Jimmie's Guide to Building or Replacing Fences

Tools.
 Shown here are the tools needed to dig the post holes, as well as to add the (optional) animal control "foundation". There's the post-hole digger, and the slender "hole shot" shovel is good for enlarging one or more sides of the post hole, and is also useful for cutting into the soil for placement of cinder slabs/bricks
 The long metal rod is sometimes called a "digging bar" or "wrecking bar". It is priceless! I have used it many times for prying up dead shrubs or breaking up rocks. Here, it can be used if you encounter some hard soil while digging the post holes.
 And the saw? It's for cutting away certain parts of the old fence if you are replacing an existing fence.

And here are the tools necessary for assembling the fence itself. The crowbar and the yellow pry bar are useful for disassembling the existing fence. The orange level helps you set the posts upright and the horizontal support members "horizontal". And the drill and bits? That's explained below. The needle nose pliers are for pulling the staples out of the old fence slats if you want to save a few of the slats. Why do that? Because cedar fence slats, if pressure washed, make great "reclaimed" wood for projects.

Fasteners.
 And here are the fasteners and other hardware that are associated with fence building.

The roofing nails are for attaching the 2x4 fence brackets (shown at the bottom) to the posts and for securing the horizontal 2x4 pieces in the brackets.

The longer "Split-proof siding nails" are 16d, and are used mainly for attaching the top decorative piece and/or any nailing of larger pieces of wood. "16d" essentially means a nail that is 3 1/2 inches long.
In less salty climates, you can use the galvanized 16d finish nails shown on the lower left. Why "finish" nails instead of nails with heads on them? They just look better. I have always used these types of nails for decks, wooden walkways, and fences when I lived in Texas.

The "Wood Siding Nail", 1 3/4 in, is for nailing the fence slats. (unless, of course, you have a nail/staple gun).

The metal items on the bottom are the metal brackets for the horizontal support boards.

Wood.
 The picture on the right shows a completed section of my new fence, to give you an idea of which type of fence this article is about. The fence slats are three inches apart, and alternate on each side. This is the type of fence type used in windy areas, since the air can flow relatively easily between the slats. It also looks good from both sides.
 The usual fence has all the slats on one side, perhaps an inch or so apart. It's a bit easier to build, although it looks better on the side with the slats.

The posts. If you are replacing an existing fence, you might be able to use the existing posts. Pressure treated "ground contact" wood will last a long time. This is usually the wood with the rows of slots in the sides (see the images below). Dig the dirt away from the existing posts and check if the wood is in good shape. If the posts are in good shape and feel firm if you push against them, they can indeed be used.
If not, get 4x4 pressure treated posts, 8 feet in length. (You will cut the tops off for a 5 or 6 foot high fence). If you are building an 8 foot high fence, get 10 foot posts.

The horizontal cross pieces. These are 8 foot 2x4 pressure treated wood. Get the "ground contact" rated even though they're not going into the ground. They last much longer.
 Quantity: If you use 3 horizontal cross pieces per section (discussed below), you will need 4 of the 8 foot 2x4s per section. This includes the decorative top piece.

The fence slats. Get 6 foot or 8 foot as appropriate. Cedar is by far the best wood. It will promptly weather to a grey, but will last for years. Cedar is the standard for coastal areas. I had a fence built when I lived in Texas. The fence slats were "treated" wood, and they promptly warped and split after a few months.
 Quantity: If you use fence slats on both sides like this, you'll need about 16 slats per 6 foot section, or about 22 slats per 8 foot section.

Spacing (So you can calculate how many posts you'll need).
 Most fences are 8 feet "on center". The posts are 7 - 8 feet apart. But there are several reasons for using 6 foot spacing instead:

If you live in an area with occasional strong winds, the fence will be considerably stronger. You could use 5x5 posts and keep an 8 foot spacing, but 5x5 posts are very heavy, and would require you to enlarge the holes dug by a typical post hole digger. I used a 6 foot spacing on the "windward" side of my yard, and this resulted in 5 posts in the 80 foot span instead of the original 4 posts. That's about 25% stronger overall.

