If your cedar fence posts are rotting at the bottom, you need to replace them. The rot is probably due to improper installation. If you install your new posts the same way the old posts were installed, you’ll just have to do the whole thing over again in a few years.
Cedar has a reputation for durability, but unless a few seteps are followed, cedar posts can fail in as few as five years.
3 factors contribute to this early failure: poor drainage, low-quality wood and poor protection against insect damage.
To get the most out of your new posts, here are 5 things you can do:
1. Soak the bottom of the posts in a wood preservative containing copper napthanate, such as Cuprinol. This wood treatment is specifically designed for in-ground applications.
2. Place about 6 in. of aggregate/gravel in the bottom of the post-hole to allow for drainage. The bottom of the post should extend a few inches into the aggregate.
3. Pour the concrete so that it’s above the soil level. Trowel the top smooth and slope it so that water runs away from the post.
4. Apply high-quality exterior acrylic latex caulk, or silicone designed to adhere to concrete, at the base of the post. This will seal any gap between the concrete and post that’s caused by freeze/thaw cycles.
5. Don’t use posts that contain sapwood. Sapwood is lighter in color (usually yellow) than heartwood, which is dark. Use heartwood instead. It is denser and more insect-resistant.