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I was wrong about using a 3-inch auger for all my post holes
For years I used a 3-inch bit for every 4x4 post, thinking it was fine. Then I did a job in Springfield last month where the soil was pure clay, and half the posts had a slight wobble after a week. My buddy convinced me to switch to a 6-inch bit for the bottom foot and fill it with concrete, and the difference in stability is night and day. Has anyone else found that a wider base is needed for certain soils?
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henryt185mo ago
That 3-inch bit for a 4x4 post is actually way too small even in good soil. A standard 4x4 is about 3.5 inches wide, so a 3 inch hole barely leaves any room for gravel or concrete around the sides. I switched to using a 10 inch auger for the bottom foot of all my fence posts in rocky soil, then just cement the top few inches. The key is getting that bell shape at the bottom, which gives you way more holding power without using a ton of concrete for the whole length.
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mark_green5mo ago
Man that bell shape trick for rocky soil is genius, I've been fighting a similar battle with my own fence line and wish I'd thought of that sooner. Totally feel you though, nothing worse than digging a perfect hole only to realize you skimped on the width.
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kelly_patel7mo ago
Pure clay needs that wider base, yeah.
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barbara_jenkins667mo ago
Remember that whole trend of making those wonky pinch pots in high school art class? I was so focused on the fancy shape I always forgot the base, ended up with a whole shelf of wobbly little disasters. The teacher just kept pointing at the wheel and saying "foundation first" in this tired voice.
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taylor.william7mo ago
Read this thing about old pottery methods where they'd spend days just getting the bottom slab right before even thinking about the sides. They'd pack the clay, let it dry a bit, pack it more. Makes sense now, a wonky base throws off the whole balance. Your teacher was onto something, even if she sounded done with it.
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