Tag Archives: Earth Shelter

Burial Phase 2

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Posted on October 1, 2017 by

 

In the previous two segments, we put dirt over the shotcrete and then added our waterproof insulating umbrella.  In this segment, we put an additional layer of dirt over our umbrella, then plant grass and work on the retaining walls.

For your viewing pleasure, here is the timelapse video…

Video

Lessons learned

  1. As always, not everything makes it into the videos.  One part that didn’t quite make it was adding the layer of blocks along the top edge of the wall above the back door.  That wall is an ICF wall, basically 6 inches of reinforced concrete poured between two sides of insulation.  We put a good amount of blue max waterproofing on the top edge and then I made sure that the billboard vinyls (17 mill reinforced)  also overlapped the edge and I mortared 3 layers (about 12 inches) of block along the top edge to hold it all in place…  I thought this would be good enough.  However, water finds a way…  It was able to get between the ICFs and the concrete and run down the inside of my wall all winter…  I’ll need to tear those blocks off and put in some continuous metal flashing at some point.
  2. When we started laying it out, I assumed that the experts would know what to do.  Of course, they were pretty uncomfortable with my not having a detailed plan, but were nice enough to work with me. So, the first lesson learned was that I really should have come with a plan and not put that on the contractor.  As it turned out, I really didn’t bring enough blocks to for that back wall.  Some sort of math problem. So that was my second mistake.  The compromise solution was to turn the blocks side ways and lean them back against the hill…  I know this is not ideal and I already expect a lot of negative comments on Youtube.  I decided the only way to overcome that was to put a lot of concrete and rebar behind the blocks to tie them together and form a continuous dam.  This chewed up a bunch of time, but it is over a year (two winters and two springs) later and the wall is so solid that the mortar hasn’t even cracked.

 

Other tricks up my sleeve

Sherri was concerned that someone would fall off that boulder wall, in fact, she always calls it the “death wall”.  She insisted that I put a rail along the top and bottom edge.  I wanted that rail to be as slender as possible and decided I could use copper pipe for posts and rails.  This isn’t against code if I don’t put a walking path within 6 ft of the rail.  When used as the posts, the copper pipe would be much easier than a wooden post to attach to the boulders…  Just drill it in.  The problem is that it wasn’t really stiff enough.  I found that “L type” copper pipe was quite a bit thicker and stronger, but I still wouldn’t want to rely on it.  I also found that 1/2 inch L copper fits almost perfectly inside 3/4 inch L copper…  This made it more than twice as stiff, especially if I filled the gap with epoxy…  So that is what I did.  The last problem was that the holes were not drilled perfectly vertical (that is harder to do than you might think), so you see they are a bit off plumb at the start, but later we were able to bend them vertical.

The Gallery

Here are some pics, mostly just old scenes since this wasn’t really a photogenic stage.  Enjoy.

 

Burial, Phase 1.

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Posted on September 9, 2017 by

Our earth-sheltered house design uses an “umbrella” concept to retain the heat and keep things dry.  This post covers the first phase, the dirt under the umbrella.  Still, it was a big step.

The Video

The Gallery

Often the story is best told with pictures anyway…

We don’t like our underground house!!!

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Posted on May 11, 2013 by

Well, hopefully Sherri and I will love our underground house.   “We don’t like our underground house” was the title of a blog by MizBejabbers who wrote about the pitfalls of her underground house.

MizBejabbers earth shelter in Arkansas.  Check out her site for more pics, but there aren't any good ones ;^)

MizBejabbers’ earth shelter in Arkansas. Check out her site for more pics, but this was the best one ;^(

 

Miz tells about how they moved into an earth sheltered home 18 years ago (built by TerraDome for a previous owner, who may have covered up the problems to sell it) and how it has not lived up to the earth sheltered promise.  She writes about how it had all the fears (leaks, mold, etc.), but without the benefits of energy efficiency.  She also talks about increased construction cost, severe depreciation, pests (bugs, rats and nosy people), etc.  She does have a section on “happy things” such as feeling safe during storms, enjoying the peaceful quiet, etc. but concludes that these were not worth the pain.

She even blogs about mini tremors, which she thinks are earthquakes cracking the house, but I suspect it is the house cracking and settling as the soil underneath is slowly eroded.  No earthquakes required.

 

For someone like me who is considering a similar investment, this could be a blog from my future, so I read it very carefully…

My conclusion was that this house was just designed and built really badly and in the wrong time and place.  By time, I mean that it was built in the early 1980’s when few people had worked out how to do these properly.  Lets go thru the issues, as far as I can tell from the blog.

The site:  This house is set below the road on the side of a large hill overlooking the Arkansas river.  The U-shaped design that Miz mentions sounds perfectly designed to catch all the surface runoff from the hill above and funnel it toward the front door.   What is probably happening under the ground is even more threatening…  Hills do interesting things to water tables and an earth sheltered home may be sitting in an underground aquifer, like a wet pebble in a stream.  Try a quick Google image search for “artesian well diagram” if you are not familiar with the concept.  Miz acknowledges that the french drains are not sufficient in capacity or well placed to drain water away before it enters the house.

