Working with Builders, Architects and Engineers in Tennessee

Hello

My partner and I are considering a piece  of land in middle Tennessee. We spoke to a builder there about building an Oehler style house and he informed us that county regulations would require that an underground house must be entirely concrete and would require drawings stamped by a structural engineer and civil engineer to be permitted. He also said he was unable to find any engineer in the state that wanted to touch the project.

Is there anyone out there who’s built one of these in middle Tennessee? If so did you use an engineer and would you be willing to share their info?

Is an underground house even a good idea in that climate? (Hot, humid and wet. Maybe termites)

Do we have to work with the “concrete terrorists”?

Any help would be greatly appreciated

I am a Civil Engineer in Australia.

There is a big difference between and 'underground house ' and a 'Oehler style house', and few would be aware of that.
Its my guess the builder is thinking of a concrete shell covered in 3-4 feet of soil.

Does your builder know the difference?
Perhaps do some sketches, you dont need an architect for the drawings. In fact I would avoid and Architect, because unless you find one that knows about these homes, he will be lost.

Search for builders who have experience in these structures.

Thanks for responding

our builder has never done anything like an Oehler-style house before. he said he's done eco-builds that were all concrete. we were kinda handed him by our realtor but he's been doing his best to help us out.

I sent him a few renderings with the basic idea (same as below)

do you know of any good places to search for experienced builders?

Rendering

I am in Australia.
You will need to do a bit of research across the internet.
Research is easy for me, I was trained to do it.
If you have limited experience start on Permies with a request for Builder recommendations for what you want.
I would include building with logs, partially underground etc.

IE "Seeking recommendations for an experienced  Oehler-style house builder."

Then I would look for people who talk about these structures, try Forums and read what is being said.
Join up and ask questions.

Jacob Sohni wrote:Hello

My partner and I are considering a piece  of land in middle Tennessee. We spoke to a builder there about building an Oehler style house

I hope you will get the replies you are looking for from Tennessee.

I would like to ask what your county requires?  Do you need a permit to build on your property?

These types of structures are not built every day so finding a builder with this kind of experience or even the equipment needed to build one is probably rare.  I hope you will find someone.

im not sure about middle Tennessee but here in east tn I know that even my underground root cellar gets lots of moisture that underground gets so much mold its useless for anything that isn't canned or bottled. I guess its the high clay content and chert soil that just doesn't dry out and allow underground drainage. it might not be ideal for underground living.
but fungi and mushrooms grow real well here.

Yes, check with the county with your own eyes and ears.  A company I do some work for insisted a plumbing project was going to cost us $60,0000 because that is what the plumber told them was needed to meet code.  In checking with our city, it turned out to be $10,000.    No, the plumber was not a crook. He had just done work in a community 60 miles away and assumed the permits and code would be the same.

Which county?

Although they don't talk about it, many counties have a "weekend" cabin clause.  Under a certain size and off grid doesn't need a permit.  

As for ohler style, that is kind of risky in Tennessee.  Wood rots WAY faster in Tenn than northern Idaho.  I'm not saying it won't work, but you need to be really careful and weigh the risks.  

Potential site is in Montgomery County and we we’re shooting for under 1200sqft. Don’t know about being completely off grid just yet. We are trying to see if it could be classified as a fallout shelter.

I’m worried about the moisture as well. The key will be keeping moisture away from the wood. My other big concern is termites. Are they bad in Tennessee?

If you have termites, forget about wood in the ground.
Could you bring yourself to use secondhand steel posts, pipes etc?

https://imgur.com/a/EW9ltD7

Here is my stab at an Oehler-inspired foundation for a wet climate like Tennessee.

The drawing is basically a mix of pier-and-beam foundation with an Oehler structure. The main thing I was trying to achieve was not letting any wood directly touch earth or concrete.
I set the main supporting round wood timbers on a concrete pier separated from physically touching the concrete by a rubber gasket, hopefully preventing any wicking of moisture from the pier. The timber is held in place with a rebar pin. I understand that the lateral forces from the earth can cause hinging at the point where timber meets pier. So my thought was to use a steel bar to brace the bottom, hopefully preventing any hinging.

The foundation slab itself will be pitched in order to allow any water that did enter the building to be directed to a low point and pumped out. The slab would be wrapped in rigid foam to provide insulation and set on crushed rock to allow any ground water to drain way from the foundation.

We didn’t want an earthen floor and we also didn’t want a concrete floor so I decided to use piers with timber hangers to create a wooden floor with essentially a crawl space beneath. Since the floor joists are separated from the concrete piers by the metal hangers we shouldn’t have any wicking issues here. My one concern about this setup is condensation forming on the bottom side of the floor from temperature differences between the crawl space and main living area. Does anyone see a problem with this?

The walls of the structure are pretty much straight from Oehler’s book. PSP style. Support posts, wooden plank shoring wrapped in a waterproof pond liner. A layer of sand will be added to protect the pond liner from puncture then another layer of rigid insulating foam. Finally a French drain to funnel water away from the walls of the home. Then bury the whole thing in dirt.

Anyway just thought I’d put this out there to see what people thought. I’d love any thoughts or criticisms.

