Morning bud,
A wood rail fence can be a thing of beauty. I was raised fencing by a fenceman. Dad used to say what he liked best about fencing was you could drive up on a site and it wouldn't be anything. And when you were done it was a thing of beauty. Not many jobs could give you so much instant gratification for a job well done.
Your posts, I'd go steel. Second choice would be four by six cedar, third choice four by four cedar. Last choice short of suicide would be landscape timbers. There's a reason they're so cheap.
I'd want to go six foot centers on post spacing. Eight feet will work but six is much better over the long haul.
All of my post holes are one foot diameter and three feet deep or to rock, period, end of story, enough of that. They are full of concrete. That's two and a half sacks of sacrete per post if you're using eighty pound sacrete, which is fine btw. Maximizer is easier work with and so far has worked just as well.
Another thing I do is I clean the hole. Yup, I use a power post hole digger and then when I come back with manual post hole diggers and I clean the hole as well as I can.
You see I figured out awhile what causes the dips and sways in fences. It happens when that loose dirt eventually compacts. The concrete and post sags or dips accordingly.
I had a bud the other day ask me how come all my fences are straight six, eight, ten, years later while everyone elses are wavey. I told him I was just lucky. The simple truth is that little bit of extra time cleaning the hole and mixing the extra concrete, no, I don't pour sacrete in the hole and then come back watering it. BTW I like it when my competition does. It's so much easier removing the old post when doing a repair.
Your rails should be sixteen feet long if you're going eight foot centers. Ideally they would be twenty fours if you're going eights or sixes.
The reason for this is you want to stagger your joints as much as possible. This makes the fence much stronger. To place your rail joints at each post would be like bricking a wall and not staggering your joints.
Another thing that I've found is important is to have a substantial top plate. Let's say you're using four by six posts and two by six rails. On top of your posts you would place a two by six so that it would give your two by four top rail the profile of a two by six. You also want the joints of your top plate to be as far as possible apart and never ever anywhere but centered over a post.
What this does is give your fence some lateral strength so that it stays straight. I build fancy <A target="_blank" HREF=http://photos.yahoo.com/bc/wroughtnharv/lst?&.dir=/Wood+fences+and+gates&.src=ph&.begin=9999&.view=t&.order=&.done=http%3a//photos.yahoo.com/bc/wroughtnharv/lst%3f%26.dir=/Wood%2bfences%2band%2bgates%26.src=ph%26.view=t>wood</A> fences. Some of them cost over a hundred dollars a lineal foot. But even my fifty dollar a lineal foot fence has a two by eight top cap. This allows me to drive by that fence many years later and not have it waving at me like we're family.
If you're going to use wolminized or treated materials keep in mind that the worst thing you can do is get wet material. You can never tell which direction it's gonna go when it dries. So always pick through and find the lightest boards. Chances are they are the ones that are in their final state.
Those two dollar and twenty nine cent landscape timbers are pure junk. They twist and bend as they dry out. They rot. And they have their knots in all the wrong places.
If you're doing this fence yourself as you can then I'd go stainless screws. If you're using a nail gun you can buy stainless nails for it. They're not cheap. But galvanized will react to cedar and the minerals in treated lumber.
There are few things more beautiful than a well built fence. But a fence is like the frame on a picture. A good one just blends in and isn't really noticed but by the discerning. But a bad one is so obvious that the quality of the picture is hard to appreciate.
