🪵 Fence Calculator | Gjerdekalkulator

🌳 Posts (4×4 timber, typically 4-6m long)

What: Vertical beams that hold up the entire fence. The backbone of your structure.

How many: Space them 1.8–2.4 meters (6–8 feet) apart. For a 10m fence: 5–6 posts. For a 20m fence: 9–11 posts.

Why: Without strong posts, your fence will sag or fall over in wind or when someone leans on it.

Typical cost: 400-600 NOK each (Norway baseline estimate)

🪵 Rails (2×4 or 2×6 horizontal beams)

What: Horizontal beams that connect posts together and hold pickets/boards in place.

How many: Usually 2–3 rails per fence (top + bottom, sometimes middle). For a 10m fence with 2 rails: ~20m of rail material.

Why: Rails distribute the load and prevent posts from shifting sideways. They're what everything else attaches to.

Used by: ALL fence types

🎨 Pickets (narrow boards, 1×4 or 1×6)

What: Vertical boards with gaps between them that make up the decorative picket fence.

How many: Typically 8–10 pickets per meter. For a 10m fence: 80–100 pickets.

Why: Creates the classic fence look. Gaps allow airflow and sightlines.

Used by: Decorative Picket fence only

📦 Boards (larger boards for solid fences, 1×6, 1×8, or 1×10)

What: Full-size boards that create solid (no gaps) privacy fencing.

How many: Usually 10–15 boards per meter (depending on board width). For a 10m fence: 100–150 boards.

Why: Creates complete privacy. Blocks sightlines and reduces noise.

Used by: Privacy Screen, Shadow Box, Horizontal Slat fences

🔩 Screws (3-inch galvanized or stainless steel, typically 100-count boxes)

What: Metal fasteners that hold boards/pickets to rails and rails to posts.

How many: Use 2 screws per picket/board (one at top rail, one at bottom). Each 100-count box covers ~50 boards.

Types:

• 3-inch deck screws: For attaching pickets/boards to rails
• Lag bolts (4-6 inch): Optional, for extra-strong rail-to-post connections

Why galvanized/stainless? Rust resistance. Regular steel screws will corrode and fail in 2–3 years.

Used by: ALL fence types

🔨 Concrete (60kg bags, typically mixed on-site)

What: Powder mix (cement + sand + gravel) that sets posts in the ground permanently.

How many: ~2 bags per post (120kg total). For 6 posts: ~12 bags.

Depth: Post holes are typically 60–75 cm deep. You fill the bottom 40–50 cm with concrete.

Why concrete? It locks posts in place so they don't shift or rot. Ground moisture + wood = rot without concrete as a barrier.

Pros: Extremely durable (20+ years), affordable, proven method

Cons: Heavy to carry/mix, requires digging holes, requires curing time (24+ hours)

Used by: ALL fence types (this is non-negotiable for durability)

🔩 Ground Screws (Metal spiral anchors, alternative to concrete)

What: Large metal screws (M16–M20) that you twist directly into the ground to anchor posts. No digging required.

How many: 1 ground screw per post. Typical length: 60–90 cm.

Cost: ~200–400 NOK each (more expensive than concrete, but saves labor).

How to use:

• Mark post locations
• Twist screw into ground using a socket wrench or power drill (for hard soil)
• Takes 5–10 minutes per post (vs. 30+ min digging + 24hr cure for concrete)
• Attach post base bracket to screw hub above ground

Best for:

• Rocky or hard soil (where digging is very difficult)
• Temporary or removable fences
• Quick installations (no curing time needed)
• Sloped terrain (no need to level holes)

NOT ideal for:

• Soft, wet, or clay soil (less grip)
• Large/heavy fence (may not be as stable as concrete in extreme wind)
• Very cold climates (ground freeze-thaw can loosen)

Pros: No digging, no curing time, reusable, easier for hard soil

Cons: Higher cost, less durable than concrete (8–12 years), may loosen over time in freeze-thaw

❓ Concrete vs Ground Screws: Which Should You Use?

Choose CONCRETE if: You have soft soil, want maximum durability (20+ years), or are on a budget

Choose GROUND SCREWS if: You have rocky soil, need quick installation, or plan to relocate the fence later

Best practice in Norway: Concrete is the standard for permanent fences. Ground screws are growing in popularity for DIY projects and removable installations.

❓ Do You Need Post Screws?

No, not usually. "Post screws" typically refer to fasteners for metal structures. For wood fences:

• Use lag bolts (4–6 inch) if attaching rails to posts requires extra strength
• Use 3-inch deck screws for attaching pickets/boards to rails
• Use concrete to set posts in ground (not bolts)

🎯 Material Combinations by Fence Type

• Decorative Picket: Posts + Rails (2) + Pickets + Screws + Concrete ✓
• Privacy Screen: Posts + Rails (2–3) + Boards (no gaps) + Screws + Concrete ✓
• Post & Rail: Posts + Rails (3–4, no boards) + Screws + Concrete ✓
• Shadow Box: Posts + Rails (2–3) + Boards (staggered, alternating sides) + Screws + Concrete ✓
• Horizontal Slat: Posts + Rails (2–3, horizontal) + Slat boards (horizontal, not vertical) + Screws + Concrete ✓

💡 Quick Estimation Formula

For a 10m fence, 1.2m high:

Posts: 10m ÷ 2m spacing = 5 posts + 1 extra = 6 posts
Concrete: 6 posts × 2 bags = 12 bags
Rails: 10m × 2 (top + bottom) = 20m rails
Pickets/Boards: 10m × 8–10 per meter = 80–100 units
Screws: (100 pickets ÷ 50) × 1 box = ~2 boxes

Phase 1: Build a Fence That Just Works

• Set permanent posts at 1.8-2.2 m spacing (future-ready frame).
• Install top and bottom rails.
• Add gate posts and gate framing now, even if gate style upgrades later.
• For lowest cost starter mode, choose Post & Rail or simple privacy boards.

Phase 2: Upgrade the Look When Budget Allows

• Add infill boards, pickets, or horizontal slats onto the same frame.
• Upgrade section-by-section (front yard first, sides later).
• Keep the same post spacing and rail heights to avoid rework.

Phase 3: Premium Finish

• Seal/stain paint-grade timber.
• Add post caps, trim boards, lighting, and decorative gate hardware.
• This is aesthetic only. Structure remains from Phase 1.

Modular Rules That Save Money

• Do not change post locations after Phase 1.
• Use corrosion-resistant fasteners from day one.
• Design rails for your final target style now, even if infill comes later.
• Buy structure first, appearance second.

Quick Start (60 seconds)

• Draw one or more fence segments on the map, or type fence length manually.
• Set post spacing (typical range: 1.8-2.4 m).
• Add door openings so those sections are excluded from infill materials.
• Choose fence style and confirm pricing.
• Read the phase totals and materials list.

Core Equations

Posts: ceil(length / postSpacing) + 1

Effective infill length: length - doorOpenings

Rails: effectiveLength × railsPerStyle

Pickets / boards: Based on selected style density per meter

Total: sum(material qty × unit price) + tax

NOK mode uses 0% additional tax because local prices are typically listed with MVA included.

Worked Example (Live)

This section updates from your current inputs so you can validate the logic against your own project.

Safety Margin Rule

Add 10% extra for boards/pickets and screws. This covers cuts, mistakes, and future repairs.