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Water Managed Roof-Wall Intersections in Existing Homes

Scope

Existing wall-to-lower roof transition retrofitted with a new strip of fully adhered air control transition membrane, new step flashing, new roof underlayment, and new cladding
Existing wall-to-lower roof transition retrofitted with a new strip of fully adhered air control transition membrane, new step flashing, new roof underlayment, and new cladding

Install and properly integrate flashing at the intersection of an existing wall and an existing intersecting roof, as follows:

  • Inspect the wall and roof framing to verify existing conditions and develop specific detailing for flashing the intersection of the wall and roof.
  • If the existing sidewall-roof intersection did not include a kick-out flashing, carefully inspect the side wall at the roof eave for deterioriation from bulk water leakage and repair as needed
  • Provide continuous water, air, vapor and thermal control layers between an existing wall and an intersecting roof with new roof underlayment, step and kick-out flashing, and cladding.

Installation of new step and kick-out flashing where an existing roof meets an existing wall should be done as part of a roof replacement. It can also be done as a stand-alone retrofit measure or as part of an exterior wall upgrade.

For more on roof/wall connections, see the U.S. Department of Energy’s Standard Work Specifications.

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

The fundamental principle of water management is to shed water by layering materials in such a way that water is directed downwards and outwards out of or away from the building. The key to this fundamental principle is drainage. Drainage applies to assemblies such as walls, roofs, and foundations as well as transitions to those assemblies such as lower roofs, porch roofs, decks, balconies, railings, and dormers.

The most elegant expression of the concept of drainage is flashing. Flashing is the most underrated of building enclosure components and arguably the most important. Metal flashing and self-adhesive flashing tapes protect vulnerable building components and help direct water down and out of the building (see Figure 1). They should be integrated with roof and wall drainage planes and water control layers, such as house wrap or building paper, in shingle fashion.

The down and out approach to flashing – metal flashing directs water down and out of building assemblies
Figure 1. The down and out approach to flashing – metal flashing directs water down and out of building assemblies. (Image courtesy of Building Science Corporation).

Step flashing is used where a sloped, shingled roof intersects a vertical wall. The metal flashing pieces are bent at a right angle with half of the flashing against the wall and the other half interwoven with or underneath the shingles of the abutting roof. The upturned leg of the step flashing is behind the vertical drainage plane (house wrap) on the wall or sealed to it with an adhesive membrane and sheathing tape. The bottom leg of the step flashing is placed over the roof drainage plane. The pieces of step flashing are laid in an overlapping shingle fashion along the length of any roof sections that intercept walls. These water control details are shown in Figures 2 and 3. In Figure 2 the roof is insulated on the underside of the roof deck with spray foam insulation. In Figure 3 the attic is insulated along the attic floor with spray foam and blown fibrous insulation but the spray foam extends up along the side wall and under the roof sheathing to provide additional air sealing to this transition.

A critical component of step flashing is the kick-out flashing. The kick-out flashing is a piece of flashing at the bottom of a section of roof that adjoins a wall. It is installed to direct water run-off away from the adjoining wall and usually into a gutter. Kick-out flashing is sometimes fabricated on site by the roofing contractor; however, seamless plastic flashing pieces specifically molded to serve as kick-out flashing pieces are available. These are sized to handle the larger volumes of water runoff that may be concentrated along the wall in rain storms. For more information, see the guide Step and Kick-out Flashing at Roof-Wall Intersections.

Installation of new step and kick-out flashing where an existing roof meets an existing wall should be done as part of a roof replacement. It can also be done as a stand-alone retrofit measure or as part of an exterior wall upgrade.

Effective transitions in a wall-to-roof intersection have been particularly problematic in high-performance and retrofit projects because the proper location and sequencing for roof-to-wall flashing requires careful coordination between contractors and roofing subcontractors to implement details that are different than may typically be done in conventional construction and renovation. Planning and advanced preparation are required for successful implementation.

Existing wall-to-lower roof transition with a new strip of fully adhered air control transition membrane, new step flashing, new roof underlayment, and new cladding – view from eave
Figure 2. Existing wall-to-lower roof transition with a new strip of fully adhered air control transition membrane, new step flashing, new roof underlayment, and new cladding – view from eave. Closed-cell spray foam is installed at the underside of the lower roof deck as an air control layer.

Existing wall-to-lower roof with attic transition with a new strip of fully adhered air control transition membrane, new step flashing, new roof underlayment, and new cladding – view from eave
Figure 3. Existing wall-to-lower roof with attic transition with a new strip of fully adhered air control transition membrane, new step flashing, new roof underlayment, and new cladding – view from eave. Closed-cell spray foam is installed at the interior attic wall to transition the air control layer from the roof sheathing to the attic air control layer.

