Earth Sheltered Timeline, 2013
January: Finalized the design of the Storm Room, which meant we finally had a good idea of what the house would look like. I also worked out some details of the mechanical room, etc. with 3D models.
February: I shared the architectural plans with the building inspector who then contacted the architect directly to discuss some minor changes that would make things easier to approve. Got a set of engineering drawings and had a lot of concerns, set up a meeting for March 1. Finally settled on a set of windows, also got quotes on things ranging from ICFs to a glass floor between the storm room and the rotunda below (it was too much). Sherri met with some kitchen places to get some quotes. I had a google hangout with the architect to discuss water drainage and other issues.
March: Met with architect and engineer to try and get things back on the right path and fix some aspects of the design, especially simplifying the structure at the front of the house and fixing some thermal issues. At the meeting, I mentioned the high cost of the glass floor and the architect suggested a steel grate instead… At this point the hours of work remaining seem few, but the weeks stretch on… I also met with the Shotcrete contractor to make sure things still looked build-able to him, he seemed very comfortable with the whole idea and that made me a little nervous, but not as nervous as if he looked nervous ;^). I also got quotes on the large precast ribs from several precast companies.
April: Perhaps as an April Fools day joke, the architect/engineer sent a bill stating they were 100% done… and the Engineer was asking for more money beyond the agreed amount for “scope creep”. Instead of paying, I wrote out an itemized list of the issues along with dates of emails sent on each topic. Basically, I established that the things I had asked for were in the very first emails and the later emails were just trying to get them to pay attention to the original emails. Instead of forwarding the letter to the engineer, the architect decided to continue working on everything else so he would only need to go back to the engineer once at the end. In April, I was sent the “penultimate update” of the drawings, but I still found many issues (many I had already mentioned, but some were new). The neighborhood where I am building also had a “work day” to trim and remove trees that were too close to the road. I went out to help out
I will come back and fill in the missing months when I get a chance…
=> Things really get going in 2014
Progress seems to have stalled, or at least we are not aware of any in the past week or so. I thought we were moving at the start of the month, but I have not heard much lately. I emailed the architect again today to ask, but with the long weekend coming up…
In the mean time, I have started purchasing components for my temperature sensor array. This will help me monitor temperatures under the home, as well as some of the earth tube and internal temperatures. This project will require me wiring up the semiconductor chips to some circuit boards, writing code, etc. I bought, and already mostly read, an ExtremeTech book on the subject. I also purchased some circuit boards and a USB connection from www.hobby-boards.com.
DS18S20 from Maxim Dallas Semiconductor… I will build an array with these, wire them into a circuit board, connect that to my computer and write code to record and display the temperatures under and around my home…
I separately ordered some DS18S20 one wire temperature sensors directly from the manufacturer, Maxim -Dallas Semiconductor, because Hobby-Boards wouldn’t meet their price. Maxim is actually being somewhat strange about it and require that I send in a signed statement saying that I don’t plan to use them in military applications or resell them… I need to get this all figured out ahead of time so I can test/debug the array before it gets buried. The soil temperature experiment used more expensive plug and play sensors, but these ones cost just a few percent of the price, allowing me to afford many more of them.
We have also got going on the bank paperwork. Part of the construction loan process is something called the “Sworn Statement”. It is a big long document where I will list the names and estimates from all my contractors, etc. The second page asks for information about the type of construction, down to detail such as the type and spacing of the floor joists or if the gutters will be aluminum or vinyl. It even asks about “sizes, features, brand, etc.” for the microwave. This is quite a paperwork hurdle, but I can understand why the bank would want to be sure we have our ducks in a row. Trying to put a positive spin on it, I guess this paperwork gives us a framework to organize our quotes over the next 6 weeks or so.
No time for eye candy today…
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 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.
