tin can floor

I know this application may lead to some problems down the road but then again, maybe not. I have a lot of these cans, I needed to come up with a use for them and this actually is working out really good so far. The bottom line is that these things are a really easy way to take up volume and still be rather durable. Currently the project is up a very muddy road and I can't drive in materials til it dries up. The project is a 200 sq ft cabin and save for a little help framing the thing last summer, I have built the entire thing by hand by myself so my approach towards design often revolves around what I can achieve by myself as I am the only one working on this thing bit by bit. With a three inch later of cob on the bottom and a two inch layer on top the whole thing is quite solid, even after just a day of drying. Aluminum cans fill in the gaps where the cans don't line up perfectly. This idea was my solution to going about this building solo with no help. I thought the forum might find it interesting and I appreciate any input, thanks.

Hi Aaron,

Here's somethings you might want to consider:
-how many pound per square inch will my tin floor withstand?
-how thick does my top layer of cob need to be to stop cracking with the flexing of the tin can centers?
-how much does a tin can expand compared to cob in the hottest of summers?
-how much does a tin can contract compared to cob in the coldest of winters?

Do you fill each can with cob? If you didn't, you won't be able to put much weight at all on your floor...no rocket stove and certainly no waterbed.

One way to determine how many psi a empty tin can withstands is to use a 2x6" x8' board as a lever. Attach one end of the 2x6" to a stationary upright capable of a say 5 tons ( maybe use a steel beam with a platform that won't sink). Make sure your upright is taller than a 55 gallon barrel by atleast 8 inches. Place one of your cans in the middle of the 2x6" x8' at the 4' point making sure it is gravity level. Then hang a 55 gallon barrel whose weight you have already determine from the other end of the 2x6". Begin adding water 1 gallon at a time from a 1 gallon container until your tin can crushes.....using Force*distance where force is the weight of the water (8.333 pounds/gallon), you can determine how many pounds per square inch your floor will hold.

Or you can look up the failure point of thin wall tin which you will find isn't very much.  Adobe bricks have about 300lb/square inch limit; i urge you to find both the tensile and compression failure limit of thin wall tin as soon as possible, if you did not fill each can with cob.

It is my humble opinion your building's walls would be better served than your floor to have been built with tin can....but even then I would need to find the heat expansion for tin to see how much cob I would need to cover them up with and I wouldn't have the weight of my roof on the tin can walls....the weight of the roof would need to be on pillars.

At any rate, good luck with your experiment....and be careful!!!

Hey Orin thanks for the input, I appreciate the info on testing the compression but I am much more in the realm of trial and error as the level of personal and financial risk in this project is very low. You are quite correct: no RMH and no waterbed on the cans, but I do have a corner devoted to the future RMH that will have a base of only river cobble and cob, solid as free can get you, and I'll be bunking in the loft. To me, the risk lies in determining how thick the top layer of cob needs to be in order to not affect the cans below, that is why I allowed myself another 5 inches of space that would put me at plane with the doorways. 6 to 7 inches of cob would be quite solid I imagine. The cans are not filled, so I anticipate addressing some issues but the worst case scenario could be addressed by just filling in any impressions or cave-ins with more cob. If I put a table leg or ladder through any of it, I'll just fill it in. The seasonal expansion factor is a good point, I look forward to seeing how it behaves as the season progresses, I guess I have faith in the resilience of my cob mix -the quality of the on-site clay is excellent. I'll keep updating the progress and performance of the floor as this building season continues, thanks again!

If you just cover them with a nice thick tarp, no one will ever be able to sneak up on you again. I wonder if they are going to creak and pop with temperature fluctuations.

Aaron Tusmith wrote:...The cans are not filled... I look forward to seeing how it behaves as the season progresses,

Since you're going to do the empty can route knowing the weakness/dangers, now you have piqued my curiosity: I really want to know it's heat transfer behavior over the seasons. If you have a infrared thermometer, it would be really cool if you could take three readings per day.  An outside reading of the ground and an inside reading of your tin can floor an hour before dawn, noon and at 9pm local time.

