basement for cob dwelling?

OK all you experts! I need to put my water collection tank indoors as we have subzero winters. I really do not want to build a whole room just for that and was wondering what your thoughts were on a stone basement 5' in the ground 2'above like stem walls are... If I do it with natural hydronic lime and sand or pumice, it should be sound for hundreds of years? Why are there no cob basements?
Suzanne Cornell

So you have a 30ft by 30ft dwelling.
And in the center of it you want to build some type of 20ft by 20ft hole in the ground that is 3ft deep (9,000 gal)
You want to coat that hole with a pond liner or waterproof cement.


The idea sounds very doable. How much water do you need to store?

If you haven't already built your dwelling. You could build a steel or cement room (11ft by 11ft by 10ft high aka 9,000 gal).
This room could be placed in the center of the building, and heat during the summer sent to it up to 70F and then extracted in the winter.

Infact heat the water during the winter and then use that thermal mass to heat the rest of the house.

I am trying to envision the house maybe a 3room by 3room house with the middle room being the water tank.
With a wrap around hallway/sunroom/porch on the outside of the dwelling.

S bengi,
I like your enthusiasm. I am trying to avoid making my house larger to accommodate the tank. I am trying to find out why one can or can not build a basement under a cob house. While your design sounds nice it in no way address my inquiry about basements.... Any one know about basements for a cob house?

Hi Suzanne Cornell,

The reason cobb is not employed for basement or fossorial dwelling walls in general, is the lack of tensile strength and "stand alone" tectonic resistance. Even an earthbag basement would be outside the strength requirements for such a below grade structure without some additional reinforcements in most cases.

Stone and brick are about your only "natural" options, which I love, however these leads us to "economy of effort" concerns. If may not be desired to build more above grade architecture for a project, yet the cost is often less both physically and fiscally that a "money pit." Basements are a vestigial architectural element of the "root cellar," for the most part, and now most contractors and clients only think they have to have one, or that it well be less than building above ground. Sometimes it may be...often, not so much.

Regards,

j

So...
S Benji, I dismissed you idea too soon it would seem, my apologies.
Jay-So building a basement of stone wide enough to hold cob, would be a huge time consuming effort? It would take longer the building a room of cob? Too bad I don't live with a stone mason. I was gonna pour a few inches of pumice below the structure to insulate and in-between the stone and the earth, thought I had it all figured out. Where I live we have an abundance of stones, I thought i'd be putting local resources to good use. The houses with basements around here tend to have warmer floors in the winter, they do however occasionally flood during spring thaw, when the snow melts quicker than the earth unfreezes, leading to unusual moment of surface water..which is why all of them have sump pumps. Also our frost line is at about 4' I would have to dig in 4.5' in any event to accommodate the drain, so why not just put a basement in if I have to dig that deep any way?Could I leave berms of earth inside the basement, to reduce the work, where loads would be above so I don't have to put Stone Walls every where I'm going to have a load.. rocket stove and bench, large bath tub, and a middle supporting wall, (because the second floor is only half the size of the first floor)?
Jay- in your estimation how much longer would it take?
S Benji, I am now seriously contemplating you idea... I have a collection tank right now, it holds 1,000 gallons. the idea of digging it in a few feet it intriguing, but it has a drain valve near the bottom.

So building a basement of stone wide enough to hold cob, would be a huge time consuming effort?

Basements in general, unless prefabbed and/or formed, are always gong to be more effort than a wood structure above grade. It is also a "skill set" related topic, as the more building skills (knowledge) one has, the easier it becomes. I would also suggest that if you build with stone the only cobb that would be needed would general be used for a traditional cobb mortar. If plastering is used that is consider a finish treatment and I would suggest lime over cob in that case. I don't like cobb in basements or below grade in most (not all) designs.

It would take longer the building a room of cob?

Yes, for the most part it would...and could be said that even 10 times more effort.

I was gonna pour a few inches of pumice below the structure to insulate and in-between the stone and the earth, thought I had it all figured out. Where I live we have an abundance of stones, I thought i'd be putting local resources to good use.

Stone would be great, and you can still do it. I love stone root cellars, it just is not, nor should it be considered a "simple task."

