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I am buildings a 16x24 log cabin in rural West Virginia. It will not have electric, running water, or any type of HVAC. One of the biggest worries I have, as I feel I should, is the foundation. I am planning to use 18 12" diameter concrete footings (pillars) and have a few questions about doing this.

  1. Does anyone know where to find the official frost line for northern West Virginia? I looked all over and found different answers (between 12 and 36 inches) and just want to make sure. Most answers were around 30" so if there is not an official number available I am going to go with that.

  2. Do I need to have a flat piece or pyramid at the bottom of the footing? I've read that it is totally necessary but have watched multiple videos where the builders did not do this.

  3. How deep below the surface can I end the footing at? Sorry if that is worded poorly but I don't know how else to ask it. I do not want any concrete sticking out of the ground as I think that would ruin the log-cabin vibe but I have not been able to find any info on this. I saw a finished model of what the cabin will look like and the treated 6x6s went into the ground, I'm just not sure how far.

Any insight is very helpful. I am quite new to this but I am determined to make it work by educating myself and thinking ahead.

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    Your county building inspector can probably give you that information, even if you don't need a building permit. – Stephen Daddona Jun 22 '20 at 23:42
  • To give you an idea of footing depth, I live in Central Indiana and our frost line is 32", so footings have to be deeper than that. According to this climate map from Wikipedia Northern VA is warmer than where I am, so your frost line should be higher, so the 30" number you got sounds reasonable. 32" footings should be sufficient. (Specifically not an answer, just more info. Consider Wiki an ok source of info, consult your building inspector.) – FreeMan Jun 23 '20 at 12:13
  • Erm... Sorry, you're in WV, not VA - I forgot which while I was looking at the map. However, the climate data indicates they're essentially the same unless you're up in the mountains. – FreeMan Jun 23 '20 at 14:03
  • You can make the footings just pads 12" thick if you like. They don't have to come up near the surface if your posts are suitable for ground contact. That's why the concrete is usually above grade. – isherwood Jun 23 '20 at 14:42
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I use the extreme cases when preparing footings, the map I looked at showed 36” would be an extreme condition and as such constant frost heave at that depth will not be a problem. As far as your piling I have done quite a few homes and never shaped the bottom other than flat, if using a auger to drill your holes they do end up with a bit of a point.

I usually put a couple shovels full of rock in the hole so the concrete doesn’t mix with dirt as it is pumped/ dumped in the tube, code in my area requires the piling to be 6” above grade, small diameter piling (less than 18”) also require tubes to prevent dirt contamination and a 5000 psi mix .

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  • Could you link to the map you looked at to help out the OP (and others). Also, "code in my area..." indicates to the OP that he needs to check his local codes unless someone else chimes in with references to his neighborhood. – FreeMan Jun 23 '20 at 14:02
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    I looked up national weather service frost depth , typed west va in the search box and it gave a light blue or 24-36” this makes sense since January average low is 21.7f . With a more specific location it could be shallower but since we are really only talking 1/2 a yard concrete difference I would stay on the safe side. – Ed Beal Jun 23 '20 at 15:34
  • @EdBeal I was going to downvote this because you say the concrete in the piling is required to be 5,000 psi. This is not true. There is nothing in the Code that stipulates the compressive strength of concrete, except a minimum of 2500 psi for structural systems. However, some of your other info is correct so I decided to just cite you rather than downvoting. Be careful when you make up info. The op could end up believing it and you could harm someone. – Lee Sam Jul 23 '20 at 16:27
  • @EdBeal Btw, you might say “the piling was designed by an architect or structural engineer and they required 5000 psi.” Rather than implying 5000 psi is minimum. – Lee Sam Jul 23 '20 at 16:48
  • @lee sam I did not make that up it was specified on the pilings and foundations on buildings I built it may have to do with I live in earth quake country but not made up. And as I said in my area. – Ed Beal Jul 23 '20 at 21:49

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