Alternatives to concrete footing

Hi there,

I'm up in the frozen North of New England and am putting in a semi-permanent compost bin structure. I'm sinking the uprights down about 2 feet (beyond that, I'd need a jackhammer to get through the rock). I'd like to put in a footing to hold the uprights in place and fight winter heave insofar as possible. I'd rather not use concrete because it's not great for the environment. Do any of you clever folks have a practical alternative? I've heard of hempcrete... Might that work in this case? Other ideas?

Thanks

Double check me on this, but I beleive in my hempcrete research I found that when exposed to moisture it will evertually erode, and in building I know it can not be used for loadbearing.

I know very little about construction, but saw wall designs that were piled rocks encased by wire, might this be an option?

Andy John wrote:Double check me on this, but I beleive in my hempcrete research I found that when exposed to moisture it will evertually erode, and in building I know it can not be used for loadbearing.

I know very little about construction, but saw wall designs that were piled rocks encased by wire, might this be an option?

Would be really hard to get it situated well. We have a spot where we are putting the bins that is basically a flat hilltop that is on top of a bunch of rocky glacial till. No idea if that was all just there and got buried in by dirt or if it's where the farmers in 1800 dumped the rocks from the field they plowed below, but it's dicey getting 2 feet dug and I sure as snot don't want to dig any more around it to allow for shaping wire.

I'm thinking of just doing pea gravel + tamper and hoping for the best. In the final analysis, it's a damn compost bin so if it is a little out of plumb I don't think the gods will descend from Olympus in wrath and fire. 🤣🤞

Hempcrete uses Portland Cement, so you would still be using the high embodied energy of the portland cement, while making no use of hempcrete's insulative properties ;)  Kind of worst of both scenario. Use rot resistant wood for the posts to begin with, but then you're on the right track with tamped in gravel. You're giving water plenty of opportunity to get out, not just get in and you're sitting on bedrock at the bottom.. Try to make certain your posts aren't sitting in a basin in the bedrock, someplace water will tend to collect.

To avoid frost heave, I would dig at least a foot around the post on all sides and backfill with the largest, most jagged rocks you can, filled in with tamped gravel. You want crushed gravel, not smooth round pea gravel. If heave happens, the whole area will move up and down, not just the post.

Does the structure really need a foundation pe se?  Can it float on top of the ground?  Probably 35 years ago I helped a neighbor put in a barn in MN that rested on Tammerack beams laying on the ground.  It is still standing.

John F Dean wrote:...... I helped a neighbor put in a barn in MN that rested on Tammerack beams laying on the ground.  It is still standing.

FWIW, for most smaller buildings now (heavy clay soil, northern Minnesota), I just build on the ground and don't bother to sink posts.  At this point, the greatest concern with this approach would be tornados, ...... and I'll take that risk, but all depending on the height X width/length ratio.  Ground heaving is such a problem in this region that I find it better for such structures just to shim them when they go out of level.  On top of which, having many of these structures on skids has paid off in being able to move them to other parts of the property.

I have a 14x28 shed that just sits on blocks at about a dozen spots. I'm moving it to a new area (after I level it of a little better) and was thinking about pouring a footer - but then I figured I'll just make a foundation out of tamped blocks and call it done. They make some big screw in anchors I was planning to put on all four corners and attach w/ steel cable in case of extremely heavy winds. I like the idea of jacking it up and shimming when (not if) things start to move.

D.W.

If this were a typical project, this would be somewhat like putting a mailbox or putting a 4x4 post in the ground for a deck correct?  I mean that you would likely dig the post hole, toss in a little bit of rock at the bottom or maybe some portland cement mix and let it draw moisture out of the ground to set, making the 4x4 really set well into the ground.  Do I have this about correct?

An alternative that uses far less energy is to acquire some lime dust.  my 400' long driveway was started by scraping off the topsoil and then spreading a nice, thick layer of lime dust.  As it worked its way into the clay beneath turned into something like a flexible concrete.  It is very, very solid, yet does not crack.