The fence is less likely to sag as time passes.

If you have an existing fence with 8 foot spacing, and the posts are in bad shape, if you change to 6 foot spacing for your replacement fence, you eliminate the (serious) problem of having to dig up the existing posts and trying to remove the concrete. The new posts won't co-incide with the location of the existing posts - you can simply cut off the existing posts at ground level. (But don't cut 'em just yet; they can help you line up the new posts.)

The Posts (New Post Scenario)

1 Some tips on digging the hole.
 For starters, sharpen your post-hole digger!! No, really!
 They're usually blunt from the factory, and sharpening them makes them much easier to dig with. ("Work smarter, not harder".) Just taper one side with a long flat file. The same applies, by the way, to your garden hoe! It cuts the soil and dislodges weeds much easier. Buy a 12 inch file for this purpose. A bigger file allows you to take longer strokes and remove material faster.

2 Mark the sides of your post-hole digger. Just 2 and 3 feet marks should suffice. This helps you determine how deep you have gotten - and thus keep your spirits up! (Some fancier ones have depth marks on the side already.)
 How deep to dig, you ask. Most references suggest 1/3 to 1/2 of the height of the post above ground. The type of soil makes a BIG difference. Sandy soil won't offer much support. But clay coils are so firm that the 1/3 figure is plenty. This would be 2 feet for a 6 foot fence or about 2 3/4 feet for an 8 foot fence. More on this later. I was surprised to find that my existing fence was 5 feet high. So 2 is plenty.
 Translation: You dig as deep as the soil or rocks will LET you dig!

3 If you encounter harder soil or perhaps rocks, use the digging bar.

4 Stretch a line from the end posts, close to the ground. This will help you line up the holes, so the bottoms of all your posts will line up.
 Also stretch a line at the top of the planned fence height. The two lines will help greatly in keeping the bottoms and the tops of the posts in a straight lines. These are your "Calibration Lines"
 I am using the end posts from the original fence, so I attached the line to the posts. You can use a staked pole or 2x4 if you are building a completely new fence.

6 I used the original fence slats to temporarily secure the posts. The upper slat shown here is attached to the existing post on the left and the new post on the right. Start by "tacking" the slat to the existing post (i.e., don't drive the nails in fully). Then use a level to get the new post "plumb" (upright) in the left or right direction - parallel to the fence's length - and then tack the slat to the new post.
 Now tack another slat to the post. That's the lower one in this picture. The other end of this slat is clamped to a stake in the ground, as discussed in the next picture.

7 So the lower fence slat secures the post in the other direction (toward or away from the yard). Just move the post until it is just touching your "calibration strings" Then tighten a C clamp to secure the loose end of the slat to a stake in the ground. Why clamped instead of just nailed? Because it's easier to nudge the post a bit and then tighten the "C" clamp on the stake.

8 Here's two more posts. These posts are secured to one stake in the ground. (I just broke off a piece of a slat using a chisel to make these stakes.) Use a level to get the posts plumb in the direction parallel to the new fence's length (to the right and left in this image). Straighten one of the posts and then use a C clamp to secure its temporary fence slat to the stake. Then straighten the other post and then tighten its C clamp to the stake.
 That's my blueberry plants in the background. All the strings and slender posts are holding up the bird netting!

9 Here's a view of three of the posts all secured and ready for the concrete. In this picture, the post in the foreground and the post in the middle are just tacked to an existing post rather than to a stake in the ground. Use a level on each post for this direction.
 For the perpendicular direction (toward or away from the yard), I used the calibration string.
 What's up with all the upright rectangular cinder blocks in the pictures? They were used to to keep the rabbits out of my blueberries and strawberries. I will talk more on this in subsequent panels.

10 Adding concrete:
 So here's Jimmie's method:

Start by pouring some dry concrete into the hole.

Have a garden hose and sprayer ready and just squirt a small amount of water into the hole. Tamp the moist concrete down with a small board - I used a 1x2 about 4 feet long.