I really would like to see readings every 30 minutes for a day in spring, winter, fall and summer but that probably wouldn't get any response at all.  :]

While I wouldn't build my floor with tin cans, I am curious if its thermal behavior suggests it might make a good wall filler like cord wood houses (cord wood walls can take the pressure of a roof though).

Please post temperatures if you get the chance to!

About a year ago I proposed the idea about using the cans as a building medium and that discussion can be viewed here . There ended up being numerous problems with the idea and I have to thank the forum for essentially talking me out of going forward with it. I still do like the idea of a gleaming metal building but if you read through the thread there are many points brought up regarding the downsides of using the cans as a building material, off the top of my head, rust and condensation were some of the main issues. For better or worse I am however moving forward with their use in the floor, considering the pros and cons I am rather confident I can make them useful in this particular application. I DO have an infrared thermometer, I will definitely post some temps once the floor is installed and dry as I am curious as well. I know what I'm doing might seem ridiculous to some but I am fascinated by up-cycling and this type of experimentation is just fun!

Orin Raichart wrote:Hi Aaron,

Here's somethings you might want to consider:
-how many pound per square inch will my tin floor withstand?
-how thick does my top layer of cob need to be to stop cracking with the flexing of the tin can centers?
-how much does a tin can expand compared to cob in the hottest of summers?
-how much does a tin can contract compared to cob in the coldest of winters?

Do you fill each can with cob? If you didn't, you won't be able to put much weight at all on your floor...no rocket stove and certainly no waterbed.

One way to determine how many psi a empty tin can withstands is to use a 2x6" x8' board as a lever. Attach one end of the 2x6" to a stationary upright capable of a say 5 tons ( maybe use a steel beam with a platform that won't sink). Make sure your upright is taller than a 55 gallon barrel by atleast 8 inches. Place one of your cans in the middle of the 2x6" x8' at the 4' point making sure it is gravity level. Then hang a 55 gallon barrel whose weight you have already determine from the other end of the 2x6". Begin adding water 1 gallon at a time from a 1 gallon container until your tin can crushes.....using Force*distance where force is the weight of the water (8.333 pounds/gallon), you can determine how many pounds per square inch your floor will hold.

Or you can look up the failure point of thin wall tin which you will find isn't very much.  Adobe bricks have about 300lb/square inch limit; i urge you to find both the tensile and compression failure limit of thin wall tin as soon as possible, if you did not fill each can with cob.

It is my humble opinion your building's walls would be better served than your floor to have been built with tin can....but even then I would need to find the heat expansion for tin to see how much cob I would need to cover them up with and I wouldn't have the weight of my roof on the tin can walls....the weight of the roof would need to be on pillars.

At any rate, good luck with your experiment....and be careful!!!

Orin, Are you an engineer? I love how you determine the pounds per square inch using readily available materials! (What self-respecting homestead doesn't have a few 55 gal. barrels sitting around, right? ) This is something I have wondered about for many projects and now I have a way of finding out.

I do wonder if filling the cans with gravel or plain soil would make a difference. OR, what about adding a couple of layers of chicken wire over the top and pressing the cob (or a soil/cement mix) through the wire over the filled cans. If it is merely a question of filling the cans to prevent crushing, would something lightweight like sawdust -- which would add insulation -- also do the trick? Would any of those things materially affect the floor strength?

This is an intriguing idea and might be a good way to dispose of "trash" that otherwise would end up in a landfill. In fact, I've considered making trash walls similar to this to surround parts of my garden or to frame raised beds -- only I would use ferrocement rather than cob to cover the debris (basically hollow walls made of fence panels covered in chicken wire with cans, bottles, etc. filling the hollow space, then covering it all with cement to seal it). Walls would not need to be as tough as a floor, but the same questions about differing shrinkage/expansion rates might apply.

Deb Stephens wrote:
Orin, Are you an engineer?

