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Kane Jamison
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Location: West Seattle, WA
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Any of you that read Yes! Magazine might remember an issue from last fall with a Cob house on the front.  Here's the article: http://www.yesmagazine.org/issues/a-resilient-community/a-hand-built-home

Anyways, looks like he's having mold issues right now from a blog post he put up:

Quoted from http://small-scale.net/yearofmud/2011/02/14/mold-has-reared-its-ugly-head-winter-moisture-issues/ :
Mold has reared its ugly, ugly head in my home, and I have recently been consumed with attempting to determine a solution to this problem. I ask readers (especially those with experience living in cob houses in cold climates!) to please read ahead and help me to determine the best course of action. Any advice would be dearly appreciated.

Here are all the details fit to print.


I live in northeastern Missouri, where temperatures can get to below 0º. This winter, we’ve had perhaps four below 0º nights thus far. But typically, our winter lows are in the high teens or 20s, with daytime temps. in the 20s or 30s. My house is all cob, with 18″ thick walls. There is no insulation in the floor, foundation, or roof (other than the soil). (I will never build like that again in this climate…!)

I am having  a very big mold/mildew problem on the bottom 15% of the interior walls, particularly on the west and north walls. The walls register as low as 38º towards the bottom of the wall, and the foundation about the same in the mornings. Higher up (at head height) the temperature reads in the mid 50s, and even higher it reads in the 60s. (I tested the wall temperatures with an infrared temperature sensor.)

I believe it is condensation that collects on the face of the cold urbanite foundation and the coldest bottom part of the wall (because of the big temperature difference between that part of the wall and the air inside), and then molds from not being able to dry quickly. Condensation is so great in places that the floor is damp in spots, too. We’ve got the small Morso wood stove and can get the house to about 70º, but most of the walls remain quite cool, of course, even after a day of heat.

Furniture close to the walls on the west and north is also a concern, since airflow is not as great with the bed against the wall, for example.

The mold appears as white fuzz, but in some rare places it is a green mold if I have not been over it with vinegar for some time. The regular task of moving furniture to spray the walls with vinegar to kill the mold is tedious and tiresome. The colder it gets, the worse the problem. I have reason to believe that April”s recent health problems (allergic attacks in the form of swollen lips and eyes) have been the direct result of this moldly living environment, as well, which is a huge concern for us, and more than enough reasons to solve this problem as soon as possible.

My current line of thought is that I must insulate the bottom part of the wall and/or foundation. I imagine it would be better to insulate on the exterior, but all I can imagine is having to build a kind of extended foundation and then somehow build basically another wall (or tapered wall) to insulated the coldest parts of the cob. But with light clay straw or straw bales, I am not sure.

I also wonder about the effectiveness of lime plaster in this situation. Would covering the lower 1/4 of my interior wall in a lime plaster or lime wash prevent mold from developing on the surface of the wall? Would moisture simply condense on the surface, and could I then wipe the lime with a rag if it’s bad enough? Obviously lime plaster would not stop the wall from condensing, but it could stop mold from developing since it is antifungal, I think.

Additionally, we are considering an insulated bale-cob addition on the north of the house for insulating that coldest north wall, but the west wall would still be unprotected and need some kind of insulation.

A greenhouse addition could help to maintain higher indoor temperatures (on sunny days, anyway), but it would doubtful have a big impact on condensation development.

Any advice would be dearly appreciated. I fear my girlfriend’s health is at risk it we continue to live in this environment without resolving the moisture issues.

Also, it is important to note that the humidity is always very high, even in the winter. (Right now it’s around 65% and it can even get higher!) Perhaps we need better ventilation…


Probably worth a read for anyone in the process of designing their summer building plans right now... 
 
Jami McBride
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In the olden days, in rainy, damp England they used lime wash - said to really kill everything.

It is his foundation which is causing his problems, and not the cob.  He needs a moisture barrier between the ground and his house.  I don't know how he could achieve this now though.  I don't think insulating will help at this point.  Cob will allow some moisture to pass out of the walls as long as it isn't to overwhelming. 
 
