Ventilation requirements for wood shake roof shingles?

ALL KNOWLEDGEABLE INSPECTORS,

What are the ventilation requirements for wood shake roof shingles? House has 12/12 pitch with only gable vents installed.
We don’t come across wood roofs very often.

Thanks in advance for your help.

John,
almost every install best practice imaginable
http://www.cedarbureau.org/installation-and-maintenance/roof-manual/

Best practice is wood shingles with a breathable underlay on spaced sheathing with continuous soffit and ridge venting. Basically you want as much airflow as possible to allow for fast drying.

Solid sheathing and gable vents work, but would dry slower, which would affect the lifespan of the roof.

No underlay at all with wood shingles. CSSB (Barry’s post). Lee’s right about airflow. Fast drying is more important than preventing intrusion. Preventing intrusion is done through maintaining proper exposure and sidelap.

Mastering Roof Inspections: Wood Shakes and Shingles, Part 1
Mastering Roof Inspections: Wood Shakes and Shingles, Part 2
Mastering Roof Inspections: Wood Shakes and Shingles, Part 3
Mastering Roof Inspections: Wood Shakes and Shingles, Part 4
Mastering Roof Inspections: Wood Shakes and Shingles, Part 5
Mastering Roof Inspections: Wood Shakes and Shingles, Part 6
Mastering Roof Inspections: Wood Shakes and Shingles, Part 7

From Mastering Roof Inspections - InterNACHI http://www.nachi.org/mastering-roof-inspections.htm#ixzz2B68RC85s