Fence & Deck guide
Plan your fence & deck project
Planning the posts
Most wood fences put posts 8 ft apart. Rails are sold in 8 and 16 ft lengths, so that spacing keeps cutting and waste to a minimum. Tall privacy fences in windy places often go to 6 ft spacing for extra strength.
Each straight run needs one more post than it has sections. Every corner, end and gate adds posts of its own, so work out each straight run separately when the fence turns.
Counting pickets
Use the actual width of a picket, not its name. A 1 × 6 picket is about 5.5 in wide. For a solid privacy fence, set the gap to zero. For a picket fence, add the gap you want between boards.
Deck boards
Deck boards run across the joists. The number of rows is the deck width divided by the board width plus the gap; the board length decides how many boards each row needs. Composite decking makers publish their own gap and joist spacing rules, so check the installation guide for your product before you buy.
Fence and deck sizes worth knowing
| Item | Typical figure | Note |
|---|---|---|
| Wood fence post spacing | 8 ft on center | Matches 8 and 16 ft rail lengths |
| Closer spacing | 6 ft on center | Heavier panels or windy sites |
| 1 × 6 picket, actual width | About 5.5 in | Nominal sizes are larger than actual |
| 5/4 × 6 deck board, actual width | About 5.5 in | Use the actual width in the calculator |
| Gap between deck boards | 1/8–1/4 in | Composite brands set their own gap |
Common mistakes
- Using nominal board sizes instead of actual widths.
- Forgetting the extra posts at corners and gates.
- Ignoring the gap between deck boards.
- Skipping the permit check; many towns limit fence height and position.
Frequently asked questions
How far apart should fence posts be?
Most wood fences use posts 8 ft apart on center. Use 6 ft for heavier fences or windy sites.
How many posts do I need for a 100 ft fence?
At 8 ft spacing, 100 ÷ 8 is 12.5, so 13 sections and 14 posts, before adding extra posts for gates and corners.
How wide is a 5/4 × 6 deck board?
About 5.5 in. Use the actual width in the calculator, not the nominal 6 in.
Do I need a permit for a fence?
Often, yes. Many towns set limits on fence height and position, especially for front yards. Check with your local building department before you dig.
Sources
- Hunker, Fence Post Spacing Guide
- The Home Depot, How to Build a Fence
- Trex, How to Easily Space Deck Boards