How to Install Water Control Flashing at the Transition of a Wall to a Lower Roof

  1. Inspect the structural integrity of the wall and the overhang. Check the framing for any deficiencies, rot, insect damage, etc. Proceed only after needed repairs are performed. Based on the findings, revise the wall and overhang assembly and review specific detailing as needed. Follow the minimum requirements of the current adopted local building code.
  2. Remove the first two rows of siding on the wall above the intersecting roof to expose the existing house wrap or building paper. Remove any existing step flashing. Remove roof shingles along the intersecting wall.
  3. Install a fully adhered air control transition membrane from the existing roof sheathing onto the face of the existing wall sheathing. Extend at least 2 inches above the future step flashing.
  4. Install the roof underlayment as the water control layer. Extend it to the existing wall and over the transition membrane.
  5. Install new kick-out and step flashing at the wall-to-roof intersection, over the transition membrane. See the guide Step and Kick-out Flashing at Roof-Wall Intersections.
  6. Install the new roofing membrane or shingles over the roof underlayment and step flashing.
  7. Lap the existing house wrap or building paper over the top of the step flashing.
  8. Terminate the step flashing with a kick-out flashing, with the kick-out flashing weather lapped with both the last straight step flashing and the side wall house wrap.
  9. Re-install the bottom rows of siding over the house wrap or building paper.

Ensuring Success

Inspect the existing wall and overhang framing for any deficiencies or water intrusion damage and make any corrections, if necessary.

Ensure the water control layer of the roof and wall assemblies is continuous.

Ensure proper lapping of building layers to shed water away from the wall and overhang assemblies.

Terminate the step flashing with a weather-lapped kick-out flashing.

Climate

Water Management

In cold climates (zones 5 and higher), install self-adhered membrane over the roof sheathing at the eaves from the edge of the roof line to > 2 feet up the roof deck from the interior plane of the exterior wall. (See the guide Heavy Membranes at Eaves in Cold Climates.)

Thermal Enclosure

The roof assembly should be designed for a specific hygrothermal region, rain exposure zone, and interior climate. The climate zones are shown on the map below, which is taken from Figure C301.1 of the 2012 IECC.

IECC climate zones
IECC Climate Zone Map

The insulation levels should be based on the minimum requirements for vapor control in the current adopted building code and the minimum requirements for thermal control in the current energy code. Table 1 provides the minimum thermal resistance (R-value) requirements specified in the 2009 IECC (ICC 2009b) and the 2012 IECC (ICC 2012b) based on climate zone for roof assemblies.

Attic Insulation Requirements per the 2009 and 2012 IECC
Table 1. Attic Insulation Requirements per the 2009 and 2012 IECC

Training

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Presentations

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Videos

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CAD Images

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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

[Guidance for Version 3.0, Rev 08 is coming soon.]

ENERGY STAR Certified Homes is a voluntary high-performance home labeling program for new homes operated by the U.S. Department of Energy and the U.S. Environmental Protection Agency. Builders and remodelers who are conducting retrofits are welcome to seek certification for existing homes through this voluntary program.

The ENERGY STAR Certified Homes (Version 3.0, Rev. 07) Water Management Checklist specifies:

3.1 Step and kick-out flashing at all roof-wall intersections, extending ≥ 4 on wall surface above roof deck and integrated with drainage plane above.

3.2 For homes that don’t have a slab-on-grade foundation and do have expansive or collapsible soils, gutters & downspouts provided that empty to lateral piping that deposits water on sloping final grade ≥ 5 ft. from foundation or to underground catchment system ≥ 10 ft. from foundation.

3.3 Self-sealing bituminous membrane or equivalent at all valleys & roof deck penetrations.

3.4 In 2009 IECC Climate Zones 5 and higher, self-sealing bituminous membrane or equivalent over sheathing at eaves from the edge of the roof line to > 2 ft. up roof deck from the interior plane of the exterior wall.

200920122015, and 2018 IRC

Section R703.8 (R703.8.5 in 2015 and 2018 IRC) Flashing.

Section R903.2 Flashing.

Section R905.2.8.3 Sidewall flashing.

Section R907.6 (R908.6 in 2015 and 2018 IRC) Flashings.

Retrofit: 200920122015, and 2018 IRC

Section N1101.3 (Section N1107.1.1 in 2015 and 2018 IRC). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

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

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References and Resources*

  1. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2009

    Code for residential buildings that creates minimum regulations for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences.

  2. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2012

    Code for residential buildings that creates minimum regulations for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences.

  3. Author(s): Lstiburek
    Organization(s): Building Science Corporation
    Publication Date: January, 2006

    Book presenting the best techniques for energy and resource efficient residential construction in the colder climates of North America.

  4. Author(s): Building Science Corporation
    Organization(s): Building Science Corporation
    Publication Date: May, 2009

    Brochure providing information about flashing.

  5. Author(s): Pettit, Neuhauser, Gates
    Organization(s): Building Science Corporation
    Publication Date: July, 2013

    Guidebook providing useful examples of high performance retrofit techniques for the building enclosure of wood frame residential construction in a cold and somewhat wet climate.

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

Last Updated: 12/22/2015