Continue to add dry concrete and a small amount of water and tamp. You are adding only about 1 - 2 inches of concrete each time. If you get the mixture too watery, just pour a bit more dry concrete. Tamp some more. If too dry, just squirt in some more water. You don't want the mix to be as wet as you might if you were mixing concrete to pour out of a wheelbarrow or bucket. The mix should be just moist.

In the adjoining image, I have worked my way up to almost the top. Note that the mix on the left side of the post is a bit too dry - you can see some dry concrete. So spritz in a bit more water. The mix on the bottom is slightly too moist - some water has pooled up. So just sprinkle in a bit more dry concrete. Tamp some more.

Make sure the post has not moved! Using this process, once you get about halfway up the hole depth, you won't be able to move the post!

Wear safety goggles! If you get too much water, the mix will splash out of the hole, and the manufacturer indicates on the bag that concrete mixture is apparently not the safest thing around!

11 One more time. Here I am at the top of the hole. I add another layer of dry concrete.

12 Then I add just enough water to make the mix have the consistency of thick biscuit dough.

13 Finally I add some more dry concrete and then add a bit more water than usual, so that I can smooth out the top with a wide putty knife. The concrete is tapered - highest next to the post and lowest at the edges.
 This allows rain to flow away from the post. Above all, there is no soil up against the buried part of the post. Notice that the soil level is higher behind the post (where the river rocks are). I will fill that area back in with gravel, not soil. Thus rainwater can percolate through the gravel to the lower area on the right.
 The metal piece is one of the horizontal support holders - to be discussed in a bit.

14 So here's all the posts nicely lined up, thanks to the two Calibration Strings. Now it's time to cut the tops of all the posts. If you thought "well, I'll just dig each of the holes such that the tops of the posts all line up without needing to be cut", by now you have seen the reality of post hole digging!
 Mark the posts using the top calibration string as a guide, assuming you have tied the top string at the height you want the fence to be. I used the top of the two end posts of my original fence as a reference (picture #9). If you have a square (not shown in the "Tools" above), make a mark on each side of the post to help guide the saw.
 HINT: Get some white pencils (from the school and office section of the grocery store). You can't see regular black pencil marks on all this brown wood!
 Use a reciprocating straight saw if you have one. Otherwise, use a portable saw, making a cut on each side. The combined cuts should be sufficient to cut the top off. Careful! The saw will sling the top off when the saw reaches the other side! Mine flew out in the yard about 10 feet.
 You can certainly use a hand saw, but it's a bit dificult to use, and it's also hard to keep it straight.

The Posts (Use Existing Posts Scenario)

Here's some information on building a new fence but using the existing posts.

 15 TIP: The old horizontal crosspieces are devilishly HARD to remove from the existing posts. You can't pry the ends loose because the posts won't move. So, simply cut the middle of the old crosspiece. I used a coarse bow saw, which cuts easily through the wood. Once cut, you can simply lift each section and the nails will come loose.

16 Once you have removed the existing horizontal support pieces, you want to clean up the original attaching spots. This one is at the top of the post. (If you live on the coast like I do, the area will be covered in spider webs!)

17 So I have wire brushed the area and sprayed with a wood preservative. (See #21 for name)

18 On the bottom of the post, I have removed the soil down to the existing concrete, which or some reason was unusually flat.

19 So I wire brushed the area and sprayed with the preservative. I used the blue "painter's tape" to keep the spray off the new fence slat. (I didn't tend to the bottom of the posts until I finished the fence!)

20 I replaced the soil with "3/4 inch drain rock", but any kind or gravel or pea pebbles will be fine. Notice that I have also dug out the area to the left of the post, which is lower, and filled it with the gravel. This provides drainage, since it is lower than the post. If I had simply filled the cavity around the post with gravel, the surrounding soil would trap water and never drain.
 If you have level soil, you may be forced to add concrete and taper it, as discussed above.