Jonathan 'yukkuri' Kame
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Location: Foothills north of L.A., zone 9ish mediterranean
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Jami McBride wrote:
It is his foundation which is causing his problems, and not the cob.  He needs a moisture barrier between the ground and his house.  I don't know how he could achieve this now though.  I don't think insulating will help at this point.  Cob will allow some moisture to pass out of the walls as long as it isn't to overwhelming. 



Yes, it sounds like the foundation to me.  The old saying about cob is the house needs good boots and a good hat... in this case, bad boots.   The urbanite may be wicking moisture up to the cob, or it may be coming through the earthen floor, and then condensing on the walls. Living roofs, unless done properly, often end up having leakage issues leading to mold.  

Assuming the moisture is coming from below, I imagine it would be at least helpful to create an waterproof umbrella of some sort draining all moisture as far away from the building as possible, so the moisture content of the earth will be much lower below the building.  

Mold can be LIFE THREATENING, and fungal infections in the body can last for years and lead to all sorts of health problems.  Doug Kaufman is one of the better educators on this topic: http://www.knowthecause.com/

The house is not fit to live in until the mold issue is resolved.  

A dehumidifier is one of the most effective tools in fighting mold.  The coils will be colder than the walls, and a fan pulls the air through, so water condenses on the coils rather than the walls.  It will also warm the air, so it can hold more water (that gets pulled out through the coils.)  

An ozone machine will also kill mold, but the effect on humans is controversial, so it should only be run when humans are out of the house.  

Chlorine Dioxide, aka vital oxide is supposed to be one of the safest chemicals for fighting mold. Approved for food surfaces without washing by the EPA so fairly low toxicity for humans. People actually take it internally in the Miracle Mineral Supplement, though the FDA does not approve.  It is basically a bleach, but far less toxic than ordinary chlorox, or the mold, for that matter.  Should be able to pick it up at home depot.  

Poor folks put a lot of work into that cob house, shame it isn't working out as they had hoped.  
 
Jami McBride
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Food Grade 35% Hydrogen Peroxide (deluded down to 3% with distilled water) is also good to inhale and take internally when exposed to mold.  Cheep HP would work on the walls too, but not any better than white vinegar. 

The dehumidifier in the house would help greatly.  As well as, digging a trench outside to carry away the water from the roof and surrounding soil as fast a possible. 

It might be less work to keep a spray bottle of vinegar and spray the walls daily instead of cleaning them by hand.

This is a shame . . .
 
Neal McSpadden
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Isn't there a thread somewhere on installing french drains around houses?
 
Jami McBride
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Yes there is, but there is a lot to french drains (expense and labor) and they require a bit of expertise to be done right, and time to do all the construction.  An ugly trench will be the down-and-dirty, right now, way to move water away from the house.  I know what I am talking about, having had to dig my own on a couple of occasions to stop flooding into my house. 

 
Mekka Pakanohida
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Location: Zone 9 - Coastal Oregon
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tamo42 wrote:
Isn't there a thread somewhere on installing french drains around houses?


Every book on cobbing I have read explains how to make them and how important that step is for making a cob building.  The foundation and the drain area around it is of primary importance and is certainly not an area to be skipped on with time, money or labor.

Just IMO...  no offense.
 
                                
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Location: Saluda, NC
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This should help.  Glen is on this site some and he might stop in.  Read through his posts.

http://countryplans.com/smf/index.php?topic=9956.0
 
Scott Howard
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I always say (and I come from the moldiest place on earth)
use borax liberally.  It is water soluable, so you can spray it on.  I buy the 10 molar (concentrated) kind.  It's non-toxic, eco-friendly, simple to refine and use, and not expensive.
 
Matt River
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I think the issue is not an incorrect foundation installation if the author/builder stated things correctly. Very cold walls can condensate internally to the home - human and pet breathing as well as cooking makes a lot of humidity. A recent job for me was digging out around a home that was never backfilled correctly, applying 2" foam, stucco, and culture stone, and fixing the grading aroun the home. Previous to my work, the walls in the basement were getting tons of condensate, dripping, and eventually this formed black mold on the tops of the walls. The scarier issue with cob is internal mold due to the clay matrix absorbing and internalizing the inside condensate. An application of a tile baseboard or wainscoat would create an impermeable membrane against the condensate, but would not stop it.
 
