Wood shingle application (C) Carson Dunlop Associates

Wood Roof Shingle & Wood Shake Roof Installation Specifications
     

  • WOOD ROOF INSTALLATION SPECS - CONTENTS: Pitch or slope requirements for wood roofs. Nailing schedule for wood shingles/shakes. What types of nails or staples are used with wood shakes or wood shingles? What is the proper nailing pattern for wood shingle or wood shake roofs. Wood shingle exposure length table. Notes on side-lap wood shingle roofs.
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Wood shingle & wood shake roof installation specifications: this wood roof article describes the slope and exposure requirements for wood shake or wood shingle roofs, and provides detailed instructions on how and where to nail or fasten wood shingles/shakes on roofs.

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Slope and Exposure Tables for Wood Shake & Shingle Roofs

Improperly set wood shingle roof (C) Daniel FriedmanOur page top sketch is provided courtesy of Carson Dunlop Associates.

[Click to enlarge any image]

Also see WOOD ROOF SHAKES INSTALLATION and WOOD ROOF SHEATHING, UNDERLAYMENT as well as our checklist of wood shingle installation specs at WOOD ROOF INSPECTION GUIDE. As discussed in BEST ROOFING PRACTICES,

Recommended exposures for shakes and shingles on roofs are shown in Tables 2-13 and 2-14.

  • Minimum slopes. The minimum recommended slope for standard installation of shingles is 3:12, and 4:12 for shakes.
  • Low slopes. On lower slopes, shingles or shakes may be installed over a fully waterproof built-up roof (BUR) or membrane roof. Over the membrane, install vertical 2x4 battens lined up with the rafters, then spaced sheathing as described below.
  • Climate factors. In warm, high-moisture climates, lowslope wood roofs need extra maintenance, particularly in areas with overhanging trees. If pine needles, leaves, or other organic debris is allowed to accumulate on a shaded section of the roof, moss, lichen, and algae will grow and retain moisture. This, in turn, will lead to premature curling, splitting, and decay of the shakes or shingles.

    Periodic wood roof cleaning, as well as chemical treatment, helps to avoid these problems (see WOOD ROOF MAINTENANCE or see page 93 in the printed text Best Practices Guide to Residential Construction). Pressure-treated shakes or shingles are recommended in these conditions.

- Adapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:

Wood shingle head lap in a good installation exposes no more than 1/3 of the shingle to the weather. The head laps are 6", 7", or 9" respectively for 16", 18" or 24" long shingles respectively. More details are at WOOD ROOF INSPECTION GUIDE.

Wood Roof Shingle Exposure Specifications

Shingle exposures for wood roofs: the maximum weather exposure for wood shakes or wood shingles depends on the shingle size and the slope or pitch of the roof. Allowable shingle exposure may also vary by the shingle grade - something that you might infer by visual inspection of the shingles, matching against wood shingle grade definitions, or if a shingle identification label can be located.

Roof Slope or Pitch
Maximum Wood Shingle Exposure on Roofs
Grade No. 1 Blue Label Shingles
Grade No. 2 Red Label Shingles
Grade No. 3 Black Label Shingles
Shingle Length
Shingle Length
Shingle Length
16" 18" 24" 16" 18" 24" 16" 18" 24"
3/12 - 4/12 3 3/4" 4 1/4" 5 3/4" 3 1/2" 4" 5 1/2" 3" 3 1/2" 5"
4/12 & steeper 5" 5 1/2" 7 1/2" 4" 4 1/2" 6 1/2" 3 1/2" 4" 5 1/2"

Exposure specifications for wood shakes are detailed at WOOD ROOF SHAKES INSTALLATION.

Wood Roofing Shingle Specifications & How are Wood Shingles Nailed onto a Roof?

Wood shingle application (C) Carson Dunlop AssociatesWood roof shingles are typically 16", 18" or 24" in length and up to 13" in width (but limited to 8" in width in some building codes).

Carson Dunlop's sketch (left) illustrates the typical wood roof shingle application pattern.

The shingles are 4/10" to 1/2" in thickness, and wood shingles are installed with a 5" exposure (16" shingle length), 5 1/2" exposure (18" shingle length), or 7 1/2" exposure (24" wood shingle length).

The typical life of a wood shingle roof is 30-40 years, but life expectancy varies considerably depending on how the shingles were installed as well as on the pitch of the roof (its slope), and its sun and weather exposure. (Too much sun dries out the shingles leading to splitting, and too much shade may keep the shingles too damp, leading to rot.)

Shingle quality and shingle treatments (for example with preservatives or with protection against photoxidation) are important life factors as well. Wood shingles are installed on roofs with a slope of 6" in 12" for best performance but may be on a slope as low as 4/12.

Wood shingle nails need to be long enough to penetrate 1/2" (3/4" for the UBC) into the roof wood decking or nailing boards. The diamond-shaped nail tip itself has no holding power, just the roofing nail shank. So if you see shingle nails protruding through a plywood roof deck, that is not an error.