21 And here's the preservative compound I used.

The Horizontal Supports (Straight-Top fence)

22 Here I am adding the metal brackets for the bottom 2x4 support boards. I have moved the bottom "Calibration String" to line up with the desired height of the bottom of these boards.
 A note: When I built the fence for this side of the yard, I completed the fence first and then added my "animal control" blocks after it was finished. If you are not concerned about intruding rabbits getting in or your pets getting out, you can ignore all this business of "animal control".

23 Now I am at the top side of the posts, adding the metal brackets for the top crosspiece (support) boards. Take a piece of a 2x4 and use it to judge where to add the brackets. The top of the 2x4 needs to be even with the top of the post. Mark the bottom of the bracket.
 This is an important step. If the support board is lower than the post top, the "decorative" 2x4 - when laid sideways on the top - will bend when you nail it. This will make the fence look like it sagged. If you do end up with a support board lower than the post top, just nail the decorative piece to the post, but don't nail along the length of the decorative piece for 3 or 4 feet. Or use some kind of shim underneath it.

24 Back to the bottom again. I have already placed all the bottom boards into their brackets. Now I want to add a second horizontal crosspiece right on top of the first one. This helps create a barrier to help in animal control. If you aren't interested in animal control, you don't need a second board.
 However the second board also adds more support and will keep the fence from sagging after a year or two, especially if you have 8 foot spacing between posts. In this case, it would be well to add the extra board midway between the top and bottom crosspieces.
 In any case, if you are adding a second bottom board, use a paint stick or something about 1/4 inch thick to space the second bracket a bit above the top of the first board. This helps allow the adjacent surfaces of the boards to dry out after rains.

25 Adding a nail to secure the crosspiece to the bracket.
 TIP: Always drill a pilot hole when nailing near the end of a piece of wood. Use a bit just slightly thinner than the nail itself. This keeps the wood from splitting and makes for a MUCH stronger joint.
 NOTE: if the support board edge is lower than the post top, you can line it up by raising the support board a bit before you drill the nail holes. If the edge is higher than the top of the post, just bend the bottom part of the bracket. "How'd the edge end up lower or higher when I marked the bracket position in Step 23??" That's because this sort of lumber has variations in width. Some "2x4" pieces are wider than others.
 The stain on the new post is due to my application of the preservative spray on the raw wood that has been exposed when cutting the top off. This helps keep the top of the post in good shape.

26 Here's a shot of the corner of the new fence, with all the horizontal crosspieces in place. (This is the South side of my yard.) I have added a block retaining wall/animal keepout in this area due to a sharp drop-off in the grade.
  As noted, I used the existing corner post, which was intact, and which was longer due to the drop-off. The existing fence slats are seen on the left also.

27 So here's the South side, ready for the fence slats. For this side, I added the bottom crosspieces first. Then I placed the "animal control" blocks next, bringing them up to almost touching the bottom of the lower crosspiece (two sections are fininished in this pix). On the North side, I decided it might be easier to construct the animal control blocks first - discussed below.

28 On the other end, I build another block wall. You can see the animal control blocks also in the adjacent section. Before installing slats I actually added a third horizontal support in this section, above the two support crosspieces seen here.

The Horizontal Supports (Staggered Top fence)

29 On the North side, I decided to construct the animal control blocks first. They are cinder rectangles, 16 x 8 x 2 inches. I used a level to keep all the top edges straight.
 In this scenario, having done the blocks before the crosspieces, I rested a horizontal crosspiece on two paint sticks - to maintain a gap between the wood and the blocks. Mark the bottom edge on the post for the position of the brackets (Notice my white pencil resting on the wood).
  "But you didn't go up to the edge of the posts with the blocks", you may say. This is because the post concrete is in the way.

30 Here's a pix of the first row of bottom boards. As you see, there is a gap on both sides of the posts, since I couldn't bury the cinder blocks due to the post concrete. Also, in most cases, the 16 inch long blocks would not fit. See picture #20 for what the completed post area will eventually look like.
 Please see also sections 1A through 4A below, under "Some Additional Tips", for a way to handle the animal control blocks when you have a fence with all the slats closely placed on one side only.