The houses with basements around here tend to have warmer floors in the winter, they do however occasionally flood during spring thaw, when the snow melts quicker than the earth unfreezes, leading to unusual moment of surface water..which is why all of them have sump pumps. Also our frost line is at about 4' I would have to dig in 4.5' in any event to accommodate the drain, so why not just put a basement in if I have to dig that deep any way?

First, "frost heave," and "frost lines" are very loosely bantered words that folks through around without a complete understanding of them. If you have a heavy clay soil that saturates and holds water, then there can be real issues...even more so if bentonite clays are present. However, if proper drainage and gravel-stone are used for a foundation and related fossorial elements of a structure then this is a "none topic" as there will be no flooding or related issues unless the architecture is on the side of a lake or river that overruns its banks.

Could I leave berms of earth inside the basement, to reduce the work, where loads would be above so I don't have to put Stone Walls every where I'm going to have a load.. rocket stove and bench, large bath tub, and a middle supporting wall, (because the second floor is only half the size of the first floor)?

Hmmm...??..."berms" in the root cellar? I must not be understanding this? It doesn't sound like a plausible design to me, but I don't think I have the same image in my head as you may have...

Jay- in your estimation how much longer would it take?

Minimum 2x and as much as 10x depending on the design matrix and acquired skill sets and tools.

Regards,

j

No worries.

If your 'basement' is bigger than the plastic water tank that you are putting it in. Then you should have space to attach a pump to the drain hole. If you ever need to drain said 'plastic water tank' then turn on the pump and discharge via a really long pipe to daylight outside. Sure it might kill your $200 pump. But if you only drain every 5 years and it takes 2 drains to kill your pump that really isn't alot of money. You will probably end up spending $2000 to drain your sewer ever 10years vs the $200 for the pump.

Basements in general, unless prefabbed and/or formed, are always gong to be more effort than a wood structure above grade. It is also a "skill set" related topic, as the more building skills (knowledge) one has, the easier it becomes. I would also suggest that if you build with stone the only cobb that would be needed would general be used for a traditional cobb mortar. If plastering is used that is consider a finish treatment and I would suggest lime over cob in that case. I don't like cobb in basements or below grade in most (not all) designs.

Jay, I agree I would never put cob in a basement. Just rocks and mortar. It makes sense that it would be more effort than a wooden structure, but more effort than a room of cob? when I am actually doubling the size of the house... Well I guess it could take more effort, (Can you tell i'm a little stubborn?)I'm having a hard time letting go of the desire to put a basement in. I'll have to redo all my plains...
I never thought it would be simple, I've been experimenting with small batches of cob, and reading everything on the subject I can get my hands on for 4 years now, I am finally ready to "dig" in. Also I have had disasters related to water storage, and pipes in badly built conventional homes and I am determined to have everything "tucked" away where 20 below winds can't freeze my pipes and I have alternatives for heat. Rocket stove and solar floor heat/ backed up by small propane just incase.( I think I know what I am getting into.) As my grandmother said "anything worth doing is worth doing right" I am determined to do it well and right, if it takes longer thats OK. I am blessed with living in the country where many of my neighbors have a diverse skill set, masonry, tractor engines, carpentry and plumbing..There very pleasant at offering good advice, and will stop me if I am doing something "wrong".
BUT having said all the reason I want to do it.. I guess I will build a chicken coop with a basement first, see how that goes and then decide. (Just a little stubborn) What will the chickens do with a basement I wonder..they like to go up...not down.....perhaps a small room that can be attached to the house later, is a better idea.
As to frost lines.. my neighbor just had to put in a telephone pole and he dug down 4' before he found unfrozen ground, is that not the frost line?

Suzanne

Wouldn't building your house over a well, make more sense.

Instead of digging out a basement for your entire house, you could put your house on 6 or 9 telephone pole. These pole would only stick above to ground by about 3ft in case of floods or something. Then way you would only have to dig out a few holes vs an entire basement.

If you were skilled enough you could even put your house on some 'huge stones....small boulders' and use those as the poles.

But if you really must play with cob, I like your idea of building a cob barn/chicken house.