Neal Mike
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Mold is a serious issue. Even a small water leak or moisture causes mold to appear. You cannot pay attention all the time at every corner of your house but you need to be careful in this case as molds can cause many health problems and allergies.
 
Brittany Smith
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How can someone avoid such stated situation when building a cob home? It seems that cob has successfully been built in damp England, incredible cob homes in cold cold Canada...so why would this structure not be suited for NE Missouri? Can anyone bring light to this question? I see people mention a dehumidifier, but having one running all the time seems like it would be a bit much..? Are there other ways?
 
Brian Knight
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There are many problem situations stated in the thread and many ways for dealing with them. My recent blog outlines the 3 main ways water and moisture destroys our homes and buildings which would include cob of course.

http://wncgreenblogcollective.wordpress.com/2013/12/29/the-top-3-ways-that-water-destroys-our-homes-and-buildings/

I think the main problem in the above example seems to be the foundation. Even an earthen floor should include a layer of gravel topped with a vapor barrier in my opinion. This is one place you absolutely dont want your home to "breathe". Pretty tough to do after the fact..

Iam skeptical that your climate is suitable to cob for most projects. Not enough R value for me. Would love to see any informative links you have to cob in cold climates like Canada. If you have to burn tons of manchester coal or hundreds of cords of wood to keep it comfortable, is it the most appropriate choice? Iam sure its a great choice for some projects but I would prefer to use energy more efficiently myself.
 
Rebecca Norman
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The guy wrote:
"The walls register as low as 38º towards the bottom of the wall, and the foundation about the same in the mornings. Higher up (at head height) the temperature reads in the mid 50s, and even higher it reads in the 60s. (I tested the wall temperatures with an infrared temperature sensor.)

I believe it is condensation that collects on the face of the cold urbanite foundation and the coldest bottom part of the wall (because of the big temperature difference between that part of the wall and the air inside), and then molds from not being able to dry quickly."

It must be condensation from the indoor heated moist air hitting the 38F wall. It doesn't sound from the rest of the description that it is moisture leakage or wicking from the foundation.

Earthen wall surfaces have a wonderful capacity to absorb, give back and modulate humidity (much as they do with heat). I suspect he stabilized his indoor surface with something that blocked this capacity. Certainly the urbanite (that means recycled concrete, right?) would attract condensation. Other possibilities are that his house was too airtight and the moisture level was so high that it is causing condensation. Ventilation can be a problem when we try very hard with modern materials to be highly airtight and heat-efficient. Oops, too much of a good thing!

I have direct experience of dozens of examples of this indoor humidity, non-earthen walls, and condensation effect. In Ladakh, traditional houses were adobe with earth plaster and leaky as a sieve, so there was no condensation problem. Modern houses nowadays are adobe with cement plaster, still fairly leaky, and I have seen a quarter inch of frost on the inside of windows in winter, and palpable condensation on the walls, and even on a cool summer night you can see condensation on the windows, especially in a well-closed-up kitchen. Our houses at SECMOL are made of earth, with plaster either just earth or cement stabilized, and fairly airtight but not perfect. We only get condensation on the kitchen windows at all (due to huge pots boiling), only in the cold nights of winter, and no condensation at all on all the other rooms, even with lots of dancing sweating teenagers. The kitchen also has less wall surfaces exposed with just earth plaster, and more walls covered with impermeable surfaces.

With earth building, two essential things:
Very important not to plaster with an impermeable plaster. Google "Rancho de Taos" + Plaster + damage + wall and you'll find lots about it -- this national heritage building was nearly destroyed by a well-meant cement plaster in 1967. I think lime stabilized plaster retains some of the permeable qualities and that's why lime plastered walls don't get condensation problems.

And of course, make sure you build a good foundation that lifts the start of your earthen wall above any possible moisture infiltration. But that's not the issue on the condensation problem described here.

And third, with any building, don't forget to balance heat efficiency with healthy ventilation.
 
Brian Knight
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Great points Rebecca. I think youre right about the problem being a condensation issue. High interior humidity combined with cold surfaces results in condensation.

I think its likely however, that the lack of a vapor barrier or retarder at the ground surface is one of the main contributors to the problem. There are many sources and ways to reduce wintertime humidity in homes but with such cold surfaces, I dont think any amount of breathability or lime is going to prevent condensation problems let alone comfort issues, in mixed humid and cold climates.

