.
  2. Identify existing window and door performance concerns (water infiltration, air leakage, heat loss) and rank them to determine the project goals so that the appropriate retrofit measures may be selected, from minor repairs to full removal and replacement.
  3. If full removal is appropriate, remove the existing windows or doors as well as adjacent trim and cladding, and prepare the rough openings with new flashing in accordance with the steps outlined in the Description tab.

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Case Studies

  1. Author(s): PNNL
    Organization(s): BSC, PNNL
    Publication Date: September, 2013

    Case study about a DOE Building America 2013 Top Innovation on upgrading or replacing windows in existing homes, based on research by Building America research partner Building Science Corporation..

  2. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: April, 2012

    Case study about a home builder that has refined its home designs to achieve HERS scores of 49 to 56 on 40 to 70 homes per year.

References and Resources*

  1. Author(s): Baechler, Gilbride, Hefty, Cole, Love
    Organization(s): PNNL, ORNL
    Publication Date: February, 2011
    Guide describing measures that builders in the cold and very cold climates can take to build homes that have whole-house energy savings of 40% over the Building America benchmark with no added overall costs for consumers.
  2. Author(s): DOE
    Organization(s): DOE
    Publication Date: April, 2017

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  3. Author(s): EPA
    Organization(s): EPA
    Publication Date: December, 2015

    Document outlining the program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 08).

  4. Author(s): Grin, Lstiburek
    Organization(s): BSC
    Publication Date: September, 2014
    Measure Guideline research report providing simple, long term, and durable solutions when using tapes and flashing membranes in conjunction with the exterior face of rigid polymeric foam sheathing to create the drainage plane of a wall system.
  5. Author(s): Baker
    Organization(s): BSC, NREL
    Publication Date: December, 2012

    Document providing information and guidance about rehabilitating, retrofitting, and replacing wood window assemblies in residential construction.

  6. Author(s): BSC
    Organization(s): BSC
    Publication Date: May, 2009
    Information sheet with details on pan flashing for exterior walls.
  7. Author(s): Building Science Corporation
    Organization(s): BSC
    Publication Date: January, 2014
    Case study about how to properly tape insulating sheathing drainage planes.
  8. Author(s): BSC
    Organization(s): BSC
    Publication Date: November, 2007
    Document providing guidance on water management concepts and applications.
  9. Author(s): EPA
    Organization(s): EPA
    Publication Date: February, 2011
    Guide describing details that serve as a visual reference for each of the line items in the Water Management System Builder Checklist.

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Building Science Corporation, lead for the Building Science Consortium (BSC), a DOE Building America Research Team
Home Innovations Research Labs, lead for the Partnership for Home Innovation (PHI), a DOE Building America Research Team

Last Updated: 06/16/2017

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