This article continues our series on how to build a fence. In this phase, we’re covering how to properly lay out your fence line and set your posts—no matter the type of fence you’re building. These methods work for wood posts, vinyl posts, chain-link posts, composite posts, and aluminum posts. Proper layout and accurate post installation are what determine whether your fence ends up straight, sturdy, and long-lasting.

Tools You’ll Need

  • Concrete (60 lb or 80 lb bags)
  • Post hole digger or auger
  • Fence post tamp (for dry-pack installs)
  • Mason line or string line
  • Level or post level

1. Call 811 Before You Dig

Always call 811 before digging any post holes. They will mark underground utilities such as gas, water, sewer, electric, and fiber. This step prevents accidents, expensive repairs, and ensures the fence can be installed safely.

2. Confirm Your Property Line

Next, make sure you know exactly where your fence is allowed to be installed. You can:

  • Locate your survey pins
  • Review your closing survey
  • Reference your county GIS map (approximate only)
  • Communicate with your neighbor if boundaries are unclear

Most homeowners choose to place the fence just inside their property line unless both neighbors agree otherwise.

3. Choose the Fence Path & Corner Locations

Mark the corners of the fence and any direction changes. You don’t need to outline the entire path—just establish the corners, gate openings, and general line the fence will follow. This layout will guide everything that comes next.

4. Set the Corner Posts First

The corner posts determine the geometry and alignment of the entire fence, so they must be installed securely and accurately. You can set posts using either method:

  • Wet-Set Concrete: Mix your concrete with water and pour it into the hole before placing the post. This is the most secure method and prevents movement. If you’re unsure which method to use, always wet-set—especially for corners or chain-link, which will be tensioned.
  • Dry-Pack Method: Pour dry concrete mix into the hole and tamp it extremely tightly with a post tamp. The soil moisture hydrates the mix over time. This only works if the concrete is packed very firmly; otherwise, the post may move. Dry-pack is more of a “lazy-day” method and not recommended for structural posts.

The type of fence can influence which method you choose. Chain-link corner posts should always be wet-set because the fabric will be tensioned against them. Wood, vinyl, aluminum, and composite posts may use either method depending on soil conditions and installer preference.

Important: All gate posts—for every fence style including wood, chain-link, vinyl, composite, and aluminum—should always be wet-set. Gates apply extra leverage and repeated movement to their posts, so it is best practice to use more concrete and a larger diameter hole to prevent any shifting over time.

Recommended Post Depth

Most installers set fence posts between 24″ and 36″ deep. Many authoritative sources recommend a minimum depth of 36″ for a standard 6-ft fence:

When ordering materials, make sure the posts are long enough to accommodate both your fence height and required burial depth. It’s also a professional touch to avoid bottoming out the post directly onto dirt—dig the hole slightly deeper and set a small amount of concrete at the base first. This keeps the post off the soil and reduces settling.

Phase 3: Running String Lines, Spacing Posts & Setting Line Posts

Now that your corner posts are set, it’s time to establish the straight lines and precise spacing that will determine whether your fence looks clean, professional, and perfectly aligned. This phase is critical in how to build a fence, because post spacing and string-line accuracy directly control how straight your boards or panels install later.

Staging Your Materials

Before running any string lines, take a moment to stage your materials. This means placing one fence post at every location where a line post will be installed, along with one bag of concrete per hole (unless your specifications require more).

Staging materials dramatically speeds up workflow because:

  • You eliminate excessive back-and-forth walking
  • You reduce layout errors by seeing your spacing physically in the yard
  • You maintain a logical installation rhythm down the entire run

It’s a small step that makes a huge difference in installation efficiency.

Running Your String Lines

To begin the actual fence layout, run a mason line from corner post to corner post. Make sure the string is placed consistently on either the inside or the outside face of every post—whichever side will guide your pickets or panels.

  • Tie the string line extremely tight
  • Use neon mason line for visibility
  • Be aware that long string runs can move in the wind, so re-check tension periodically

This string line is your master reference for straightness. Every post you set will align to this line.

Post Spacing & Avoiding Short End Sections

Proper post spacing is critical. Nothing looks worse than installing a full fence run only to end up with a tiny 2–3 foot section at the end. The most professional method is to divide the total length of the run into evenly spaced post intervals.

As a general guideline:

  • Wood, vinyl, aluminum, and composite fences: ~8 ft on center
  • Chain-link fences: up to 10 ft on center
  • Prefab panels: typically 6 ft or 8 ft sections

If you are using prefab wood, vinyl, or aluminum panels, you have two options:

  • Option 1: Install using the panel’s factory spacing, and accept that you may end up with an uneven final section.
  • Option 2: Custom-trim every panel to create equal spacing—which works, but adds significant time and labor.