In your case I would dig the hole, drop in about 2" of lime dust and pack in with the post.  I would then set the post and dump the lime dust all around the post inside the hole.  Perhaps you could place in a few inches of dust, pack down with some type of rod (a crow bar might work well here) and add more dust until you reach the top.  Even dry, the post will immovable and with time, as the moisture is drawn in the lime dust will become very hard but not crack.

By now my driveway is almost as hard as cement, but there is no opportunity to crack as the lime dust is not rigidly held together.  It nonetheless supports great weight and I suspect that a post will be very solid if held in place by lime dust.

Just a thought,

Eric

Peter Ellis wrote:Hempcrete uses Portland Cement, so you would still be using the high embodied energy of the portland cement, while making no use of hempcrete's insulative properties ;)  Kind of worst of both scenario. Use rot resistant wood for the posts to begin with, but then you're on the right track with tamped in gravel. You're giving water plenty of opportunity to get out, not just get in and you're sitting on bedrock at the bottom.. Try to make certain your posts aren't sitting in a basin in the bedrock, someplace water will tend to collect.

Yea, I realized as soon as I started Googling it that there are basically three options for foundation-type stuff:

1. a cement-containing option
2. gravel
3. pre-fab ticky tacky polyiso foam panels

So gravel it is!

Also realized that hempcrete is a no-no for foundations because it biodegrades, so anything getting wet turns it slowly into soup! Haha!

And it isn't right on bedrock, it's more like there's a pile of boulders with dirt on top. We dug out about 24" of small to medium rocks (I define medium as something I can just barely lift out with both arms, so probably 100-pounds tops from 2 feet down in a hole) and then we started hitting bigger rocks that would have required us to dig a 10-foot diameter hole to try to get to the edges of them to get leverage to pop them out. And since I reckoned I wouldn't be able to move something that big anyway absent some serious pulley systems, I threw in the towel. Figured ground heave isn't likely to move around giant boulders much anyway. My one concern is that there are gaps between the rocks, so I need to stop pea gravel from just falling into that and disappearing into the bowels of the earth. Not really sure what to do about that. I mean, I could put down some wire, but that will rust away to nothing eventually. Going to try to tamp down some soil into those holes, then add the gravel. In the final analysis, nothing lasts forever: even the sun is going to blow up eventually!

When you say lime dust are you meaning Calcium hydroxide?
I do see where it's used to stabilize soil, seems sort of like soilcrete.
Crushed limestone is also used in road building and has been recommended for post holes.
It evidently compacts into a solid locked together mass.

If packing a post set on bedrock in stone/gravel  is not enough to stop frost heave, maybe spike the posts with large nails?
That way they would be tied into the gravel and resistant to being heaved up.

Alternatively , if you drill into the bedrock at the bottom of the hole you could use a small amount of anchor setting cement to affix a metal post into the bedrock.
That should prevent any frost heave.
If you need wooden posts for some reason,  you could affix them to the metal posts, or even build wooden posts around the metal ones.

Another way to prevent heaving I've seen is concrete blocks that have angled holes cast into them.
The installer drives steel rods,  through the holes thus anchoring the block into the soil .
For your application, you could drill   holes at an angle through your posts ,one on each face, starting at about 2' and going down from there.
Then drive rebar stakes through the holes and into the surrounding soil as far as they will go.
Leave a foot or so of rebar sticking out so it can be bent over and hold the post in place.
The obvious downside of this utterly  unproven approach is the weakening of the fence post due to all the holes.

John F Dean wrote:Does the structure really need a foundation pe se?  Can it float on top of the ground?  Probably 35 years ago I helped a neighbor put in a barn in MN that rested on Tammerack beams laying on the ground.  It is still standing.

Well, I must confess the extent to which I am an utter greenhorn here. I am following Will Bonsall's advice in his book on self-reliant gardening. Yes, I realize the irony on relying on someone for self-reliance. That is how life in the 21st century do!! But he recommends sinking it 3-foot and putting in a footing. He's up in Maine which gets significantly cooler in the winter. I still wanted 3-foot anyway, but it's just not going to happen what with the rocks and all. So I reckon 2-foot onto big rocks that are themselves on top of more rocks (rocks the whole way down!) would be less likely to heave than soil, though I don't doubt there could be weathering of the rock over time causing cracks and deformation.

