alternative foundations and flooring

So Glen,

How are your results so far with using the 5% portland in cob? Is it way too early to tell anything?

Where you are, maybe it never gets hot enough for the wax to melt on your cob. Where i am it gets hot in the summers
and i fear that the wax would 'creep' down when it gets hot. I don't know about the CO2 being absorbed by the lime.
I've heard that before, but never studied it...

Do you think the hydrated lime and sand are best used alone as mortar or do you add a bit of portland in the mix too?

hi rorie,do not add portland,it is not needed and counters many of the benifits of lime mortar.Wikipedia lime mortar,it's give a pretty good overview.

glen

OK Glen thanks,

I'd appreciate it if you let me know how the cob with portland turns out.

Ronie,
The reason most people don't use portland in their exterior plaster is that it doesn't breathe as a lime plaster will.  You can end up with trapped moisture and then mold. 

As to my stone wall, I do worry about the thermal transfer.  I am thinking of using foam board  or rock wool panels on the interior side of the wall to help with that.  I don't plan to do the round wall, but rather slight offset toward the hill to stabilize it against the backfill.  Back wall will only be about 4ft tall, and the slope is not steep.  It will not have slipform on top.  Tire wall will be uphill wall with french drain and gravel.  How does the overall plan sound to you? Or anyone else?--K

Keithbein,

Thanks for the info on the portland. My thoughts on using cement around the base of a structure is that it might help keep the weather from eroding the cob as quickly. Maybe cement could be used low then use lime farther up.

I hope you keep posting with pics and updates as to how your project goes.

Ronie, I hope the foundation will keep the cob high enough to keep weather off.  That and big overhangs.  I would still like to get some more feedback on my foundation plans, so I may start a new thread another time.  Progress will be slow for sure, but I am charting progress on my b l o g.  newenglandroad.blogspot.com  hoping to break ground this spring  Thanks for your comments and advice--K

Hi Keith,if you don't mind i will chime in here.I'm not a big fan of rammed tire walls if your building stone or cob on top.I see an issue with properly ramming the soil in the tire to create a solid enough base to carry the weight of stone or cob.If you don't compact it enough I see a lot of settling and cracking occurring.Infact,I can't see how one could compact the tires enough that you would not get stretching(tires) and or settling??.Keith,I didn't get were you were building.In a dry desert area is on thing,in an area where you are compacting with a moist soil is another.

glen

Has anyone here any first hand experience with insulation placed horizontally out from the foundation so the foundations need only be inches instead of feet high?
http://oikos.com/esb/43/foundations.html  I haven't seen anyone use it around here but it's apparently standard practice in Europe and I am wondering why people don't use it here.

I have no first hand experience with the technique but do know of a few homes built using the technique. It works. Why is it not used more here in the USA. I believe some of the reason is contractor inertia. It is a radical idea when everything you've been taught is to place the foundation footing below frost level. It can even save construction dollars. The extensive use of foam maybe discourage some folks, but it saves on a klot of concrete in many places. Maybe it's a trade off between the two.

Frost protected shallow foundations only work for buildings that are heated though. If unheated eventually the temperatures fall to below freezing.

If the insulation went all the way under the building, ground heat would be trapped underneath, and it would stay at that temperature (about 45° around here) and never freeze, even if the building were unheated. 

Dan

So you could theoretically simply lay a  whack of insulation panels on ground raised enough to keep dry, and just build on that for a heated building, as long as the insulation winged out about 8 feet on all sides from the outside wall? Then simply add dirt over top of the insulation outside the walls...Sort of like a mulched raised bed for your house 

I suppose keeping  the ground dry would be quite important.. moisture seems to cause most of the  problems.  Would there be any point in wrapping the insulation in recycled tarps (to help shed moisture and to help protect it from sharp pointy objects like rocks, or from moving if someone unthinkingly drives over it and breaks the panels!) ?

No Pam, not raised. 

Prepare your slab pour site by installing good drainage, leveling the site, and compacting any disturbed soil.  Form the edge area as appropriate; This area is often thickened for extra strength.  Lay down insulation panels and tape the seams.  Install rebar.  Pour the slab.

Forget the old tarps.  Keep the ground dry with good drainage.  Keep the slab dry by taping the seams of the insulation.  The insulation itself (extruded polystyrene) is quite impermeable to water.  Keep morons with motor vehicles away from your building site.  Make anyone who "unthinkingly drives over it" pay for repairs.  The pour prep should leave the ground flat, level, and smooth enough that panels on the ground can be walked on with no damage.