31 As shown in picture #23 above, I use a 2x4 piece to mark the position of the bracket. This is the "Staggered Top" type, so I do this procedure on the side where the crosspiece is even with the top of the post.

32 For the opposite side of the crosspiece, I support the board with a 2x4 scrap secured with a C-clamp. The scrap piece of the old fence slats is on the other side of the post - to keep the C-clamp from scarring the post. Place a level on the board and tighten the C-clamp when you determine it is level.
 Normally, you would eliminate all this C-clamp business, and simply mark the bottom of the wood and place a bracket there to hold the wood. But I ran out of brackets!! So I am "toe-nailing" the wood to the post. Note the nail placed in the pre-drilled pilot hole, ready to be driven into the post. As noted before, pre-drilling near the edge of any piece of wood makes for a much stronger joint. This applies expecially to toe-nailing.

33 So I am now ready for fence slats on this Staggered top fence. Note that there are two bottom crosspieces as well.

Pet Peeve Time:
 34 Remove the green tags! It just makes for a prettier installation. Most contractors leave them on, and they last for years. Show some class. . .

The Fence Slats

35 Place some weight on top of the fence slats you haven't used yet! This is true whether it is sunny or if it rains. Why? See next pix.

36 The slats will bend in the sun or the rain! Actually, if you expect rain, cover all the wood with a tarp! Wet wood is hard to work with!
 For the same reason, stack all your 2x4s (shown in the prior picture). Otherwise they may bend or warp if just strewn around on the ground. It is very important to keep these 2x4 horizontal crosspieces straight. Actually, if you have a chance to pick them out at the time of purchase, sight down each board and reject any that are bent.

37 Slat spacing.
 The original fence slats were about 3 1/2 inches apart. I decided on 3 inches. Find a scrap board or object that is 3 inches wide and simply place it between each slat and the prior one. This is a lot easier than trying to measure between each one. Start with a slat right up next to one of the posts in an given section; leave just a tiny gap for expansion and for better drying after rains.
 As with all home improvement projects, just "tack" the slats in place. That is, don't drive the nails all the way in. Why? Just in case something is wrong; you can just pull the nails right back out. I've had to do this MANY times in past projects.
  Put one nail in the top part, near the edge of the slat.

38 For the bottom, notice the nail is on opposite side. This helps prevent warping, since the slats will be exposed to the sun for the first time.

39 Nail the slats on one side first. As mentioned above, start with one slat almost next to a pole. In this picture, I started on the right side of this section, so the first slat is not seen.
 Do all the slats on one side first. Usually you will end up with a gap between the last slat and the next post. So now go to the other side and start that side with a slat next to the post. This will fill the gap. For the second slat on the other side, placing it 3 inches from the first one may not result in the desired location. Consider the gap between the leftmost two slats on this side. You want the second slat on the opposite side to be in the center of that gap. Place that second slat accordingly, even if that makes it closer than 3 inches from the first one. Then you can use the 3 inch "guage" to place all the remaining slats on the opposite side.

40 Every home improvement project is a learning experience! I placed all the fence slats on the South side of the yard by holding them up so that their tops were even with the top horizontal crosspiece. So when I got to the North side I said "Duh!"
 Tack an old slat or something on top to help you align the top of the slats with the top of the horizontal support board. Or simply put the top "decorative" 2x4 on first, before you install the slats! This way you can just shove the fence slats up against either of these boards.

41 So here I am, ready to place the decorative top piece on top of all this. (Of course, as discussed in the prior panel, just put the top piece on first, before the fence slats!) The "decorative top piece" is simply another 8 foot 2x4 placed on its side.

42 One more picture showing how straight your new fence can be. Your Calibration Strings will have. paid off.
 But note that some warping has already ocurred with the fence slats. Some of them have pulled away a bit from the horizontal support piece. Thus, finish adding the additional nails when you have done several sections, or have finished one side of the yard. You want two nails/staples on the top of each slat and two on the bottom. I actually used four on the bottom, two sets for each of the pair of bottom support crosspieces. This is important if there is bright sun and especially if rain is expected.