The last and only time I ever built a compost bin, I built a tiny thing out of 4 upright posts and chicken wire. It got the job done admirably for how ramshackle it was, but it was slow-going, and I definitely wouldn't stake the health of my food crops on it moving forward, i.e. it is very likely it didn't get hot enough to cook parasites, spores, and viruses sufficiently as it was just too tiny of a system.

I'm going for something with more of a full-throttle output with a 3-bin system so I always have new compost, turned-once compost, and curing compost. Good times.

Also going to make a 2'x4' worm bin which should process 4-8 pounds of scraps a day. We have rescue pet rabbits (four of them; they are ADORABLE!!!) so we have many hundreds of pounds of rabbit poo, rabbit pee, and hay (ye gods, so much hay!!) that we toss out per annum. Reckon it could be going into compost or/and worm pooh.

Come to think of it...would that make worms a sort of poop-beast? Not sure what they would do with rabbit droppings. I am now having a better day because I have been reminded of Dr. Wheaton's colorful moniker for scatophageal organisms.

Edit: Here is the method I'm following: https://www.scribd.com/document/265332008/Composting-as-if-It-Mattered-Introduction-Will-Bonsall-s-Essential-Guide-to-Radical-Self-Reliant-Gardening
Only caveat is I'm doing 3 compartments instead of 5. 5 just seemed excessive for my needs since I've got a relatively small plot of land. I am plotting the dominion and conquest of my entire hilltown eventually, so once I have 500-acres I will kick it up a notch to a 5-bin system. :D

I do wonder why a compost bin needs posts sunk into the ground. I would think the sides fastened to corner posts would keep the whole bin upright, and there is nothing trying to shift a compost bin. If it heaves, the whole thing will move as a unit. If you want a larger bin than sides can reasonably hold together, you could subdivide it into smaller units. Then you can fill and maintain each section on its own schedule. A few removable planks at the bottom of one side would allow easy cleanout.

Even if you want wire sides, boards top and bottom and diagonal would secure the structure.

Tyler Greene wrote:I have a 14x28 shed that just sits on blocks at about a dozen spots. I'm moving it to a new area (after I level it of a little better) and was thinking about pouring a footer - but then I figured I'll just make a foundation out of tamped blocks and call it done. They make some big screw in anchors I was planning to put on all four corners and attach w/ steel cable in case of extremely heavy winds. I like the idea of jacking it up and shimming when (not if) things start to move.

Screw anchors are--and I'm using a scientific term here--pretty badass. I like them. Just wouldn't work in our context because the soil is less digging and more excavation after about 8-10 inches. I haven't got a clue if we can even get stuff to grow here decently given that limitation. We are on top of a hill in the foothills of the Berkshire mountains in western Massachusetts. Not an ideal spot for luscious perennial roots going down 10 foot or anything like that, BUT, there is a mature walnut tree standing nearly 100-feet tall on the same patch of ground, so I know roots CAN establish here, they just have a little bit of a work to do to find a path through the labyrinth of boulders.

Indeed, roots are also pretty badass.

Eric Hanson wrote:D.W.

If this were a typical project, this would be somewhat like putting a mailbox or putting a 4x4 post in the ground for a deck correct?  I mean that you would likely dig the post hole, toss in a little bit of rock at the bottom or maybe some portland cement mix and let it draw moisture out of the ground to set, making the 4x4 really set well into the ground.  Do I have this about correct?

An alternative that uses far less energy is to acquire some lime dust.  my 400' long driveway was started by scraping off the topsoil and then spreading a nice, thick layer of lime dust.  As it worked its way into the clay beneath turned into something like a flexible concrete.  It is very, very solid, yet does not crack.