Put the insulation out to the side the same distance as your design frost depth, sloped slightly for drainage away from the slab.  Bury the insulation well, and beware of stupid people with big shovels planting things next to the house and damaging the insulation.  (Foundation plantings are generally a bad idea.)  Your insulation at least should be R-1 per foot design frost depth, meaning most places can use 1" R-5 insulation, but very cold areas might use 2". 

Dan

Huisjen was posting while I was typing/thinking. All good info by him.  Here in the high desert of NM everybody uses r10 even though we have a shallow frost depth. It makes for a very comfortable warm floor even without radiant heat embedded.


The insulation skirt around the perimeter should be as wide as the frost depth, for a rule of thumb. R-value of R-10 or better. The same R=value foam is used under the floor slab.

If ground water is a problem then the ground water needs to be drained. A french drain (perforated pipe) is normally used at the level of the footing. This needs to have an outlet, something that can be a problem if on flat land.  Most often FPSF are used when building on a  concrete slab. No reason the technique could not be transfered to cob or other earthen floors.

There are slightly different techniques applied to unheated buildings. Both are covered in the following download
http://www.toolbase.org/PDF/DesignGuides/revisedFPSFguide.pdf

Google should find other info as well.

Great info and a very detailed link.  I was a bit surprised at the illustrations in the link all showed the insulation installed flat as my understanding was that it should be sloped away from the house to facilitate water being diverted away. Since they make the point about drainage being very important that seems as though it might just be a missed edit.

I got interested in this when a round hay bale that had been unloaded in February got moved in late August and there was still ice under the centre foot or so. It called into question the need for a 5-6 foot foundation, I thought, though I haven't moved a bale in Feb that was put there in August to see if it works equally well the other way around! This could make building a small house in this area MUCH cheaper and at least as comfortable. 

Thanks again Huisjen and Don.  Great info!

Glen
I appreciate your comments greatly.  I am building in NW Ga which is fairly wet and humid, at times.  My soil has a good clay content and I think it will compact well.  The slipform foundation wall should act as a bond beam and keep any additional compaction even.  Also, the slipform technique should allow for even settling between courses so there is not a dramatic shift you could get from a poured wall compacting all at once.  The foundation wall will carry about a 5-6 foot cob infill wall as well as the timberframe posts, so it will be bearing a lot of weight down to the tires. 
Do you have  any personal experience with rammed tire foundations?  Or with cob or stone in conjunction with them, or do you just have  hunch about it?  I haven't been able to find much at all in support or against the idea, but would really like to get some good advice either way.  Also, what is your alternative to the tire foundation?  I am really trying to avoid the expense and eco-footprint of a standard poured concrete footing.  Thanks in advance for all your comments--K

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Hi Keith,if you don't mind i will chime in here.I'm not a big fan of rammed tire walls if your building stone or cob on top.I see an issue with properly ramming the soil in the tire to create a solid enough base to carry the weight of stone or cob.If you don't compact it enough I see a lot of settling and cracking occurring.Infact,I can't see how one could compact the tires enough that you would not get stretching(tires) and or settling??.Keith,I didn't get were you were building.In a dry desert area is on thing,in an area where you are compacting with a moist soil is another.

glen

Hey XUL, it seem everyone went off on a tangent about concrete. Some options for foundations (depending on where you live) 1) frost protected shallow foundation, drastically less concrete usage than a conventional stem wall, less digging and code approved ta-boot. 2) A rubble trench is a great option, (it you need to talk to a building inspector it's called "engineered fill" trench) That is a someone already responded is a 2' x 2' trench with 1.5" to 3" rubble in it. Anything will work, rock, brick, broken china, glass your name, as long as it wont break down. The drain tile goes in the bottom of the trench and make sure to compact the fill before putting the bond beam on top. The bond beam is what your walls will actually sit on. It can be urbanite (recycled concrete) or you can pour virgin concrete, and there are also earth bags.  A combination of the two listed above is a frost protected engineered fill trench. This is a engineered fill trench that has 2" rigid foam around the outside of the foundation. (This is the foundation I'm using for a load-bearing BaleCob cabin I'm building this summer.) And with an engineers stamp it will pass code.  Hope this helps.  Cheers

