Fence Building Tips
Updated: Jan 7, 2022
An air-powered framing nailer will be your best friend when building a wooden fence.
They say good fences make good neighbors. Here are a few tips for fence construction that we’ve learned over the years.
Plan your fence by sketching a rough design on paper, listing its length, height, style, number of posts and stringers. To determine the amount pickets you’ll need for the fence, first calculate how many pickets you’ll need for one panel section between two posts (based on picket width and desired pattern), then multiply that figure by the total number of panel sections.
For a 6-ft. tall wooden privacy fence, the support posts can be made from 8-ft. treated 4×4s. The posts should be approved for ground contact. The horizontal stringers (also called fence rails) can be made from 8-ft. 2×4 treated boards. Treated lumber is the most common and budget-friendly choice for fencing.
First, pinpoint the location of each corner post. Drive stakes into the corner-post locations and run a taut string between the stakes. Walk the fence line with your tape measure and spray-paint an “X” to mark each post. Fence posts are usually 6 to 8 feet on center. The closer the fence posts, the stronger the fence. Be careful not to space the posts any wider than the length of your stringer boards. When laying out the fence, keep in mind the ends of the stringers can be toe-nailed or fastened with hardware between two posts, or the stringers can be face-nailed to the outside of the posts, with the stringer-ends butting together in the middle.
A drain spade and a post-hole digger are two tools that prove useful during fence construction.
A post level features separate plumb vials that measure two adjacent faces of a post at once.
When digging post holes down here in Alabama, a good rule of thumb is to dig a 1/3 the depth of the overall post height. A 6-ft. tall post requires a 2-ft. hole and an 8-ft. 4×4, since you’ll be burying the bottom 2 feet of the post. Plus, you should add about 4 inches to that digging depth, so you can add a bed of drainage gravel before setting the posts. The holes we dig usually measure 12-18 inches wide.
Note that colder climates might require deeper post holes to avoid frost heave. Check your local building-code guidelines regarding recommended post-hole depth. Before digging, it’s also a good idea to call “811” nationally to get any underground utility lines, cables and pipes marked for free.
Align the fence posts between the corner posts using a taut string as a guide.
The white board is a story pole, which is a scrap board that I marked with black tape. The tape indicates the locations of each stringer height. I place the story pole against each fence post and mark the stringer placement for later.
Set the corner posts first. Make sure the square face of the posts align with the fence path. I recommend plumbing the posts using a post level, which features level vials that measure two adjacent faces of a post at the same time.
You can use ready-mix concrete sold in bags to set the posts. Once you have the corner posts held in plumb position (using braces or an assistant), pour the mix into the hole dry, straight from the bag. Once the post base is covered, pour water over the dry mix according to the amount recommended on the package. For sturdy fence posts, we recommend using about 75 lbs. pounds of dry concrete per post.
You can pour the ready-mix concrete around the post base while it’s still dry, then add water.
Run a taut string between the corner posts as a guide to mark and position the remaining fence posts. Keep the string on the outside face of the posts and secure it tightly. Set the remaining posts in the same manner, making sure their outside faces are plumb and lined up exactly with the string to keep the fence straight.
Allow all the posts to set for 24 hours. Once the concrete has hardened, cover it with dirt and use a hand tamper to compact the ground around the bottom, sloping the soil away from the post.
On this fence we opted to face-nail the stringers over the posts.
For a standard 6-ft. tall fence, we usually position the bottom stringer 10 inches up from the ground. (You might need to alter placement, depending on the height of your fence.) Space the other two stringer rails evenly apart. The spacing between posts usually varies, so each stringer should be measured and cut to length individually to fit the panel sections. Keep a circular saw and sawhorses handy to cut the stringers.
A pneumatic framing nailer will greatly speed up fence installation. Fasten all connections using hot-dipped galvanized nails (3- to 3-1/2 inches long) with ringed shanks for extra holding power. Make sure your fasteners are approved for exterior use in chemically treated lumber.
We used the edge of a board as a spacing block.
I usually build with three stringers per panel section to prevent the fence boards from bowing, but since this fence had two layers of pickets nailed together, the homeowner decided to stick with two stringers.
If you plan to conceal your posts behind the fence boards, use a reciprocating saw to chop off all the post tops at the same height prior to installing the fence boards. If you plan to leave the posts exposed above the fence pickets, you can cut them later.
Attach the fence boards or pickets securely against the stringers. Your choice of fence style will determine the picket spacing. On the “double picket” fence shown in the photos, we used the edge of a fence board to keep the gaps consistent.
Place the first picket along the corner post and drive one nail through the board at the top. Use the nail to pivot the board you use a 4-ft. level to find plumb. Once in position, finish nailing the board in place, using at least two nails per stringer location. Place the spacer block next to the first picket and position the second picket against it. Nail the second picket using the same pattern at each stringer location. Repeat for all pickets.
The two picket layers were face-nailed together, with the joints staggered between layers.
To make sure the fence boards line up consistently, you can level the ground between each pair of posts and lay a temporary 2×4 flat along the ground. By sitting the pickets on the 2×4, the board tops install in a straight line, and the gap beneath them (once the 2×4 is removed) keeps the board ends off the ground to reduce moisture damage and rot.
On the fence shown, we covered the first layer of fence pickets with a second layer, using the same spacing pattern but staggering the joints. The second layer adds strength and rigidity to the fence.
Each post top was cut level in preparation for a post cap. Post caps protect the posts from rain and moisture soaking into the wood’s end-grain and causing rot.
Protect your new fence with a waterproof stain/sealer, which also provides the opportunity to apply your color tone of choice.
We cut the posts in preparation for post caps.
Here is the fence as the neighbors will see it.
Post caps protect the posts from rain and moisture soaking into the wood’s end-grain and causing rot. Photo © DeckoRail