Our site doesn’t have such a majestic view, but it is on the top of a hill, and our hill is very permeable sandy loam that will dry out nicely.  Before I bought my land, I walked around during a thunderstorm and made sure the water didn’t collect or run.  After buying the land, and looked “deeper” and buried moisture sensors more than 10ft down for my Soil Temperature Experiment.

The construction:In the comments after the article, she mentions that the house was built on fill (to make a terrace on the side of the hill).  If there was water flowing down, around and under her home, fill soil would wash away more easily and would lead to further settling and cracking and leaking.  My home will be built on undisturbed soil with a high compression rating and no erosion threat.

She also blames a “bad batch of concrete” for the living room roof crumbling.  I am not sure if that was really the problem (or if the bad conditions just wore down otherwise adequate concrete), but The TerraDome homes are monolithic structures which are poured into proprietary modular forms.  If the concrete is not carefully mixed and poured, there is no good way to fix it later.

My home will use shotcrete, which (when done right) is considerably stronger than any poured concrete because of its lower water content and the way it is compressed as it is shot onto the wall.

Miz mentions metal ducts rusting and falling apart, I will be using only HDPE ducts that will never rot or leak.  We also plan to heat our home with radiant floor heating, a method better suited to the heavy concrete construction.  We will still have ducts, but only for ventilation and de-humidification.

She mentions drywall rotting and molding, internal wooden walls being eaten by termites, etc. we won’t have any of that in our all concrete house with a specfinish gunnite surfaces.

The waterproofing: TerraDome, like other earth sheltered builders (including Formworks) with “proprietary systems” does not use a waterproofing umbrella.  Instead they insist on more traditional methods used for waterproofing regular basements, glued or sprayed directly to the walls.  These include bentonite clay or a “tar modified polyurethane elastomer applied as a liquid”.  These directly applied methods are pretty useless if the concrete cracks more than 1/16th of an inch.   Even applying something like a pond liner right over the concrete before backfill is not as good as an umbrella (away from the concrete) because it can be torn by the movement of the concrete and does not help with thermal mass.

Applying the waterproofing and insulation directly to the structure also excludes the surrounding thermal mass and allows water percolating thru the ground to strip it of its heat, both of which reduce thermal performance when compared with an insulating umbrella.

It also sounds like the soil around this home was not properly drained.  The French drains mentioned are not well placed or of sufficient capacity to handle the location on the side of the hill.  This moisture increases the weight and lateral (hydro-static) force on the walls.  Cycling moisture levels are even more damaging.

An interesting side effect of applying the waterproofing directly to the structure, and then draining around it, is that you need to make a choice about the moisture level of the soil above the water proofing… Do you want it to be dry for the structure beneath or do you want to keep plants living on the surface?  It is difficult to have both.   Miz ended up shutting down her sprinkler and letting her plants die.  Eventually, they had to remove the covering soil completely.  The umbrella solves the problem by requiring that you drain only the soil under the umbrella and allowing you to maintain the moisture in the soil above.

 

My home will use an umbrella with three layers and I plan to go overboard on the french drains under the umbrella.  It also helps that my soil is very permeable.

Conclusion:  I think I can avoid the problems shown in this blog, but I need to keep my eyes open and be as careful as I can.  I am sure the builder of this home didn’t expect these problems…  And neither did poor MizBejabbers when she and her husband bought it.

Caveat Emptor!  Buyer beware!  When buying an earth sheltered home, you must be doubly careful to check it out before buying.

What is the latin phrase for “this may be harder to sell?”  There is always some mistrust between the seller and the buyer, but this gets worse when the item, your earth sheltered home, is difficult to inspect,  because it is buried, or difficult to compare, because it is unique or custom built.  Economic Game Theory would suggest that because the seller knows much more about the house than the buyer (informational asymetry), he would only be willing to sell the home at a deflated price if the actually thought it was worse than the buyer thought.   Sellers who’s homes have no issues would be less likely to sell for less than they thought the home was worth.   This would reduce the percentage of good earth sheltered homes on the market even further.   Buyers could deduce this and realize that a large portion of earth sheltered homes on the 2nd hand market are likely being dumped by their owners.  Therefore, sellers would be willing to offer even less.  This is why earth sheltered homes tend to suffer heavier depreciation than other homes even thought they should last longer.  Blog articles and anecdotes and even random experiences with cold damp basements only make it worse.

If you want to prevent or at least reduce the depreciation of your earth sheltered home, just in case you ever need to sell, you can do things to reduce the buyer’s doubt.   I will start by taking detailed photos of the construction.   I also plan to bury sensors (temperature and moisture) and keep good long term records.  Other maintenance and utility records also help to establish the efficiency of the home.   Not painting, or other wise covering, the inner surface of the home will also help to preserve trust during the sale process.   The effect of these efforts would be similar to the effect of selling a used car and including a full set of records; including gas mileage for every fill-up,  maintenance records, a car-fax report, etc.  Increased buyer cconfidence will translate into higher offers.   Of course, it only works if you actually build a good earth sheltered home ;^)

 

The blog mentions their attempts to enforce a warranty or get money from TerraDome or the builder, or the previous owner, but all failed.   I don’t expect to get a warranty and I will have no one to sue but myself, so I will need to select the builders carefully and make as sure as I can that the concrete mix is a strong one.