What steps should I take to roof a valley with a California cut on both sides?

What are the steps to roofing a valley in which I’m creating a California cut on both sides of the roof? -- Maryville, Tenn.

There may be several ways to create a California cut in your roof valley, but this is the method I have always seen used:

1. Lay the roofing felt and install valley flashing as you normally would. If you live in a colder region, you should invest in an ice and water barrier for the valley.
2. Install the shingle rows on the roof slope, starting with the lowest pitch first. Take each row through the valley onto the adjoining roof section about 12 to 18 inches. If the two roof sections have the same pitch, start with the slope at the lowest height.
3. When the first section is complete, fix a line of vertical shingles up the valley with the exposure edge about two inches back from the line on the second section's side.
4. Place the shingle rows along the second section, allowing each row to cover the vertical shingles up to their exposed edges.

When you have completed the second slope, the valley has a California cut. The name is a little misleading, as there are actually none of the cuts you would encounter with a conventional valley installation.

A California cut is considered to be an easier method for shingling a roof valley than the more traditional valley style, but for warranty reasons it's normally only used in warm, dry regions of the country. Since you're located in Tennessee where it's humid, you may want to check with your shingle manufacturer to ensure they will still warranty their product, if you use a California cut in the valleys.