Balancing heating efficiency with healthy ventilation. Now that is a title of a needed new thread!
 
K Nelfson
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Brian Knight wrote:
I think its likely however, that the lack of a vapor barrier or retarder at the ground surface is one of the main contributors to the problem. There are many sources and ways to reduce wintertime humidity in homes but with such cold surfaces, I dont think any amount of breathability or lime is going to prevent condensation problems let alone comfort issues, in mixed humid and cold climates.


Moisture barriers are actually air barriers. They're used to prevent moist warm air from infiltrating the insulation, where it will condense and destroy the R value (and cause mold). I doubt a moisture barrier is needed for the foundation. The soil under and around your house must be kept dry by controlling water. If it's livable in the summer, it's probably OK to assume that the problem isn't water coming from the foundation or below. Also, at this time of year, there's no massive influx of water into the soil.

I think the problem is inadequate ventilation. Newer houses are tight enough that they need a fan running all the time to keep the moisture down. It also keeps the air moving in the right direction---cold air infiltration into the house rather than warm air infiltrating the insulation. You can also build in heat-exchanging vents to avoid pressure issues.

If it's just condensation, I'd recommend a week or possibly 2 in a hotel nearby. Run a dehumidifier in the house, install a ventilation fan. Then, turn off the dehumidifier and put a pot of water on the stove or run the shower, as a stress test.

BTW, vinegar is not the preferred anti-mold agent. Use some good old sodium hypochlorite bleach. Figure out an alternative eventually, but for now, you need the big guns.

 
Len Ovens
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Brian Knight wrote:
Iam skeptical that your climate is suitable to cob for most projects. Not enough R value for me. Would love to see any informative links you have to cob in cold climates like Canada. If you have to burn tons of manchester coal or hundreds of cords of wood to keep it comfortable, is it the most appropriate choice? Iam sure its a great choice for some projects but I would prefer to use energy more efficiently myself.


I think you are right to be skeptical about cob in "cold" Canada. There have been cob projects in Canada, including shake tests that prove they are good for earth quake zones BTW. But the only ones I know of are on the wet coast.... where I have been working outside this past week in a short sleeved shirt with at most a single layer nylon wind breaker. We might hit -3C over night once a week or so but +1C lows and highs of 5 to 8C are pretty normal. Snow that stays more than a week even 12inches deep is very rare and then because the snow insulates itself rather than cold air. Pretty much the same as the UK, wet but not that cold.

Really! we don't live in igloos all across Canada. There are some cold parts, yes (60 degrees north.... but there is a lot of Canada between 49 and 60) And yes those temperatures are C and not F, think 32 to 42F if you want. Take a look at our weather for the week. If you hit the F link in currant conditions it will convert to F. The coldest night is still 3C. I am thinking of building a cob house here, perhaps with an outer layer of more insulating cob. I am not at all sure a Wofati would handle a seismic event. At least I am not about to risk my family to try it. I notice the aboriginal peoples stopped using pit houses about 100 miles east of here even though they are related (though I don't fancy a 4inch thick cedar plank falling on me either) and wonder if that is part of the reason.
 
kim Duncan
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I recall when i was young my mum purchased a house that had major condensation issues where water would drip down the walls causing mould. The walls were painted large masonary bricks. Contractors quoted thousands. Friends drilled about 6 holes approx 10cm from the base,10mm wide. This allowed ventilation and completely fixed the issues. keep trying there will be a solution.
 
Sean Rauch
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I understand the desire to use found on site materials to build but as has been said on the forum before:

1.Yes you do want to seal your foundation as much as possible as well as insulate it from direct contact with the earth if you can. You don't want your house drawing up moisture and gasses like radon into the envelope. You also don't wand the earth to wick away heat like is happening with this home.

2. Thermal mass does not compensate for insulation, they are two different concepts with two different roles. If your in a really temperate climate where the earth never or almost never freezes and it's usually dry then yea thermal mass alone can accomplish efficiency. Otherwise you need to insulate.

3. A thermally high performance structure can inherently handle and maintain higher levels of humidity because the moisture isn't presented with a surface to condense upon. So yes always set a performance standard as your primary goal in construction everything can easily build around that. If you don't then you can have an inherently compromised structure like this one. All the energy put into an "ideal home" you can't live in and now needs major rework.

