I live in Northern Cal also--Sonoma side. I have a sand side of the pen, which stays drier, and the straw side, which gets the rain from the wind coming up the hill. We just took off the plastic top and added a second run, and both will now have a composition roof. I can't let the chickens roam as we have too many predators. Fortunately, we don't have below-freezing temperatures, but we have plenty of very hot days.
I always thought lime was a bad thing to get on yourself? I have a fly trap hung nearby, which takes care of those pests, and I clean their run and coop every day, so we don't have any trouble with smell.
Maybe I can get the local landscaping material company to make a mix of sand, peat and dirt, but I don't know what percentages I should ask for; one-third each?