Water Managed Roof-Wall Intersections in Existing Homes
Scope
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.
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.
How to Install Water Control Flashing at the Transition of a Wall to a Lower Roof
- 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.
- 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.
- 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.
- Install the roof underlayment as the water control layer. Extend it to the existing wall and over the transition membrane.
- 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.
- Install the new roofing membrane or shingles over the roof underlayment and step flashing.
- Lap the existing house wrap or building paper over the top of the step flashing.
- 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.
- 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.
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.
Training
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, Version 3/3.1 (Rev. 09)
Water Management System Builder Requirements
3. Water-Managed Roof Assembly.
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.12
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 discharges water on sloping final grade ≥ 5 ft. from foundation, or to underground catchment system not connected to the foundation drain system that discharges water ≥ 10 ft. from foundation. Alternatives & exemptions in Footnote.3, 13, 14
3.3 Self-adhering polymer-modified bituminous membrane at all valleys & roof deck penetrations.3, 15
3.4 In 2009 IECC Climate Zones 5 & higher, self-adhering polymer-modified bituminous membrane 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. 3, 15
Footnote 12) Intersecting wall siding shall terminate 1 in. above the roof or higher, per manufacturer's recommendations. Continuous flashing shall be installed in place of step flashing for metal and rubber membrane roofs.
Footnote 14) Any of the following are permitted to be used as alternatives to Item 3.2: a) a roof design that deposits rainwater to a grade-level rock bed with a waterproof liner and a lateral drain pipe that meets discharge requirements per Item 3.2; b) a rainwater harvesting system that drains overflow to meet discharge requirements per Item 3.2; or c) a continuous rubber membrane (e.g. EPDM) that is aligned with the foundation wall from final grade to ≥ 8 in. below grade and then slopes ≥ 0.5 in. per ft. away from the home for at least 5 ft., with Group I Soils (as defined in Footnote 8) covering the membrane to within 3 in. of final grade.
Footnote 15) As an alternative, any applicable option in 2009 IRC Section R905.2.8.2 is permitted to be used to meet Item 3.3 and any option in 2009 IRC Section R905.2.7.1 is permitted to be used to meet Item 3.4. EPA recommends, but does not require, that products meet ASTM D1970. In addition, any option in 2009 IRC Section R905.13 is permitted to be used to meet either Item 3.3 or 3.4.
Please see the ENERGY STAR Certified Homes Implementation Timeline for the program version and revision currently applicable in in your state.
2009, 2012, 2015, 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: 2009, 2012, 2015, 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.
Kick-Out Flashing, Step Flashing = Roof-Wall Water Deflector
Where roofs intersect walls is a critical point for flashing to prevent water leaks and damage. While wood siding may show evidence of this water intrusion with peeling paint or staining, some wall claddings like fiber cement, vinyl siding, and brick veneer can mask the evidence for years. Flashing and diverters must be correctly integrated with house wrap, cladding, and gutters to avoid water damage.
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