4. Take the design phase of home building extremely serious, it's not a one size fits all equation. A design that works great on one place can be a failure just a mile away. You have to ask the question "why?" a lot. Nobody knows everything, if your builder/consultant only has experience in one or two disciplines that is a sign you need second and third opinions.

5. Foundations are the most important part of your building.

6. Even if it's DIY, "Buyer beware". Don't let yourself get caught up in the hype of anything be diligent.
 
Len Ovens
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Sean Rauch wrote:
2. Thermal mass does not compensate for insulation, they are two different concepts with two different roles. If your in a really temperate climate where the earth never or almost never freezes and it's usually dry then yea thermal mass alone can accomplish efficiency. Otherwise you need to insulate.


I agree. All of the high mass designs I know of include insulation. All of the successful high mass builds I know of use insulation too. ( I have not a lot of experience in this, but I can see where the failures and successes differ)


4. Take the design phase of home building extremely serious, it's not a one size fits all equation. A design that works great on one place can be a failure just a mile away. You have to ask the question "why?" a lot. Nobody knows everything, if your builder/consultant only has experience in one or two disciplines that is a sign you need second and third opinions.


Or even two blocks away. The last house I was in before we moved often had snow on the ground when there was none just two blocks away. We were on the edge of a plateau. Where we live now is much the same. The street two blocks away has frozen water on the streets where ours thaws and dries by noon. They have more shade. Check out Vancouver Canada... Richmond is sunny, the north shore will often have rain while the sun shines elsewhere. The clouds blow up against the mountains and sit there... not a good place for a solar project.

Last thing, Don't decide that a type of building is bad because you have seen a few that have failed. There are lots of DIY things that are built by the seat of the pants with no real planning. The book on cob I have suggests owning a piece of land at least a year before choosing a site to build. This does not include the time spent checking the land for suitability before buying... I would think digging some holes before buying would be a must too. Then after all that, the house is designed to suit the build spot chosen.

So while I am interested in building a cob house and have some ideas I would like to incorporate. I do not even have sketches or layouts. One thing at a time. The land may lend itself to a different kind of building all together.
 
Sean Rauch
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Everything in context including cob. Materials and practices succeed or fail based on the context in which they are used. So this means that in some climates some materials or practices thrive while in others they fail.

I consider cob to be a thermal mass material and it will generally behave like stone, concrete or other high mass systems. This means not good for cold climates without massive energy input.

Just because you like cob and what it stands for doesn't mean it's use is either efficient or ethical in certain contexts.
 
Len Ovens
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Sean Rauch wrote:Everything in context including cob. Materials and practices succeed or fail based on the context in which they are used. So this means that in some climates some materials or practices thrive while in others they fail.

I consider cob to be a thermal mass material and it will generally behave like stone, concrete or other high mass systems. This means not good for cold climates without massive energy input.

It also would need insulation to be workable. There are ways of making a high mass home work in the cold. But traditional cob will tend to work best where it has been used traditionally. To use it in cold climates will require a rework of how cob is built. Quite honestly, I don't think anyone has done that yet. High mass does take a lot of energy, massive is correct, and so it had better be mostly free like solar collected year round and the owner needs to realize it will take a few years to charge. The number of high mass fails is high enough to make anyone take double and triple thoughts before beginning. To really analyze the ones that have been built that have worked and where they have been built and how.

One more thought on tradition building methods. People's idea of comfort has changed dramatically. We have become much softer than in traditional times. Just reading about pit houses in Delta BC Canada where children and older people stayed to keep "warm". But they did not use a fire. Warm was less than 60F. Most of us would consider that way too cold to live in. Traditionally, the whole family (minimum 8 people... think three generations) would live in one room, so body heat was a significant heat source, they would keep animals with them. Also they would have spent a significant amount of time outside. I am not only talking about the North American aboriginals either, first world people were still in many cases cooking over an open fire in the "kitchen" only 100 years ago. The chimney is only a few hundred years old too. So maybe some of the traditional builds have not been failures if the occupants had been willing to live in traditional conditions. wear warmer clothes instead of heating the building up till the walls condense water and go moldy.... move out in the summer and sleep in tents.

