I am getting ready to install a wood fence. My problem is I have soil that is mostly clay. What is the best method to install posts in poor draining clay, giving me the best longevity?
When I redid my fence 2 years ago, I went with PostMaster metal posts (http://contractors.masterhalco.com/Contract.nsf/woodpostmaster). They weren't substantially more than a good PT post at Home Depot. You can also easily wrap them with a picket so you don't see metal.
I dug the holes about 30" deep, then just drove the posts into the dirt til they were the right height - much easier than cutting them. You could put a couple inches of pea gravel in the hole, but I just did concrete. My hope is that even if I have to rebuild the fence in 20 years, I'll never have to replace the posts.
I have installed a few posts over the years. I am currently using this method. All my Corner, Gate, H bracing, posts. I applied Drive way sealant on them. 4 feet from bottom. I have 1 foot above ground. 3 feet in the ground. Now... My understanding is todays salt pressure treated wood has a negative chemical reaction to todays concrete. So you get post breaking at the soil/grade level. So my answer is to seal the bottom 4 foot of your posts, with driveway sealant. Put a little gravel at the base of your hole. Add your concrete, and fill to a cone shape above ground. Any input is appreciated. Its a new method for me.