Shingles lost on steep roof (C) Daniel Friedman Asphalt Shingle Installation on Very Steep or Vertical Surfaces: Roofs or Walls
     


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This article discusses best practices for the installation of asphalt roof shingles on very steep slopes such as on mansard roofs and (though not recommended) on vertical surfaces such as building walls.

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Guide to Installing Asphalt Shingles on Near-Vertical Building Surfaces or Roofs or Walls

At SIDING ASPHALT SHINGLE or SHEET we discuss the history and uses of asphalt-based building siding materials. At ROOFING INSPECTION & REPAIR and at ASPHALT ROOF SHINGLES readers can return to roofing topics.

Special nailing and sealing requirements must be met when installing asphalt-based roof shingles on very steep slopes such as A-Frame or Mansard roofs.

According to ASPHALT SHINGLE INSTALLATION where we cite Best Practices Guide to Residential Construction, Wiley (November 18, 2005), asphalt shingles should not be installed on vertical walls. In sum, we do not recommend (and have not found a building authority that currently recommends) using asphalt-based roof shingles on building walls to serve as exterior building siding.

  • Without extra nailing details asphalt shingles are more likely to fail or fall off or be blown off of the very steep roof or vertical wall surface.
  • Without extra roof shingle tab sealing, asphalt roof shingles on a very steep slope or on a vertical wall surface may fail to seal, resulting in severe wind blow-off damage in storms.

Nevertheless we have on occasion found asphalt roof shingles and occasionally mineral-granule coated roll roofing or even modified bitumen roofing nailed to vertical building walls as a low-cost siding material. Most often roof shingles are used on the walls of a temporary storage shed or clubhouse.

Watch out: If you are going to attempt to install asphalt roof shingles on a very steep slope roof or on a building wall despite these cautions, be sure that you follow the appropriate vertical and near-vertical nailing instructions for the roof shingles that we describe below. Otherwise you'll find them falling off or blowing off of the building.

Referring to slopes of 18" rise in 12" of run (150%) or more, [note that this is more cautious than Bliss's advice found at ASPHALT SHINGLE INSTALLATION] the NRCA (Flickinger) points out that there are differing views within the roofing industry about the maximum slope on which asphalt shingles may be applied using typical methods.

Shingles lost on steep roof (C) Daniel FriedmanOur steep roof photo (left) shows quite a few shingles lost from this rather steep church roof slope. Flickinger cites the NRCA Roofing and Waterproofing Manual 4th Ed. when he recommends the following steps to be taken when installing asphalt shingles on a very steep (or near vertical) roof slope [probably also helpful if installing shingles on a wall surface]:

  1. 18:12 slope shingle application: 6 nails per shingle since on a steep slope more of the shingle's weight is carried by the nails rather than the roof deck
  2. 18:12 slope shingle application: Specifications for hand sealing of roof shingles is necessary. At an extreme incline roof shingle's overlapping courses won't apply the necessary pressure to cause the adhesive strips to adequately seal the shingles to the course below.

    Hand sealing or "tabbing" roof shingles on a steep slope means applying a dab of sealant (roof cement) under each shingle. For architectural-style laminated shingles use four equally-spaced dabs of sealant under the shingle's leading (lower) edge.
    1. NRCA recommends 3 sealant dabs for 3-tab (cutout type) asphalt shingles, with each spot centered at the bottom of each shingle tab.
    2. ARMA recommends 6 sealant dabs for 3-tab (cutout type) asphalt roof shingles, with a dab at both corners of each shingle tab.
  3. 12:12 slope shingle application: (100% slope) and greater: Flickinger notes that some shingle manufacturers require special procedures including extra fasteners and hand sealing on these slopes.
  4. The UBC (Uniform Building Code) and BOCA (Building Officials and Code Administrators International) codes require following the manufacturer's instructions (no kidding, try reading the instructions on the package!) for asphalt shingles installed on the sides of mansard style roofs and on more steep roof slopes.

See these roof flashing articles:

FLASHING, ASPHALT SHINGLE VALLEYS
FLASHING MEMBRANES PEEL & STICK
FLASHING for METAL ROOFS
FLASHING ROOF WALL DETAILS
FLASHING ROOF-WALL SNAFU
FLASHING SIDING DETAILS
FLASHING WALL DETAILS
FLASHING WINDOW DETAILS
FLASHING WOOD ROOF DETAILS

Underlayment or Sheathing Wrap When Using Asphalt Roof Shingles on Walls

Just as for applying shingles to a roof, underlayment or more properly, housewrap would be recommended for use on wall surfaces just as for most other sidings. The vertical surface of a wall should be sound before installing the underlayment. Whether or not it is required, house wrap, and proper flashing details around building openings are reduce the chances of leaks.

See VAPOR BARRIERS & HOUSEWRAP. Also see HOUSEWRAP INSTALLATION DETAILS and see these underlayment articles.

UNDERLAYMENT REQUIREMENTS on ROOFS
  ROOFING UNDERLAYMENT BEST PRACTICES
    Underlayment for Standard Slopes
    Underlayment on Low Slope Shingle Roofs
    Flashing in Freezing Climates

Resources: Asphalt Roofing Materials & Equipment Suppliers

Manufacturers of Asphalt Shingles

Atlas Roofing Corp. www.atlasroofing.com Fiberglass and organic felt shingles

Certainteed Roofing www.certainteed.com Fiberglass shingles

Elk Premium Building Products www.elkcorp.com Fiberglass shingles

GAF Materials Corp. www.gaf.com Fiberglass shingles

Georgia-Pacific Corp. www.gp.com/build Fiberglass and organic felt shingles

IKO www.iko.com Fiberglass and organic felt shingles

Owens Corning www.owenscorning.com Fiberglass shingles

Tamko Roofing Products www.tamko.com Fiberglass and organic felt shingles

Low-Slope Roofing Membranes

Duradek www.duradek.com Vinyl roofing and walkable deck membrane

Firestone www.firestonebpe.com RubberGard EPDM residential roofing system

GenFlex Roofing Systems www.genflex.com Peel-and-stick TPO membrane

Hyload, Inc. www.hyload.com Kwik-Ply self-adhering polyester and coal-tar roofing membrane

More Information about Roofing Materials, Methods, Standards

Asphalt Roofing Manufacturers Association (ARMA) www.asphaltroofing.org

Cedar Shake and Shingle Bureau www.cedarbureau.org

Metal Roofing Alliance www.metalroofing.com

Tile Roofing Institute www.tileroofing.org

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