...naw....just a persistent cretin trying to get at good methods and info anyway I can

Deb Stephens wrote:
I love how you determine the pounds per square inch using readily available materials! (What self-respecting homestead doesn't have a few 55 gal. barrels sitting around, right? ) This is something I have wondered about for many projects and now I have a way of finding out.

I do wonder if filling the cans with gravel or plain soil would make a difference. OR, what about adding a couple of layers of chicken wire over the top and pressing the cob (or a soil/cement mix) through the wire over the filled cans. If it is merely a question of filling the cans to prevent crushing, would something lightweight like sawdust -- which would add insulation -- also do the trick? Would any of those things materially affect the floor strength?

...wasn't my idea, I complained about not knowing how to tell if my adobe bricks were up to construction standards, pointing out i didn't have access to university equipment that did compression tests, and whadayaknow, some smart *** physicist, said oh yes you do  -physics rocks btw- everyone has access to it: trick is realizing there are cool applicable ideas behind those math equations.

{removed incorrect thermal statement}... packed dry sawdust would give the cans some integrity but not much. chicken wire works on walls for holding cob and stucco but I'm not so sure it would help with cracking or strength beyond the minimal added strength of the wire which is an elastic strength.

Deb Stephens wrote:
This is an intriguing idea and might be a good way to dispose of "trash" that otherwise would end up in a landfill. In fact, I've considered making trash walls similar to this to surround parts of my garden or to frame raised beds -- only I would use ferrocement rather than cob to cover the debris (basically hollow walls made of fence panels covered in chicken wire with cans, bottles, etc. filling the hollow space, then covering it all with cement to seal it). Walls would not need to be as tough as a floor, but the same questions about differing shrinkage/expansion rates might apply.

Michael Reynolds, the inventor of earthships used this idea and promoted it Reynolds Site. But, if you will notice, he picked his trash carefully: glass bottles and plastic bottles aren't going to rust or expand/contract too much in comparison to his building materials.

I think this is awesome . Please keep updating over time.  You are now our guinea pig. We want the good and bad, pros and cons.

There has never been a better opportunity for someone to install time capsules in their home. Perhaps they could all be placed in one section and then you tell your offspring where they could be found.

If there's a hallway, I think it could be named Tin Can Alley.

This discussion made me reflect and look up some thermal conductivity values (R values are simply the inverse of thermal conductivity values).
On the face of my quick revisit of these values, my statement of "trapped air makes great insulation" appears blantantly false since dry air still has a greater than 1 thermal conductivity.

https://www.engineeringtoolbox.com/air-properties-d_156.html
Thermal conductivity at 0°C and 1 bara:                 24.35 mW/(m K

So packed dry sawdust with lime might be a better solution.

However, from direct experience, trapped air gapped layers of any material, have a greater R value depending on the number of layers trapped air gaps. One example is double pane windows versus single pane windows (you can feel the difference)....or foam material which traps small bubbles of air.

----------layer of other material
sealed small air gap
---------layer of other material
sealed small air gap
---------layer of material

Is the reason is there is no convection heat flows in spaces less than 18" in vertical height in addition to ?

Or it might be because the double pane windows have a true vacuum between the panes and the foam actually doesn't really have small pockets of air but infact small pockets of many vacuums?

The below statement is one can I truly stand behind:
"A trapped vacuum is a great insulator".
....mainly because there isn't any possibility of heat transfer by conduction OR convection....leaving on heat transfer by radiance.


I have to retract the "trapped air makes a great insulator" because its thermal conductivity value clearly says it isn't: I don't argue with gravity even when I fly.

Now those with more experience with heat flow, please weigh in!!!