In your case I would dig the hole, drop in about 2" of lime dust and pack in with the post.  I would then set the post and dump the lime dust all around the post inside the hole.  Perhaps you could place in a few inches of dust, pack down with some type of rod (a crow bar might work well here) and add more dust until you reach the top.  Even dry, the post will immovable and with time, as the moisture is drawn in the lime dust will become very hard but not crack.

By now my driveway is almost as hard as cement, but there is no opportunity to crack as the lime dust is not rigidly held together.  It nonetheless supports great weight and I suspect that a post will be very solid if held in place by lime dust.

Just a thought,

Eric

Eric, I like the cut of your jib, dude. I'm going to try this and will let folks know how it goes. If I forget and you're antsy to know, send me a Purple Moosage in 6-months or so.

Will, D.W., everyone,

When I mentioned lime dust, I did indeed mean crushed limestone.  Water, pressure and time gets this stuff pretty solid but not rigid like actual concrete.  It is a pretty good alternative for portland cement.

Eric

I'm with the people that think you don't need a foundation.  A three bin compost area is, in essence, just three, three-sided walls connected together.  My best ones don't have floors in them.  I guess I don't understand why you care if they move a little?  As long as the three pieces are connected together, the whole structure will stay together unless I'm not understanding the goal?

Thanks for the clarification Eric!
Turns out they use hydrated lime in a similar fashion on muddy construction sites.
Makes me want to try both of them!

Trace Oswald wrote:I'm with the people that think you don't need a foundation.  A three bin compost area is, in essence, just three, three-sided walls connected together.  My best ones don't have floors in them.  I guess I don't understand why you care if they move a little?  As long as the three pieces are connected together, the whole structure will stay together unless I'm not understanding the goal?

Trying to maintain 5x8x4 spacing for hot compost optimization. If the posts shift, it starts to pull apart the rest of the structure or so I'm told. I don't have a degree from Construction University, so hell if i know, I'm just following a guide.

I have built a couple of 32" x 32" x 3' high compost bins out of lumber.No posts in the ground, just a box. Mine are four-sided with a couple of planks at the bottom removable for emptying. They have made good compost.

If you want three-sided enclosures for access to turn compost, I would suggest running a board or pole across the front base (flat if you like) so it holds the sides in position. You could add a top board with tabs to hold the top front corners in position while allowing removal for turning or working the compost.

D.W. Stratton wrote:

Trace Oswald wrote:I'm with the people that think you don't need a foundation.  A three bin compost area is, in essence, just three, three-sided walls connected together.  My best ones don't have floors in them.  I guess I don't understand why you care if they move a little?  As long as the three pieces are connected together, the whole structure will stay together unless I'm not understanding the goal?

Trying to maintain 5x8x4 spacing for hot compost optimization. If the posts shift, it starts to pull apart the rest of the structure or so I'm told. I don't have a degree from Construction University, so hell if i know, I'm just following a guide.

I guess that's where we are having a miscommunication.  I don't use posts at all.  My whole 3 bin compost structure just sits on the ground without any posts holding it.  

Eric Hanson wrote:D.W.

If this were a typical project, this would be somewhat like putting a mailbox or putting a 4x4 post in the ground for a deck correct?  I mean that you would likely dig the post hole, toss in a little bit of rock at the bottom or maybe some portland cement mix and let it draw moisture out of the ground to set, making the 4x4 really set well into the ground.  Do I have this about correct?

An alternative that uses far less energy is to acquire some lime dust.  my 400' long driveway was started by scraping off the topsoil and then spreading a nice, thick layer of lime dust.  As it worked its way into the clay beneath turned into something like a flexible concrete.  It is very, very solid, yet does not crack.

In your case I would dig the hole, drop in about 2" of lime dust and pack in with the post.  I would then set the post and dump the lime dust all around the post inside the hole.  Perhaps you could place in a few inches of dust, pack down with some type of rod (a crow bar might work well here) and add more dust until you reach the top.  Even dry, the post will immovable and with time, as the moisture is drawn in the lime dust will become very hard but not crack.

