How to Set Fence Posts That Won’t Rot

Family Handyman

Keep moisture and insects from destroying your cedar fence posts.

Next Project
Time

A full day

Complexity

Intermediate

Cost

$51–100

Introduction

Cedar has a reputation for durability, but unless a few guidelines are followed, cedar posts can fail in as few as five years. Three factors contribute to this early failure: poor drainage, low-quality wood and poor protection against insect damage. Here's how to install new cedar fence posts and avoid the problems that made your old posts rot.

Tools Required

  • Bucket
  • Caulk gun
  • Paintbrush
  • Posthole digger
  • Shovel
  • Trowel
  • Wheelbarrow

Materials Required

  • Acrylic caulk
  • Aggregate
  • Cement
  • Wood preservative

Project step-by-step (5)

Step 1

Pick the Right Posts

  • Don’t use posts that contain sapwood. Instead, use heartwood, because it’s denser and more insect-resistant.

Step 2

Treat the Post With Preservatives

  • Soak the bottom of the posts in a wood preservative containing copper napthanate, such as Cuprinol.
    • Note: Available at some paint stores and home centers, this wood treatment is specifically designed for in-ground applications.

Step 3

Insert Aggregate

  • Place about 6 inches of aggregate in the bottom of the posthole to allow for drainage.
    • Pro Tip: The bottom of the post should extend a few inches into the aggregate as shown.

Step 4

Pour in Concrete

  • Concrete should be 2-3 inches above the soil level.
  • Trowel the top smooth and slope it so that water runs away from the post.

Step 5

Caulk Around the Fence Post Base

  • Apply high-quality exterior acrylic latex caulk, or silicone specifically designed to adhere to concrete, at the base of the post.
    • Note: This will seal the gap between the concrete and post that's caused by freeze/thaw cycles.