43 The top decorative piece:
 Take this opportunity to do it different than almost all fence installers! in every fence I have seen, the top pieces butt up to each other right on top of the fence posts. This makes the junction on the posts weak and prone to give way in high winds! Instead, place the top piece over the post, allowing the butt joints to be elsewhere.

44 Here's the butt joint somewhere in the middle of a fence section. This technique is similiar to staggering bricks or blocks so that each brick/block rests on the junction of the bricks/blocks below them.

45 Back on the side with the Staggered Top. I show the lower decorative board secured to the post with "toe-nailing". The two nails whose heads are slanted are driven through pre-drilled holes. Use a round punch or something similiar to drive them in so that the nail head is just even with the surface.
 Note that the end of the wood is NOT split! Take a look at your existing deck or porch at the typical edge-of-wood nailing (usually done with a blast from a nail gun). The wood is split in almost all cases. This results in a weaker joint.
 Note the darker stain. I have treated this entire area with a spray of the preservative. This helps seal the cut ends and the wood next to the nail heads.

46 Use 4 or 5 nails at the edges of the top pieces (through pre-drilled holes naturally). Why? This helps prevent the edge from curling up in the summer sun.

YOU'RE FINISHED!

Go pour yourself a cold craft beer in a frosted mug, or a glass of wine.
 If you already have been pouring yourself a beer at some time during the project, go fix the sloppy results!

1A While on the subject of "perimeter" and animal control (keeping the critters out or your pets in), here's how I arranged the cinder blocks on the existing back fence.
 Note that they follow the slope (each block a bit lower than the adjacent one to its left), and are in front of the fence slats.

2A On my new side sections (last year), I placed the cinder blocks in a straight line (that is, not following the slope). The bottom 2x4 support pieces and the slats rest on their tops.

3A But the back fence has all the slats on one side, and the spacing between them is only about 1/4 inch. This is sufficiently close to prevent a chipmunk from squeezing through. So I put the tops of the cinder blocks up close to the 2x4 support pieces, like I had done on the side sections. But this time the blocks are flush with the front of the 2x4 pieces.
 This allows the slats to now extend down below the tops of the cinder blocks. Thus, if the cinder blocks settle a bit and leave a gap between them and the support pieces, the slats will cover the opening.

4A Here is the finished section. On a sloping section, you can either have each slat slightly longer than the adjacent one (so they will follow the slope of the ground), or have some number of slats all even, and then lower the next set of slats, for a staggered look.
  I went with the staggered look, as you can see here.
 NOTE: I used the large paint stick - shown in Section 24 above - as a "spacing tool" to place the fence slats 1/4 inch apart.

Fixing, Straightening, and/or Replacing Posts

NOTE: This adds some additional information on dealing with posts. I already have two sections on posts above:

The Posts - New Post Scenario (images 1 - 14 above)

The Posts - Use Existing Posts Scenario (images 15 - 21 above)

5A This is a shot of the right side of the existing back fence. The camera was held just above the top piece in the foreground, sighting along the top of the fence. The reddish section is the gate (replaced several years ago).
 As you can see, these sections were not at all straight! The post on the left side of the gate (if you were standing in the yard facing the gate) leans out toward the woods; the post on the right side of the gate leans in toward the yard, and the next post (right at the top of the picture) really leans out toward the woods. At the back is a part of the side section of the fence, replaced last year.
 I was going to replace the three leaning posts on the right side and re-use the existing posts for the rest of the back sections. (Last year I re-used the existing posts on the side of the yard that was not directly exposed to the shrieking Pacific winds.) Pressure treated wood is quite long-lasting.
 So I removed the dirt from the lower part of the existing posts, wire brushed them, sprayed them with the preservative, and added concrete, tapered away from the post. In some cases I simply replaced the dirt with small rocks.
 All of this is discussed above (images 18 throught 20).