Yes Pangea, I agree this thread did wander a bit.  Thanks for your comments about foundations.  The trench would be less work than rammed tires, though I am not convinced that would be a bad idea.  Since I am planning a slipform stem wall, I could probably just build that right on top of the trench as it will act as a bond beam.  The wall will only be 30 in high and 18 in thick to support timberframing posts and about a 5ft cob wall up to the plate.  I do need a retaining wall on the north end of the home and I am still planning to do a tire wall there.  Do you recommend the trench below that, or can I backfill with a couple feet of washed gravel with a drain tile in the bottom as I was planning? The retaining wall should be about 4 ft high and will weigh enough to keep it stable.  I plan to put a bond beam atop that and it will also support timberframe posts and a shorter cob wall to the plate.  I am gathering info, so I appreciate any thoughts you have on my project.  --K


Hey XUL, it seem everyone went off on a tangent about concrete. Some options for foundations (depending on where you live) 1) frost protected shallow foundation, drastically less concrete usage than a conventional stem wall, less digging and code approved ta-boot. 2) A rubble trench is a great option, (it you need to talk to a building inspector it's called "engineered fill" trench) That is a someone already responded is a 2' x 2' trench with 1.5" to 3" rubble in it. Anything will work, rock, brick, broken china, glass your name, as long as it wont break down. The drain tile goes in the bottom of the trench and make sure to compact the fill before putting the bond beam on top. The bond beam is what your walls will actually sit on. It can be urbanite (recycled concrete) or you can pour virgin concrete, and there are also earth bags.  A combination of the two listed above is a frost protected engineered fill trench. This is a engineered fill trench that has 2" rigid foam around the outside of the foundation. (This is the foundation I'm using for a load-bearing BaleCob cabin I'm building this summer.) And with an engineers stamp it will pass code.  Hope this helps.  Cheers

the old Strawbale list had extensive discussion on alternate flooring. I recall some about hardened dirt floor that was supposed to have worked fairly well.

I'm not sure if they are still around but a google should turn up something.

Bob Durtschi

solomon martin wrote:Here is a method that may be less labor intensive than a full stone or concrete foundation: build a series of masonry (stone) piers that will support your floor beams at 8 or 10ft. intervals.  In between the piers, hang expanded metal lathe and coat with mortar to make a 1/2 inch thick ferrous cement "foundation" walls.  You are still using cement, but only a fraction compared to a concrete stem wall.  You can increase the insulation factor by applying cob or something to the interior of the ferrous cement.

I'm planning to do something similar (or identical, if I understand your description) to what you wrote here. I will be using concrete piers, with copious rebar to span the piers, laying mesh over that, and troweling concrete into the mesh. I will probably have several layers of mesh to make for a durable floor. I'm interested in keeping lumber usage to a minimum.

Any additional clarification about your post would be useful---

While this thread may be a few months old, I am very interested in learning more from it.

I'm contemplating building a greenhouse and shed from reclaimed materials. I"m looking at the foundation at the moment and it appears I'd need +/-half a yard of concrete. The conventional wisdom has me teetering between an electric mixer, or having a concrete truck come out. Though I prefer to do it myself, neither seem financially ideal.

Stephen Lloyd wrote:

solomon martin wrote:Here is a method that may be less labor intensive than a full stone or concrete foundation: build a series of masonry (stone) piers that will support your floor beams at 8 or 10ft. intervals.  In between the piers, hang expanded metal lathe and coat with mortar to make a 1/2 inch thick ferrous cement "foundation" walls.  You are still using cement, but only a fraction compared to a concrete stem wall.  You can increase the insulation factor by applying cob or something to the interior of the ferrous cement.

I'm planning to do something similar (or identical, if I understand your description) to what you wrote here. I will be using concrete piers, with copious rebar to span the piers, laying mesh over that, and troweling concrete into the mesh. I will probably have several layers of mesh to make for a durable floor. I'm interested in keeping lumber usage to a minimum.

Any additional clarification about your post would be useful---

I guess the discussion of a "better" foundation puzzles me. If you have access to a road (which I presume you do), the best foundation is sand, gravel, and concrete. Excavate to a solid base, backfill with good non-frost susceptible material, build high, and use concrete. Concrete is amazing stuff. It lasts FOREVER. REinforced concrete is amazingly flexible. It's impermeable. It's hard. It's clean. You can incorporate it into an excellent thermal mass. You can shape it any way you like. It's beautiful. I'll take a good concrete foundation any day. Protect your building investment with a good foundation. Do it once, do it right, and get 'er done!