S Benji,
LOL!!
it probably would make more sense to build it over a well!
I love the idea of a house on boulders...but it is too cold here in the winter for that not to increase heating costs. I plan on using my neighbor and his front end loader to dig my basement. I think digging with a shovel would kill me. The water quality is not good in the water table here. So I am going to collect rain water-in the tank- under my house- in the basement. How is that for stubborn? As a large experiment, I am going to try and build just a part of the house (one room) with a basement big enough for the water tank and me to walk around it and plum it.If it all goes well, I will do the rest of the house that way, and if it doesn't I will have my water storage under part of the house and the rest of it done without a basement. Thats my decision at least for today.. things are always changing..
Suzanne

Hi Suzanne,

I am about to write here almost verbatim what I have written before and again on another post just tonight...

I have been in, out, and around the architectural field for over 40 years now...I have watch many things develop and undermine good building habits of the past. I can begin to write about the never ending drive of industry to make profit and the human drive to "reinvent." Sometimes great things comes of this...unfortunately, most is not, and some is actually just plain bad...I see most designs of modernity preparing humans for living in space as humans seem to bifurcate socially as a species with some only feeling comfortable in the country, while others are much more secure packed in shoulder to shoulder, wrapped in plastic, glass, concrete and steel. I am sure that when the time comes, we will launch a new age for our species as we reach for the stars...but...until then most of what we build today is but a glimmer of what our forbears achieved.

With that said, I would suggest to always look first to the vernacular architecture of a region that has centuries, if not millenia, behind application in good use. The modern basement is a poor interpretation of a well built and structure root cellar more often outside the house than allways under it. I would also humbly suggest that desire, drive, motivation and stubbornness can be powerful tools...These characteristics can also push folks in directions they ought not go. I watch in this current trend of "natural" and "new age" building with many wonderful..."ideas and concepts," but I must share that most folks have more drive and motivation than common sense and the necessary traditional building skill sets they should have to achieve what the "think" is a good idea. What I typically do with clients and students is ask a series of questions...if they can't answer those questions then it is most likely they are not ready to tackle whatever it is we may be discussing at that given time. In this case, the fundamental elements sound acceptable, and there has been great effort to learn as much as possible about a given modality of building...such as cobb. However, when we get too close to a subject modality, romance for the method often blinds us to better options.

I love the idea of a house on boulders...but it is too cold here in the winter for that not to increase heating costs.

I live in Vermont and travel all across this country...I am not sure I have seen very many regions that get colder on average than what we see here in New England, and even in places that do, stone plinth architecture as S Bengi suggested is very common and in good order of application. There really isn't such a thing as "too cold" if a vernacula method of application for the stone is correctly facilitated in the system. Whether building on a raise podii of earth and stone or other similar systems, structures with a "crawl space" foundation can be very warm if designed and built well.

As for putting a well under a house...this is generally a very bad idea unless the well is spring fed and hand dug for easy servicing. If it is a modern "drilled well" you have not place one of you most expensive assets over another rendering servicing it almost impossible. There is a principle rule in good design (there are several of course) and that is serviceability, serviceability, serviceability...and if a design does not have it...it is generally not a good design...

Without knowing the finer details, location, actual skill sets and tools available, it is hard to really make a complete evaluation and sound advice there of. It sounds like there is a rough plan, and if more work is required to achieve it over other methods that is acceptable. I only warn against such notions as frugality and efficiency of employed means, methods and materials was a path of wisdom our ancestors seemed to follow when building their architecture which they did much better than we do today...

Regards,

j

J,
I assumed that S was joking, referring to the trouble I was going through to build. Sorry if you thought I was actually thinking of putting a well in my basement. I want a cellar, a walk out cellar because I do not want to store hundreds of gallons of collected rain water in a cob room, and I prefer my laundry piles out of my living space, and I need a place for my batteries, and solar equipment. Seems that all that stuff is best put in a basement, as it is too cold here in the winter to have an outside shed for them. I am willing to put in the time and effort for the basement, properly done with a pazzolian mortar I think it will last a long time, and I look forward to learning and conversing with the grandmothers as I place them in a wall that my son and his decedents will touch and live with. This makes me happy. We will see in the doing how hard I find it, but I think it is not too much more effort to do a basement than laying a 4.5' deep foundation ditch as that seems to be our new frost line.
As for boulders, I can lift rocks, I can not move boulders, and there are not many easily attained boulders around here but there are plenty of biggish rocks, so no boulders, but easily accessible pipes and electric panels.
regards

Hi Suzanne,

I don't really care for basements in general, so I should (if I had not) share that subjective bias...