Basic Formula for Even Post Spacing

To calculate clean, even spacing across a run, use this simple formula:

Total Fence Length ÷ Number of Spaces = On-Center Spacing

Where:

  • Number of Spaces = Number of Posts – 1
  • If using wood/composite/vinyl posts, account for post width as needed

This formula ensures your post spacing is consistent and eliminates the “awkward short section” at the end of the fence.

Digging the Line Post Holes

Once your spacing is determined, mark each hole and begin digging. Your hole width should depend on your confidence in accurate spacing:

  • 9-inch diameter: Best for installers who are confident in measuring and marking. Less concrete required.
  • 12-inch diameter: Provides about 1.5″ of tolerance on each side of the post, allowing you to “correct” minor spacing errors.

The only downside to larger holes is that they require more concrete. Plan for roughly one 60–80 lb bag per hole unless your fence specs require deeper or wider footings.

Setting Line Posts to the String Line

With the holes prepared, set each post so that it is perfectly plumb and aligned to your string.

  • Use a post level to ensure the post is vertically plumb
  • Align the post so it barely touches the string—about 1/16″

If the post pushes the string line, your entire fence will drift off alignment. The string should always remain straight, tight, and undisturbed as you work your way down the run.

Next Step: Setting Post Height & Adjusting for Grade

After your posts are spaced and plumbed, the next article will cover how to adjust post height for sloping yards, how to micro-adjust grade changes, and how to create a perfectly flowing top-rail line.

Phase 4: Setting Post Height & Adjusting for Grade Flow

See how the middle fence post is noticeably higher than the two neighboring posts? That’s a perfect example of a micro-grade variance. A professional installer would strategically adjust the post heights so the difference is far less noticeable, creating a smoother, more continuous top line. Instead of relying solely on hole depth, the installer fine-tunes each post so the entire fence flows with the natural terrain.

When most people search for how to build a fence, they’re usually told the same simple rule: dig every hole to the same depth and set every post to the same height. And yes—if you’re DIYing and you want the most basic approach, that method will technically work.

You simply:

  • Dig each hole to the same depth
  • Set each post using the depth of the hole as your height reference
  • Dry-pack or wet-set your concrete

But here’s the problem: real yards are never perfectly flat. Even what looks like a flat yard has small bumps, dips, and grade shifts every few feet.

The Issue With Micro-Grade Variances

If you set every post at the exact same depth without accounting for the natural terrain, you’ll see what professionals call the “stairstep effect.”

For example:

  • One post ends up 1 inch higher because the ground rises slightly
  • The next sits 2 inches lower because the ground dips
  • Looking down the fence line, the top appears wavy, uneven, and unprofessional

This is extremely common—and it’s why professionals don’t rely solely on hole depth. Instead, pros will micro-adjust each post height so the tops flow naturally with the grade and create a visually clean, consistent fence line.

How Deep Should Fence Posts Be? (Industry Comparison)

Most reputable sources in the fencing and concrete industry recommend setting fence posts between 24″ and 36″ deep for a standard 6-foot residential fence. Many follow the “one-third to one-half of the above-ground height” rule.

This aligns directly with our recommendation to plan for 24–36 inches of post depth. When in doubt—especially for gate posts or high-wind areas—it’s safest to target the deeper end of that range.

Where our method goes further than most generic advice is in how we handle the top line. While most guides simply tell you to dig, set, and forget, we intentionally set posts about 1 inch high so the tops can be trimmed later. This allows us to create a perfect flowing top line that follows the natural grade of your yard.

Professional Tip: Set Posts Slightly High

If you’re not confident in micro-adjusting, the safest approach is to intentionally set each post about 1 inch too high.

Why?

  • You can always trim the top of the post
  • You cannot fix a post set too low
  • Trimming the tops later creates a smooth, professional top line

This method works on:

  • Wood fences
  • Chain-link fences
  • Composite fences

Important Note About Prefab Vinyl & Aluminum Fences

If you’re working with prefabricated vinyl or aluminum panels, be cautious when adjusting post height. These systems rely on:

  • Pre-drilled or molded rail holes
  • Fixed rail heights
  • Top caps or post covers that must align perfectly

This means you can’t freely adjust post height the way you can with wood or composite. Follow the manufacturer’s measurements closely or the panels will not fit correctly.

If This Sounds Complicated—We Can Handle It

If you’re unsure what we mean by grade flow, micro-adjusting post tops, or running visually perfect lines, it might be easier to let us do it for you. Our team at Chonko Construction professionally installs fences that follow the terrain smoothly and look right from every angle.

Click here to learn more about our Fence Installation services in Columbia, SC.

For the Purpose of This Guide

If you want the simplest DIY approach, follow this:

  • Dig all holes to the same depth
  • Dry-pack or wet-set your posts consistently
  • Err on the side of setting posts slightly high
  • Plan to trim the tops for final grade flow

If you don’t want to mess with post heights, grade adjustments, and concrete, we can handle it for you. Contact Chonko Construction for professional fence installation, and be sure to check out the rest of our how-to articles on our blog for more fence tips and guides.