Roof maintenance/repair
 

After recently finding a lot of fallen moss on my deck, I headed to my roof to attack the infestation with a push broom and screwdriver. I've got it mostly cleaned up, and I'll hit it with a bleach solution soon, but I found a patch on my roof where most of the rock granules have been washed away.

The upper roof gutters drain down to the lower roof as pictured, and this has washed away most of the rock granules from the shingles. The roof is no more than 18 years old. Do I need to replace the section pictured here? Should I extend the gutter drain to empty directly into the lower gutter instead of dumping onto the roof below?

http://i7.photobucket.com/albums/y26...m/KIMG0105.jpg

http://i7.photobucket.com/albums/y26...m/KIMG0106.jpg

And lastly, I found a hole in the gasket of a vent. Does this need to be sealed? If so, do I just use roofers tar, or is there a better product?

http://i7.photobucket.com/albums/y26...m/KIMG0108.jpg

looks like a cracked shingle or two there, you still have the top half of the shingle below keeping you dry, plus the felt paper underneath, but you might want to fix those. The granules wearing away is not a big deal. Don't see any curling tabs, which is a good sign. Looks like a 20 year shingle, but can't tell from here. It's not uncommon to get 25 years or better up here in the PNW.
The vent stack boot is shot and should be replaced, but you can buy some time. Slather some Henry's roofing mastic on it, wrap it with webbing, yellow self sticking drywall mesh tape will work, then slather on more Henry's.
You can get a roll of zink in the roofing dept, it helps slow the moss down. Typically it's installed before the ridge cap goes on, but you can figure something out :)

I'm not sure about replacing it. I would imagine if there is no water damage, you should be fine. I would certainly replaced any rusty flashing though. You should definitely extend the drain pipe further down before it causes major problems.

If you haven't gotten any answers, next time I see a friend of mine who is a roofer, I will ask him his opinion.

EDIT: I guess Jasen beat me to it. :)

The drain pipe that dumps on to a lower part of the roof is not normal and now we know why.

You have to seal around that pipe, don't use roofing tar it will crack and seperate after 6 months if not sooner. Best thing for that vent boot is pull it up and stick a new on on there. Looks like its only got a few years before it rusts through. They are not very expensive.
Patch it with anything before it rains again, tie a rag around it or something at the very least.

With out a good roof nothing else you do to fix or improve your house matters much.