With that said...I love walkcellars!! To layfolk that may seem like a paradox, but for experience designers/builders...it makes sense. They are actually a serviceable form of the modern "basement." Just like in "bank barns" the topography of the building site is put to good use.

I want a cellar, a walk out cellar because I do not want to store hundreds of gallons of collected rain water in a cob room, and I prefer my laundry piles out of my living space, and I need a place for my batteries, and solar equipment. Seems that all that stuff is best put in a basement...

O.K. some of that works, some perhaps not:

1. Water stored inside the thermal envelope must be in well sealed vessels or tanks, otherwise too much humidity is brought in and seldom managed properly. With that said, in the correct form/type of architecture I have seen several spring fed streams flow under old stone and timber houses for hundreds of years with little ill effect until "modern materials" and "sealing methods" caused moisture build up within these ancient cellars.

2. I strongly discourage solar and batteries storage within or near a living space. Yes it is often done, and some even recommend it. There is too great a risk of explosions, unknown or wanted gas releases, and other fire hazards. Many insurance companies insist on a "battery bank house" separate from other buildings and some areas insist on either fire suppression systems or at minimum appropriate fire extinguishers present. I have three neighbors here in Vermont within 6 miles of me that I know of off the top of head that are all "off grid" and have solar,wind, and/or hydro. All have separate buildings for batteries or have switch to a "sell back" program with local utilities. If there is a "battery bank" within the living space...fireproof it, vent it, and understand well the risks...

I love your enthusiasm for stone and proper natural mortars. There are many formula and methods to consider whether using clay brick, or some form of stone. I tend to lay stone in the "Asian" format of "herringbone" as it drains water better and gets "tighter" over time, unlike "ashlar" modalities which can slip, slide and shift over time...even with mortars.

No one (or at least normal folk) can "move boulders" alone, nor can many even move most rocks efficiently. Stone work is about "leverage" and "mechanical advantage." You will learn the use of block and tackle, chain hoists, ramps, lever bars, wedges, and related as you move into stone work, as well as the "jigsaw" of stone puzzling, which comes with splitting and shaping where need be. Big stones tie things together and make for stronger walls. So please don't make the mistake too many novice make and build a "cobble stone wall." These are for aesthetics...Not structural durability and long service.

If the site is prepped correctly for good drainage "to light"...forest (unless you have permafrost?) is never an issue. This has become a "modern myth" of ignorance in understanding traditional building systems. If there is not water, there is no frost heave. Bentonite clays in a building site are much more of a concern as these expand with water more than ice, and the two combined can literally split a mountain in half...and have.

Regards,

j

J
I strongly agree with you about.. well most things, but specifically to this post, I agree about walk out cellars. I am currently living in an old farm house with a basement with horrible access.. there is an old furnace down there that i am going to have to dismantle to get out!! augh!
I have a (eek) plastic potable water tank designed for holding water tight! until my soldering gets better and I learn how to make or come across copper one,or win the lottery and buy one, its going to be the only plastic thing in the house. I hate plastic.
I have a box I had built to my specifications with vents medium low and a chimney vent with a vent fan up high and a very tight lid for my batteries. Safety first, I don't want to breath the out-gasses. I'm pretty sure I can matin them without causing a fire, but thank you sincerely for your concern.
I have a chain hoist and a lever bar, and I forget what they are called.... a rock hammer? For making thing fit, And an abundance of Rocks of every size, I look forward to the puzzle. I work with people all day and they puzzle me the most, I look forward to one I can hopefully solve. I know I 'll need strong canvas to lug/
drag some rocks, and many gloves, I have the knee pads and good boots.and I have to get a kidney belt. am I forgetting anything?
The frost line doesn't matter? I JUST NOW understand your saying I don't need a cellar... OK, duh! But here is the thing, I t will look great, and it will be a walk out. I think stone and cob are so beautiful together. Do you think it is a misuse of resources? will I be disturbing nature too much by using them for my cellar instead of leaving them where they are?
Did I say I redid my design to be 15x20 on the inside.. I guess that 20x 25 on the outside..I was trying to make it sound small.

