1. Roof deck may be spaced or solid sheathing.

2. Fill in between existing spaced sheathing boards is recommended but not required for class “A” roof systems.

3. Shake installation may not be applied directly over rigid insulation board.

4. Shakes may be installed over one composition or wood shingle roof if the roof is in reasonable condition.

5. Shake recovers over shakes or laminated composition shingles are not allowed.

1. All field felt shall be a minimum 18” wide 30# felt interlayment installed to the desired shake exposure, not to exceed a nominal 10” exposure. 102” exposure over 10 courses shall be accepted as maximum tolerance.

2. No additional underlayment is required when roofing over existing composition or wood shingles.

3. All sheet metal valleys shall have a 36” wide 30# felt underlayment.

4. Slopes less than 4/12 require additional underlayment. The IRCC recommends a mineral surfaced cap sheet.

5. Application of wood shakes on slopes under 3/12 should be over an impermeable membrane where the shakes are installed for aesthetic purposes only.

6. A class “A” shake system requires a mineral surfaced cap sheet underlayment with class “B” shakes.

1. Nails shall be EG type, box nails, long enough to penetrate 3/4” into or through the sheathing board.

2. Staples shall be galvanized type, 7/16” crown minimum, long enough to penetrate 3/4” into or through the sheathing board.

3. Shorter fasteners are acceptable for use at overhangs and eaves to minimize penetration of the visible underside.

4. Fasteners shall be located so as to penetrate the underlying shake and be covered by the overlaying shake. Two fasteners per shake are required.

1. Starter may be field shakes or wood shingles.

2. Starter should be fastened in the same manner as field shingles.

E. FIELD SHAKES:

1. No felt shall be exposed between the open keyways.

2. Keyway spacing shall be 5/8” maximum.

3. Shake keyways in alternate courses shall offset 1 1/2” minimum.

4. Shakes shall have a minimum width of 4”.

F. VALLEYS:

1. 28 gauge, 24” wide, W type metal valley may be used. The shakes should overlap a minimum of 6” on each flange.

2. Closed valleys may be installed over metal valley but is not recommended.

Typical shingling to a metal valley

1. May be reused if in serviceable condition. When roofing over an existing roof, the base flange and step shingles should be lifted and installed into the new roof

2. If counter flashing is replaced, it may be fastened to the chimney with concrete nails and sealed with a good exterior caulk.

1. May be reused if in serviceable condition. When roofing over an existing roof, flashings should be lifted and installed with the new shingles.

2. Plumbing pipes may be sealed to the flashing with flashing tape, rubber collar, or plastic cement.

3. Painting of flashing to blend with the roofing is desirable but not required.

4. Exposed galvanized fasteners on base flashing is acceptable.

1. Edge metal is required to cover exposed edges of plywood.

2. Edge metal is not required but is desirable to cover exposed edges of the original roof when overlaying an existing roof.

3. Painting of edge metal is not required.

4. When flashing against a vertical side wall:

a. New flashings may be installed if feasible. If new flashings are installed on the exterior of the wall, the flashing should be counter flashed with wood or metal sealed to the wall with a good exterior caulk.

b. The old flashings may be reused if in serviceable condition. The flashings should be lifted and installed with the new shingles.

1. Ridge should be installed with one galvanized nail on each side penetrating into the sheathing at least 3/4”. Exposed nailing is acceptable.

2. Spacing of ridge shingles shall match that of the field.

K. BUILDING DEPARTMENT INSPECTIONS:

1. Pre-inspection of roof overlays should be required.

2 In-progress inspections should include spot checks of decking, plywood nailing, shingle application, and flashing installation.

3. Final inspections should be done from the ground if inspectors do not provide their own ladder.