Steve Cinelli wrote: Excavate to a solid base, backfill with good non-frost susceptible material, build high, and use concrete. Concrete is amazing stuff. It lasts FOREVER. REinforced concrete is amazingly flexible. It's impermeable. It's hard. It's clean.

This thread is about alternative foundations and flooring, in the green building section of a permaculture forum. Reinforced concrete is neither 'green' or 'alternative'. We are looking for better ways.

I have a friend that makes a foundation that is basalt fiber poles that have augers on the end and they are sunk twenty feet down into the land. Everything is then attached to them like piers. He built one house in Colorado with this technique. I know there are a few other similar designs being made now by different companies. Most others use steel though.

He claims they will resist tornados. I have not seen the tests or anything so I can't verify personally.

Hello to all,  I am new to this way of communicating, so please forgive the occasional dumb question. Here in northern NSW, AU, my lady and I are building a two story, round-wood, post and beam, circular building (similar to a grain silo) with straw bale infill walls, clay/lime render skins and an earthen floor with PEX radiant heating and hardwood inlays. I am 40 years a painter and plasterer with a fair bit of construction knowledge. I also spent 30 years of my adult life in a religiously constricted, Judeo-Christian, share everything and own nothing community, which I departed about 5 years ago. It was a profoundly beautiful way of life in many ways, but having gained a sort of PhD in narrow-mindedness, I'm now like a kid in a candy store of new ideas and ways to embrace life. I too see that building a home is not rocket science and that we should look to ourselves first for answers, but having said that, good, sound advice is a lovely and comforting thing. We are also choosing to spend as little, and be as resourceful as humanly possible. And, sorry about the metric measurements; I'm originally from the U.S., but I've fallen in love with millimeters.
 
So... my concern is foundations. The site is gently sloping; the soil is sandy loam. I've carved out a flat pad with our farm tractor, digging into the high side and moving that soil to the lower side. I'm going to hire a plate compactor and pound the filled side for a loong time. The winters here are incredibly mild and frost is not an issue. I'm from Wisconsin where people have basements and central heating. Not here. Termites (white ants) are a definite problem though. Our 40 acres is largely regrowth Aussie hardwood, but lacking in the tallowoods and grey gums, etc... that one would chose to be near or in the ground. I see the sense in using concrete under buildings, but I'd really rather not, and we can't get a concrete truck down to the site anyway. We are on a creek with an endless supply of smooth river rock in all sizes. We also have an elegant stand of flooded gums (eucalyptus grandis), tall and straight as ships masts.  Fine for framing, floors and external features, but not durable in the ground. I want this building to be there in a hundred years, so I understand that I need to get down to stable soil for a start.
 
My idea is this:  Fire up my trusty earth auger and drill a series of 250mm wide holes around the perimeter at around 1200mm deep, maybe up to 2 meters deep on the lower, filled side. Fill the compacted bottom of each hole with 200mm of clean stone. Then weld a thick steel base plate onto the end of a galvanized, 100 x 100 x 4mm square hollow steel section. Being a painter, I would coat each SHS with many coats of serious anti-corrosion paint. Then place each one onto it's stony pad, level up and back-fill with more clean stone. These steel posts would protrude above ground level to the height of the coming grade beam. Then I plan to dig and fill a rubble trench between each of these in-ground posts. The top of that trench brings us up to grade. Then we lay 2 or 3 courses of rock-filled, barbed wire reinforced earth bags to form a grade beam. That done, I would bolt my heavily preserved, flooded gum posts onto standoff stirrups welded to the top of each steel pier. Then I would build a strong upper ring beam to lock the timber posts into position at the top. Back at the base, I would construct a timber, ladder-type stem wall for the straw bales to rest on. This would, of course, be bolted to the timber posts as well, tying it all together.  I would then go back to the top and construct the roof before installing the straw bale infill, etc...

In all I've read, I haven't seen this method described, and of course I ask myself why. Am I missing something? Or maybe it is fundamentally sound, but needs some help here and there. Any comment or ideas would be greatly appreciated.   Have a creative day....