I was able to work a bit more on the floor the last three days and these pictures were taken yesterday so I am a little further along than they show. I wont report any temperatures until I am sure that it is dry and I anticipate that to take a while. However I have learned a thing or two along the way. The area shown that looks dry was last weeks round and it was exposed to direct sunlight through the door.  It turns out that I have more like one inch of cob over all of the cans as opposed to the two inches I claimed earlier, the floor flexes a small amount in this one area but is otherwise having no trouble supporting my weight. I do only way about 160 so on a human scale there is potential for some issues but with a little more thickness in the cob and a proper drying procedure I doubt there would be any issues with any size human walking around on this floor. The flexing in this particularly dry area produced a few can-like popping noises but then they stopped doing it, so at first they may make a little noise but they seem to settle in with a little weight on top. I was very excited to test out the floor even when I knew it couldn't be fully dry so I would guess that when the cob dries completely and the cans have nowhere to go they will then not move, nor make any sound. At this point I will just have to wait and see until I am done before deciding if this is actually a viable floor option that I would vouch for. I can write much more about that but at the time of writing this I am actually quite pleased with the speed, ease, and results of doing this.

I love your floor,  nice used of materials.
I think I could stand on a single can and be supported,  and I weight 250.
Keep things dry,  and they shouldn't rust.
Even the gaps between cans could serve as a geogrid,  stabilizing the earth.
Your idea about sequestering trash inside of ferrocement  has been explored by a guy on Instructibles known as "Thinkenstein"
He uses fishing nets or window screen rather than steel mesh but the results should be similar.

https://www.instructables.com/id/Trash-Concrete/


https://www.instructables.com/id/TRASH-ROCKS-Eliminate-Unrecyclable-Trash/

https://www.instructables.com/id/Styrofoam-Concrete/

https://www.instructables.com/id/ROAD-REPAIR-with-NYLON-CEMENT/

I was able to take another swing at the floor project the last three days and here are some pics to show where I'm at. Almost done actually, I've got one last section by the door to cap off. I made a gap around what is to be the hearth and I plan on sticking some rigid foam insulation in there and cobbing over it again. If I wasn't so excited to get started I would have used more but hey oh well. So far the sections that have dried are in areas where the cob is unfortunately too thin. In some of the thinner areas when you walk on it it makes a muffled clicking noise that sounds a lot like those clickers they issued the paratroopers on D-Day. What I have done to fix these high spots is to just pound on it with a heavy hammer until the cans bend and cave to the desired height and then just cob over the messiness- pretty easy. That big rectangle on the floor there is to be the access, for the cellar/well/tunnel to china that I am going to dig. I'll frame up a little door that will sit flush with the rest of the floor and then put a little rug over it. All in all this project has been pretty easy and I've done it all myself. The hardest part by far was mixing all the cob, luckily my swales I dug earlier this year were full during this project and I could pull water from there. I would appreciate a little rain, they're almost dry!

This time I completed the rough surface of the tin can floor, there's still a lot to do but this will work fine for this building season. The rectangle there will be dug out over time and hopefully serve as a water source but if it just ends up being a cellar or cool spot to hang out in the heat then that will be fine too. I Also put a bit of insulation around the hearth area, soon it will be cut to the proper height and covered with more cob.

I did something similar, but instead of using cans, I used "wood rounds".

In logging we call these cookies. I used hemlock because here they grow very big in size, but have no value commercially. I just cut 4 inch cookies from the log, kind of like cutting firewood rounds, but 4 inches long instead of 16 inches. I say 4 inches because that was the thickness of my floor. I let them dry so that they would shrink, then pounded a few nails into them on the sides, but not all the way in, just halfway. Finally I arranged them all over my floor. The final step was to pour concrete between them. The concrete worked its way around the nails, then hardened locking them into the concrete.

The whole goal of course was to greatly reduce the amount of concrete I needed to mix for my floor. The rounds also acted as a natural sponge, soaking up oil from my shop and stuff which is why old factories used thick blocks with the wood grain standing upright so that it readily absorbed the oil.

I had a similar line of thinking in that I wanted to get away with mixing as little mud as possible. I had to raise the floor up almost a foot so using the cans was a great way to take up a lot of volume, while still being pretty sturdy. It was a convenient way to avoid having to buy lumber and frame in a floor.

Dale Hodgins wrote:There has never been a better opportunity for someone to install time capsules in their home.

This is such a brilliant idea!  We are having an under-floor system installed in our house which will have areas free where we could do this.  We are thinking of family pictures and pictures of the house before we reformed it.

