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Had a real wake-up call about post hole depth last month
I was putting up a 6 foot privacy fence in Cedar Rapids, using my usual method of digging about 24 inches deep for the posts. The ground felt solid, so I figured it was fine. Then we got that big storm three weeks ago, the one with 50 mph winds. Went back to check the job and three posts were leaning bad, like a good 4 inches out of plumb. The client was not happy. I pulled one and saw the concrete base had basically just rocked in the hole, it wasn't anchored deep enough at all for that height in our soil. I've been setting posts for 8 years and just always used that 2 foot rule of thumb. What other depth guidelines do you guys follow for different fence heights?
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blairc901mo ago
@blake792 nailed it actually, the rule of thumb is just a starting point. For a 6 foot fence in heavy clay like Cedar Rapids, you really need to go at least 30 inches, maybe even 36. I learned this the hard way too after a job in Iowa City where the frost line is deeper than people think. Another thing nobody mentioned - the soil type matters way more than the fence height. Sandy soil drains different than clay, so your hole depth has to adjust for that. Take this with a grain of salt, but I always dig test holes around the property first to check the soil composition before setting any posts. It adds an hour to the prep but saves you from pulling leaning posts later.
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blair_ward393mo ago
Honestly I've always gone deeper than that, like a third of the post height at least.
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