what is wrong with this valley?

In this situation he should have measured the roof than divided that total to lay courses as close to 10" exposure as possible. Looks like he may have got lucky and wound up with an acceptable exposure by accident. Will you be tearing off his entire job or working with what you got?

"Copperman" and "Old School" are correct. The whole left side looks like the addition? With the felt installed this way...It will weather at a fast rate over time, will crack and finially split. If there is a seam on seam or close to it, it will leak on the bare plywood...or in another case I experience!!!!

A 50sq shake job about 7 yrs old was installed the same way.....with "spaced" sheeting. With seam on seam in many places on this roof, the felt was cracked wide open....dumping water through the gap in the spaced sheeting. Customer did not want to replace the roof and wanted the quickest and most inexpensive solution, so used 5 bundles of 8 x 12 step for all the cracks I could find.

---I didn't take any pics of the finished repair. Basically I cut the valley pieces as normal and installed them piecing in the gaps. ---The left side felt is indeed wrong and that was the addition tied into the old roof (right side) at the valley. Since it was 12/12 I didn't deal with anything except the valley. I did use some 16 inch shingles to fill some holes. I use them instead of tin shingles for crack over crack repairs because they are cheaper. Lanny