I would keep the RV around a few years as a backup.
 
Sean Rauch
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In "traditional times" people lived almost half as long too. I'm sure mould was ever present and it probably silently killed many children and adults before their time. I think a lot of what drove the "modern mindset" comes from the desire to live a full life.

A mass building that remains just warmer then freezing will grow mould in mass because the walls will always present a condensation surface.

Yes insulate but IMHO if you looking for ways to insulate your mass you should look at other forms of building like straw bale. There is no one solution to fix the world. Context.

 
Lucynda Riley
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I spoke with the home owner about this a few months ago. He didn't have a vapor barrier under his floor or enough gravel between the ground and his earth floor. He has since corrected this by ripping up his old floor and putting down a vapor barrier, a layer of insulation and then a thicker layer of gravel before putting down the earthen floor. He also installed a french drain around the house to keep water away from the walls. These improvements have worked.
 
Terry Ruth
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Just goes to show even the best barrier/manager out there certain clays can exceed it's moisture content index and develop mold. If the barrier used was never tested for it's interaction and chemical stability with the mix of earth there is a very good chance mold was relocated from the lower walls to the barrier. Plastic and certain insulation's like foam would be examples of a fungi food sources that cold condensation can accumulate on and provide the breeding ground for microbials since there is no mechanism for it to dry. Happens all the time. The worse part about this location is it cannot be seen so leaching will occur from ground pressures and/or air gaps in the barriers that are caused from the rigid insulation or ground moving and ripping the plastic barrier, or the barrier was installed with holes . 6-20 mil poly will not do the trick, nor will .25" according to the ASTM dart dropping test poly has to undergo to be classified as a Class 1 "vapor barrier". The design allows outward drying only and assumes the vapor pressures are always lower below the barrier which is usually the other way around in this climate zone where drying inward is also needed. If vapor pressure drive is inward any holes in the foundation will be magnified in fluid flow and leaching along with it.

In my 30 year design career I have always worked closely with Material Scientist, Chemist, to make sure that the materials I am mating to one another are compatible with the environment they are placed in and each other. Why people think that anyone can do this in this industry is beyond reason, especially when health related issues like this have risen to remind us we need the proper professionals. Hopefully they hired them before they wasted alot of time and money relocating the problem.
 
Kris Johnson
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Vedy interesting! http://www.theyearofmud.com/natural-homes-for-sale/cob-house-for-sale/ No mention of weather or not the mold issue/reason it happened was totally eradicated or not.

This http://www.theyearofmud.com/2012/02/29/lime-plaster-and-wash-on-cob-or-straw-bale-wall/ was the last post I found on the subject and it seems his solution was to lime wash the bottom half of the wall. But I didn't find any update as to weather or not that solved the issue, which sucks and would be super helpful. I inquired to Ziggy about the matter, hopefully he replies.
 
Kris Johnson
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Here are a few posts of the foundation build.http://www.theyearofmud.com/2008/05/06/first-course-of-foundation-complete/ http://www.theyearofmud.com/2008/05/15/urbanite-foundation-mostly-complete/ http://www.theyearofmud.com/2008/05/20/cobbing-begins/ They seem to give some insight to what caused the eventual mold problem but I am not really sure. Perhaps the urbanite combined with the filling in of the cracks with sand and clay allowed water to wick up into the cob walls and cause eventual mold problems. I thinks its safe to say that some sort of capillary break in the foundation wall would have stopped water from infiltrating into the cob.

Sadly it looks like he has, instead of learning from his mistakes, completely turned his back on cob and instead moved onto starwbale. Not that strawbale is bad or less than appropriate in his region, but completely dismissing it without understanding the reasons the mold occurred seem like an even bigger failure than the mold issue itself, for everybody.

And to never consult someone professionally that has experience with cob, but to ask his readers for advice?!? And then simply cover up the mistake and hope that solves the issue! And on top of it all to try and sell the thing to somebody!!! That's just irresponsible.

What happens when a home typically gets infested with mold? Everything gets ripped out and replaced, sometimes with or without the cause of mold being solved first.

The best thing he could have done was to tear down his gobcobtron, learn from his mistake and start over.

Sorry for the rant.
 
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