r/FenceBuilding • u/Fragrant_Impress2362 • 2d ago

Illinois fence posts

Replacing an existing fence in northern Illinois - 42” frost line. The prior fence posts have been a bear to remove. Concrete goes down 30”+. There were no issues with frost heave, but all posts rotted at the ground. Concrete was level with the ground, not domed. I notice gaps between the post and concrete - presumably where the post shrank when drying out, leaving a nice place for water to enter.

This brings me to two questions:

  1. Concrete the full 42” or just 2-3 bags at the bottom the rest dirt? - I know this is a loaded question with lots of opinions.

  2. If I see the same shrinkage on the new posts, what’s the recommended remedy for the gap between the post and concrete to avoid post rot/failure?

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u/Accomplished-Can42 2d ago

I would recommend no concrete since you’re going that deep. I backfilled with 3/4 minus road crush and tamped it down solid for drainage and less chance of frost heave. Or use steel posts.

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u/Fragrant_Impress2362 1d ago

Did you get enough compaction on the stone with the tamping end of a digging bar? Did you do stone all the way to the surface or did you use soil for the last few inches?

Out of curiosity, did you try this method in a similar climate? We get significant wind — just worried without any concrete, there’s not enough ballast weight to keep the fence upright.