When I read in the 'dailyish' this was about using tin cans, immediately I was interested. Not because I want to do this myself. But because I know tin cans were a traditional building material. Maybe in several regions, but at least at some Caribbean islands, like the island Curaçao, which I visited several times. I have some photos of such houses (cabins), I will show you the most clear one. As you see they cut the cans open and use them as sheet metal. Often they paint over the entire wall. This one is only rusty

tin can wall

All those cans.....

One question for the author. Where did you get all those tin cans??

I use cans like that in my wicking barrels. But I am hampered in not having enough for all of them.

I'd love to hear an update, Aaron Tusmith!

To get back to the "Physics is Awesome" sentiment, pressure tolerance is extremely affected by mass ratio with the surface inches of contact. So what I'm specifically wondering is whether something like a sofa which has 4 "small surface area feet" put too much pressure on the tin can floor, compared to objects with large surface area to mass ratios? Was the top thickness of the cob sufficient to get a "spread the load" effect? I *really* don't feel like I've asked this very well (high school physics was a really, really, long time ago, and I was accused by the teacher even then of going at the problems in the "most ass-backwards way" he'd ever seen.)

Even if this experiment *didn't* work, or had specific problems, I'd really like to know as that's how we learn to do these things better.

I think this is an awesome experiment.  On the plus side you have an insulated floor, due to all the entrapped air pockets.  I also see the possibility that the cans will escape rust for a good long time as they are not exposed to a supply of oxygen.  I am concerned about the ability of the cob layer to withstand the constant flexing of foot traffic, and in so thinking, would consider a covering of tongue and groove plywood or tongue and groove flooring to be advantageous in distributing the loads.  You'll have to keep us posted as to how it performs over time.

It just so happens I am at the property today and tomorrow, I was working outside all day and didn't see the recent activity on this thread. So I'll write up a quick update and then take some pics tomorrow to post. I finished the floor back in May and once it was dry enough to walk on without leaving a depression I just treated it like a regular floor, or subfloor rather. At this point I intend to add several additional inches of cob to be sure it will withstand future use but with as little one inch of cob in some areas it is surprisingly durable. I insulated the ceiling all summer and the floor held up great under the ladder in every spot I put it in. Note also I did all of this solo so a two person crew could really make it an effective use of materials. More updates tomorrow, I'm writing this on my phone and its taking forever, thanks everyone!

Ok, now I'm home at the computer. Since sometime in May I have been treating this floor like it was a standard plywood subfloor. I just figured if there was any damage I would cob it over. I can say that it is very durable and I would probably use this method again but improve on my execution. I'll try and answer questions that came up and explain my logic in this project. I gathered all of these cans from local restaurants over several months. I just approached them and told them I could use them for a building project and weekly I would come by and pick up a garbage bag full. With my floor, a couch, or bedposts or something heavy with legs would probably create a depression over time but I would bet that a 3 inch cob layer with an oil-hardened finish would stop that from happening with typical floor use. I think the trick in using cans in this way is to tamp and compress a lot before the floor is completely dry. If I had done this (which I did not), the floor would be in much better shape than it is. My theory is that if you dont give the cans anywhere to go then they wont move. Essentially this means tamping out any and all air pockets. At most I am able to work on the cabin 3 days a week during decent weather, so I missed the ideal windows of tamping because by the time I would get back the floor would be too dry. All I was going for anyway was a level-ish surface to work on so I could complete other interior projects in the cabin more easily. All in all my reasoning for this method was that I would either have to purchase more lumber and frame in a floor or I would have to mix up a ton more cob to make up for the volume that the cans take up. So, if we accept ideal building conditions as a given; that is -quality clay, plenty of straw, plenty of help, a few screes, a laser level and a reasonable timeline then I think this method works very well. Also, make sure the cans are clean because there were tiny little ants early on in the season. I washed all of these with soap and water but it seemed apparent that I missed a few spots.