By now my driveway is almost as hard as cement, but there is no opportunity to crack as the lime dust is not rigidly held together.  It nonetheless supports great weight and I suspect that a post will be very solid if held in place by lime dust.

Just a thought,

Eric

Would something like this be what you're saying I should get? https://www.lowes.com/pd/Timberline-Soil-Doctor-Pulverized-Garden-Lime-40-lb-Organic-Lime-PH-Balancer/3058417

Or is this different? This is basically the same stuff you put into your soil to raise the pH, right?

Eric Hanson wrote:
An alternative that uses far less energy is to acquire some lime dust.  my 400' long driveway was started by scraping off the topsoil and then spreading a nice, thick layer of lime dust.  As it worked its way into the clay beneath turned into something like a flexible concrete.  It is very, very solid, yet does not crack.

In your case I would dig the hole, drop in about 2" of lime dust and pack in with the post.  I would then set the post and dump the lime dust all around the post inside the hole.  Perhaps you could place in a few inches of dust, pack down with some type of rod (a crow bar might work well here) and add more dust until you reach the top.  Even dry, the post will immovable and with time, as the moisture is drawn in the lime dust will become very hard but not crack.

So here's what I obtained at the hardware store (pictures).

I'm planning to shovel in a bit of dirt to stop up gaps between rocks in the holes I've dug. Then I'm going to add lime dust about 2" thick. Then I'm putting in the uprights. I've charred the bottom 3' of the posts about 1/8" deep to resist (actually stop, really) rot. I'll pack down the line, get my partner to hold the post plumb, then pour line around it, pack it down as best I can, then surround it with gravel and then dirt, then tamp it all down thoroughly.

These aren't nice, tidy post holes like you might get digging in a prairie. These are jagged and wide because we had to move some bigass rocks. Hence packing around the post as I go.

Here's hoping for the best!

Also showing the wood I've gathered from various "for free" side of the road drops. I think I'm good to go. Any more suggestions?

Should I show the holes?

D.W.

Actually I think your idea is a pretty good one.  I guess I am spoiled with my deep clay soil that makes post hole, well, post holes.  Sorry you have to excavate so much just to bury so little.

ERic

Eric Hanson wrote:D.W.

Actually I think your idea is a pretty good one.  I guess I am spoiled with my deep clay soil that makes post hole, well, post holes.  Sorry you have to excavate so much just to bury so little.

ERic

I knew what I was getting into when I moved up here. I used to live in Wisconsin with black silt loam. Siiiigh. Drawback to Wisconsin is that it's Wisconsin. So I think I can't put on top 🤣

D.W.,
I'm with Trace on "why the need for posts?" Especially given the hardship. Are you supporting a roof over this? That's about the only reason I'd do it. maybe.

I see you are already on your way...

However, I've had plenty of success with no enclosure and also using just a corral made of garden fencing merely hooked into itself by bending over the wires at the ends into hooks.
They beauty of the "less is more" approach, is that turning or moving the pile isn't "unload this bin" and "reload it into that bin "... it's unhook the fence, reset it next door, reload... or no fence, just flop the pile a few feet to the side each turning.
The fence ring is adjustable, as well, so it can be sized to be "full to the top" no matter what you have going in that day/week/month, instead of it being a shallow layer doing nothing.
It's also portable, so you could setup close to the source or close to the end use and avoid hauling so much.

You mention containing as method to increase the heating of your pile, but it's more about feedstocks and size of the pile than if it is contained. (containment is worthwhile if you have pests, and also if you have just about a cubic yard size pile)
If you have more than a cubic yard (3'x3'x3') you can easily get a hot compost going in a simple heap, and even easier if the pile is larger.

With Lime Dust do I need to wet it after putting it down.
I want to use it with gravel for post as well as on a driveway since it sounds like it holds up well.
Just want to do it right.
Thanks

Peter Ellis wrote:Hempcrete uses Portland Cement...

For people reading this down the road, I wanted to mention that I have never seen a hempcrete recipe that uses portland cement. All of the ones I have ever seen or read about use a lime-based binder. However, as several people mentioned, hempcrete should not be used underground.