Hi Suzanne...

I have a (eek) plastic potable water tank designed for holding water tight! until my soldering gets better and I learn how to make or come across copper one,or win the lottery and buy one, its going to be the only plastic thing in the house. I hate plastic.

If you want a nice tank for water, you could always carve one from a big stone...I'm only kind of making a joke as it isn't as hard as you may think. Its actually a lot easier than moving the silly things once you have created them. The larges I have done is about the size of an average two person tube.

Another type that is nice to make is wood, and these are probably the easiest of natural ones to make...I keep metal for cooking kettles and cauldrons or tools.

The last type is a bit harder than the wood to fashion properly, but not as hard (pun intended...) as the stone. That is ones made of cobb and lined with a harder version of Tadelakt to water proof it.

I have a box I had built to my specifications with vents medium low and a chimney vent with a vent fan up high and a very tight lid for my batteries.

Perfect...that is excellent and means you have thought about this...I am relieved and need to say no more...

I have a chain hoist and a lever bar, and I forget what they are called.... a rock hammer? For making thing fit, And an abundance of Rocks of every size, I look forward to the puzzle. I work with people all day and they puzzle me the most, I look forward to one I can hopefully solve.

Warning!!...in just a few hours, or perhaps days...you will know how you "really feel," about stone. The bad part about the mysteries and puzzle that is "stone." It can capture your soul like no other medium. I have spent a life in love with the stuff, from carving it, to climbing 1000 meter cliffs, and studying its many forms...this stuff is just magical...I have a feeling you will really love it...

Here is a link and a person that you may find inspiring...She is just a grand person...Thea Alvin.

If the bond is there, that I think you will have, gloves will go away soon, or at least most of the time. It gets between you and the rock, which just needs to be touched to bare skin...same as clay.

More than tarps, a good "Dolly Cart" will do more work than just about any other "moving tool."

...am I forgetting anything?

Oh yes...lots and lots of stuff, but the stone will probably teach you more than my "babbling" and you can always reach out should you have more questions or need guidance..

I would suggest talking to my Dear friends at Trow and Holden, as this is where all "good stone people" get there tools. One of my 3lb hammers I use in timber framing and stone carving to strike my many chisels is over 100 years old and was forged in the Smithery of Trow and Holden. You may find this Permies link of interest to read: Basic Set of Stone Tools

The frost line doesn't matter? I JUST NOW understand your saying I don't need a cellar...

Gosh, sorry...that's not what I meant...If you want a walk out Cellar, by all means build one. I am saying "depth" is only as important as you want to make it...Don't worry about frost heave. If you build it properly with good and well done drainage, there can not be any heave as there won't be any clay or water to cause it. You may now not have to go so deep into the ground either, but you will have to either bring in gravel or lay lots of little drain stone...and I mean metric tons worth. Don't let that frighten you though as the average mason on an average day moves cumulatively as much as 10 to 20 tons of stone...We be a different breed of human... Thea from above probably doubles that on some days...

I think stone and cob are so beautiful together. Do you think it is a misuse of resources? will I be disturbing nature too much by using them for my cellar instead of leaving them where they are?
Did I say I redid my design to be 15x20 on the inside.. I guess that 20x 25 on the outside..I was trying to make it sound small.

Stones are to my people and many other indigenous people sacred. That does not mean you can not touch, move or even change them. It does mean you have to ecknowledge that they are a gift, and have there own existence beyond "human whims" for them or our general hubris. Stone and cobb can work very well together if done properly, and I see no issue with that at all. The first mortars were simple cobb mortars... not lime...and NEVER concrete or anything with "portland" in it.

The size sounds wonderful, for a first time builder, and I would love to see pictures of the building site. Please let us all know your progress and other ideas.

Regards,

j