Thanks

termites are bad here, the kind the come from underground and build vertical mud tunnels . I have lots of red cedar and I dont think they like it but they build those darn mud tunnels everywhere to get to something they like to eat.

the longer I live here the more I realize there is a reason why so many of the wood residential buildings, sheds and outbuildings are built on piles of rocks way off the ground.
the heavy clay soil does not to let go of moisture in it. even some very very old log cabins ive seen are built on top of piles of rocks at the corners.

bruce Fine wrote:the longer I live here the more I realize there is a reason why so many of the wood residential buildings, sheds and outbuildings are built on piles of rocks way off the ground.
the heavy clay soil does not to let go of moisture in it. even some very very old log cabins ive seen are built on top of piles of rocks at the corners.

Sometimes, it's easy to think that we modern folks have superior knowledge at our fingertips and that the old-timers were working without all the advantages we have. We can be blinded to the obvious logic that is right under our noses.  

Jacob, I dont think condensation will be an issue.
Its caused in part by temperature differences and since the concrete and the wooden floor are close, the temperatures will be close.

FROM; cause of condensation

Condensation occurs when warm air collides with cold surfaces, or when there's too much humidity in your home.
When this moisture-packed warm air comes into contact with a chilly surface, it cools down quickly and releases the water, which turns into liquid droplets on the cold surface.

I recommend these guys.
https://www.structure1.com/services/precision-structural-engineering/

In the underground book the roof is made to handle 2ft of dirt.
Its possible that you want to limit it to say 3-4inches of dirt (18lbs per sqft) and then your structural requirement wood be less.

I recommend building the tiniest simplest one bedroom house, legally with 400Amp electric service.

And then build an underground 28ft by 36ft "farm building" with cash. Usually you dont need an inspection or maybe even a permit.  Maybe we can call it an experimental greenhouse or something. Then once the shell and roof is built, just run your own electricity and plumbing.  

Are you building with a post/grider/beam every 6ft. What does your house plan look like?


Attached is an image of what the inspectors will rubber stamp. Its called Permanent Wood Foundation .  

Jacob Sohni wrote: My other big concern is termites. Are they bad in Tennessee?

Here in East Tennessee, both termites and carpenter ants are of concern. Been looking into the most energy efficient small house design to build for a good many years now. The 4-foot thick thermal mass walls of Michael Reynold's earthship designs seem to be the way to go. However, instead of auto tires for the walls, I'd build with CMUs', back-fill with earth to get the 4-foot thick walls, plus the insulation and vapor barrier between that and the additional berm-fill. Such construction would be termite proof, carpenter ant proof, and fire proof. Ventilation (earthship style 40-foot long 10" diameter cooling tubes buried in 8-feet deep earth, sloping away from the living space) are supposed to keep fresh, temperature and humidity controlled, air flowing through the living space. Still looking for data on just how effective the humidity reduction works with those "cooling tubes". Any earthship dwellers feel free to chime in.

The CMU's will need support to hold back dirt, depending on how high you build them.
2 feet high is too high without either reinforcing bars extending up from concrete foundations, or galvanised straps laid in the soil and attached to the blocks with through bolts.
Many modern road cuttings use them.
Its called reinfored earth embankments, where something like seltbelts are set out and covered, with one end attached to the face oif the embankment.
In your case to the CMU.

I looked extensively into earthships and other types of semi-underground housing for a project I am planning in Louisiana.  I ran across this article: https://theministryofarchitecture.com/earthships/tips-tricks-to-make-earthships-work/  about the pros and cons of earthships in different climates and it was pretty emphatically against the idea of any kind of underground housing in a high-humidity climate.  

I also thought about historically how the pioneers in the area handled the climate -- houses off the ground, sleeping porches, houses with cross sections open to the breezes -- and I concluded that a lot of the natural building styles which are popular in permaculture are not that suited for hot, humid southern climates.   Looking to the tropics for inspiration, especially since the climate in the area will be changing towards more tropical, is probably a better path forward for natural building suitable for this area.

I also think it might be a good idea to build a series of smaller, different types of structures for different purposes and/or different seasons of the year.  For example, an off-grid bamboo hut enclosed by mosquito curtains and elevated off the ground might make for a lovely cottage in the spring or fall.   Perhaps a partially underground shelter, or a soapcrete dome, might be a good winter building, and/or hurricane/tornado shelter.  For the hottest days of summer, an on-grid tiny house with air conditioning might be the best thing especially for those susceptible to the heat!  :)

I am living in East Tennessee, but years ago I lived near Fayetteville Tn (middle TN). In most counties outside of big cities here in Tennessee you DO NOT need a building permit or inspection for the structure. You only need the septic inspection and the electrical inspection for the building. I would be looking for a county that is rural and doesn't have the gestapo inspectors.

That being said, I am a Carpenter and I build houses all over East Tennessee, North Georgia, and North Carolina (sometimes). I build mostly for prepper/homesteader types and in the counties that I build most of the time there isn't any inspection, or permit. The smaller towns are different if you are inside the city limits, but for instance: I just built a 1400 square foot house inside a small town, there was no inspection on the framing but they wanted you to pay for a permit!