6A Well, removing existing posts is a job for either more people or more muscle, neither of which I have at hand. Last year I used new posts on the windward side of the yard, but I solved the post removal issue by changing to 6 foot spacing. I could dig new holes between the 8 foot existing posts and simply cut them off. This is discussed above in the "Tools and Materials" section. There is a "Spacing" section under "Wood".
 But here I didn't really want to move the gate and removing the posts on either side of it was "11" on the DIY scale of 1 - 10. So I simply tilted the existing posts to be plumb and straight again (by digging dirt away from one side of the concrete base and placing rocks and new concrete on the other side).
 But the really tilted free standing post was also split throughout. This is the rightmost post in the third picture (of the set of 4 smaller images) in the "Perimeter" section above.

7A Solution:
 Dig a new post hole right next to the existing post.
 By the way, you can see the big concrete footing for the existing post. It goes down 2 or 3 feet and probably weighs as much as I do!

8A Here I have inserted the new 4x4 post and brought concrete up close to the surface. I have cut off the existing post and placed dirt and rocks to take up the empty space. I could then bring the concrete up and taper the top as discussed in the "Concrete" section above - images 10 thru 13.

9A By placing the new post to one side of the existing one, I have made the last fence section right at 8 foot spacing. (The existing fence was about 7 to 7 1/2 foot spacing.)
 So, to help shorten the spacing a bit and also strengthen the corner post, I nailed a 2x4 pressure treated wood board to the existing corner post. I then nailed a second 2x4 right next it (not shown in this picture).
 This shortens the long span a bit. But mainly, it gives me a solid surface to nail the top decorative board to, which helps tie the new section to the corner post - for greater stability and strength. (See image on the right.)

10A Note that the top decorative board is nailed to the two 2x4 pieces and now joins the back section to the side section at the corner post.
 All the dark stain is due to my spraying some of the preservative on the tops of the 2x4s prior to attaching the top decorative board. I treated the top of the existing corner post last year. (Yes. I oversprayed a bit on one of the new fence slats.)

11A Got a rotten post top?
All but one of the posts in the original fence had a decorative piece laying on top of the post. But the post on the right side of the gate had no cover. No wood can withstand being uncovered - not treated pine, not cedar, not even pressure treated wood.
 I would have preferred to replace the post, but as discussed, that was just too difficult. But it IS possible to "repair" a rotted post top.

12A First, dig out any loose wood. I just used a large needle-nosed pliers. Then spray some of the preservative into the cavity and allow to dry while you finish other things.

13A Fill the cavity with any exterior caulk you have laying around. Allow to dry overnight - it will probably shrink.

14A Apply chocolate cake frosting on top. OK, how about an exterior caulk with a desired color. Use a wide spatula if you have one to smooth it out a bit.
 NOTE: This is NOT the final step! No caulk on the planet will withstand exposure to moisture and sunlight when it is spread out like this. Usually caulk is used to fill (small) cracks and fissures. So the final step is to place a post cap on top. The caulk will protect the wood as long as it is capped.
 While you are at it, place a post cap on all posts you have with exposed tops.

15A Here's a simple metal post cap.

Here's the back side, to show the double support boards on the bottom, as well as the cinder block "animal perimeter". These blocks are lined up right underneath the lower support board, with a little spacing. The fence slats on the inward side overlap these cinder blocks and cover the spacing. This works (keeps the chipmunks out) for the type of fence with the slats on one side, due to the close spacing of the slats - about 1/4 inch.

And this picture shows the section that is longer due to adding a new post to the side of the existing one (pictures 9A and 10A above) Since the section is right at 8 feet, I used three support boards on the bottom - to help prevent sagging.
 NOTE: No, this isn't the neighbor's side! This is the back side of the yard, which backs to a really big forest. So I wasn't as fastidious on the appearance of the smaller blocks that are on either side of the post. (As discussed in picture #30 above, the standard-sized cinder blocks won't fit up next to the posts due to the post concrete.)