In some areas I set the cans too high and the top layer of cob was too thin. This let to cracking but still it was functional as a floor. In other areas if the cans were set too high then I just lowered them by beating them down with a hammer. It was the quickest way, then I just poured more cob and leveled it of best as I could. In one particular area I beat the cans too much and there ended up a large depression -still fixable however.

I would think it would create great insulation factor, maybe get something like concrete mesh, some type of reinforcement on top of 2" cob layer and add another 3" of cob and should last a long time.
I'm not an expert though
if you get a can failure
[Thumbnail for DSCN1110.JPG]
you can finish off that bottle of jack and then fill in the void

I can get the same kind of problems just pouring concrete floors. Typically what I do is just plan for a leveling layer over the original floor, then when I put tile down, I have a super smooth surface to work off from.

It is just how I do construction, refine until it is perfect.

I see no problems at all with your tin can floor. A round, upright thin object holds a lot of weight. Bridges and buildings are often built on round metal piles which are essentially metal straws driven into the soil until they sit on bedrock. In a bigger form, they are what your tin can floor is proportionally speaking.

I was thinking too, you might want to get a cement mixer the next time. Dump the cans in your cement mixer with water and soap, and wash them that way.

I wonder what might be achieved by adding sand in between the voids of the cans and topping off with a few layers of newsprint before adding the cob?  Seems like I learn something new on Permies every day.

Thomas Tipton wrote:I wonder what might be achieved by adding sand in between the voids of the cans and topping off with a few layers of newsprint before adding the cob?  Seems like I learn something new on Permies every day.

That sounds brilliant as well as easy. This is assuming I am correct in thinking that sand does not settle over time.

Depending on the type of sand, it may settle some, but just like with installing paving bricks, it doesn't seem to be much of an issue.  Sand would certainly lock those cans into position though.

This man is the milestone of evolution

Impressive.

was able to get the floor up to a better grade these last three days, it was a lot of work but very glad to be done with this stage. I am lucky to have decent clay on my property and when compacted, this stuff is as solid as a rock. You can see a large rectangular opening in the floor which is where I obtained most of the material for the floor by excavating there. I intend to develop the cellar there, and with the presence of water seeping in at a depth of seven feet, perhaps I may be able to install a pitcher pump and get some water flowing. At that depth however I was unable to manage the ladder and it was very difficult to get the muddy clay out of the bottom by myself. So, further development of the cellar/well will require some help unfortunately. But, as deep as it is that is appropriate because things can get dangerous from here on out. Next week I will try and do some finishing touches on the floor and smooth it out a bit, looking forward to it.

Sadly this is no longer an earthen floor, which I am pretty bummed about.  But I had to move on, I am doing this entire cabin build alone with only occasional help so I made the decision to use concrete, one bag mixed in with sand. I dry mixed it all and screed it flat, tamped it down then misted it all. During the mixing there ended up being concentrated areas of portland and other areas where there was not enough, it was frustrating to say the least but when you're alone you do the best you can. I'll patch it up where needed and move on to the next project, insulating the ceiling.

Neat project, too bad it didn't work out. It looks like the soil was collapsing into the voids, then moving/cracking?

For future reference, soil distributes pressure fairly well,  with the area that the stress is applied over increasing by a factor of (roughly!) 2x the depth of the soil layer. Or to put it otherwise.... you may have been ok with a deeper cob layer. Maybe not, soil has almost no strength in tension.

https://www.rocscience.com/help/settle/Settle3D/Stress_Computation.htm, 2:1 method is sufficient for most purposes.

If I was trying this, I would have probably put down all the cans, them swept sand into the voids to distribute pressure. It may also have worked to use some sort of a fabric layer/mesh screen (geotextile? hardware cloth?) On top of the cans, and tacked down to wooden rounds on the edges to wooden rounds like Travis suggested.

Thanks for sharing the project! It never would have occurred to me to ue tin cans in a cob floor, and now I really want to try it and make it work :)

Sand is a good idea for filling in the voids between the cans, and I am sure that if you put a thick enough layer of cob over top the cans in the first place you wont have any problems. I would say 3 or 4 inches would be sufficient.