Nail specifications for wood shingles may vary by wood species; using western red cedar as an example, nails are to be corrosion resistant hot dipped galvanized, stainless steel, aluminum, or copper. In dry climates, good quality electrogalvanized staples, conforming to ASTM A641, are satisfactory according to the Cedar Shake and Shingle Bureau, but from our field experience we prefer nails.

Do not use blued steel or copper fasteners with cedar shakes or cedar shingles.

Wood shingle nailing pattern: in most applications only two nails are used per shingle, in order to permit movement without splitting as the shingle expands and contracts during changes in its moisture level. Keep nails about 3/4" to 1" (1" is for the U.B. Code), away from the side edges of the shingles and 1 1/2" (2" for UBC) above the butt line of the following course.

According to the Cedar Shake and Shingle Bureau, fasteners should be driven flush with the shake or shingle top surface, but no so deeply that the head crushes the wood.

For added details about proper wood shingle or wood shake roof installation, perhaps the most authoritative source of wood shingle and wood shake information is from the Western Red Cedar Shingle & Shake Bureau (now the Cedar and Shake Shingle Bureau, since not only western red cedar is used for roof shingles).

Eaves Flashing Details for Wood Shingle & Shake Roofs

As stated in Best Practices Guide to Residential Construction (printed text) chapter BEST ROOFING PRACTICES:

Apply eaves flashing to either spaced or solid sheathing in regions with an average daily temperature of less than 25°F (under the IRC) or in other areas prone to ice and snow buildup.

The eaves flashing should extend up the roof to a point 24 inches inside the building. Where eaves flashing is required with spaced sheathing, install solid sheathing along the bottom section of the roof to support the eaves flashing.

Wood Shingle & Shake Nailing Guidelines

Continuing from from Best Practices Guide to Residential Construction:

Fastener Specifications for Wood Shingle & Shake Roofs: Nails, Staples

Table 2-15: Wood shingle or shake nails (C) J Wiley, S Bliss

All nails should be either stainless steel (type 304 or 316), hot-dipped galvanized, or aluminum. Staples should be either stainless steel or aluminum. Galvanized staples will not last the life of the roof.

Table at left - Best Practices Guide to Residential Construction

Treated wood roof shingles may require stainless steel or other special fasteners. Consult with the treatment company for recommendations. Stainless steel is also the first choice in coastal environments.

  • Nails used with wood shingles or shakes should be box type and penetrate the sheathing by 3/4 inch (Table 2-15 above/left)

    [Click any table or image to for a larger, more detailed version.]
  • Staples used on wood shingles or shakes should have crowns between 7/16 and 3/4 inch wide and penetrate the sheathing by 3/4 inch.
  • Drive wood shingle nails flush. Do not drive nail heads or staple crowns below the surface of the shingle. Underdriving or overdriving weakens the shingle attachment.
  • Placement of wood shingle nails. Each shake or shingle should receive only two nails. Place one fastener 3/4 inch in from each edge and about 1 1/2 inches above the exposure line (Figure 2-50 below).
Figure 2-50: wood shingle nailing pattern (C) J Wiley, S Bliss

Wood Shingle Installation Specifications

Whether installed over solid sheathing or spaced sheathing, follow these guidelines:

  • For the starter course, double or triple the shingles in the first row.
  • Each shingle gets two nails about 3/4 -inch in from each end, and 1 1/2 inches above the butt line of the overlaying shingle.
  • The first course should overhang the fascia by 1 1/2 inches. All courses should overhang the rake by about 1 inch.
  • Leave a gap of 1//4 to 38 inch between adjacent shingles for expansion when wet.
  • Offset joints in successive courses by at least 1 1/2 inches (Figure 2-50 shown just above). Also, no more than 10% of joints should line up with joints in alternate courses (two courses away).
  • Flat-grain shingles wider than 8 inches should be split into two shingles before installing.
  • Treat knots, similar defects, and centerline of heart as if they were joints between shingles, and locate the defect 1 1/2 inches from joints in the row above or below.

Wood Shake Roof Installation Specifications: Felt Interlay or Felt Underlayment

Details for installing wood shake roofs are at WOOD ROOF SHAKES INSTALLATION.

Details about felt underlayment requirements and wood shingle or shake course interlayment are provided at WOOD ROOF SHEATHING, UNDERLAYMENT.

- Adapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:

Side-lap Wood Shingle Roofs

See "Fabricating and Installing Side-Lap Roof Shingles in Eastern Pennsylvania", James Houston & John N. Fugelso.
Quoting from that article:

In order to restore some of Pennsylvania’s historic buildings, the authors are recovering a lost trade practice.
Over the past decade of working on side-lap-shingle roofs, the authors have observed many earlier attempts by others to make the process of replicating these roofs faster and less expensive. These attempts have included substituting materials, sawing and planing shingles rather than riving them to speed the manufacturing process, and adding other materials between courses to reinforce the roofing system. All of these attempts have saved money and time in the short term but have failed to perform long enough to realize the savings.

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