DIY Hobbit Hole Part 2

21st Century Bag End

The Dragon, who is genetically predisposed to underground dwelling, has previously posted a DIY Hobbit Hole. This link is not so much a finished project, as it is a theoretical approach. It is informative nonetheless, and I hope someone else out there is inspired to give it a whirl, or incorporate some of it's ideas into their own geeky-green plans. I'm definitely stashing it away in the old mental file.

The largest expenses in building a home (not counting the flat screen tv and indoor lap pool) typically are the walls, exterior and roofing system. Obviously, the roof and exterior are done away with for Hobbit Holes. However you have some staggering stress and loading issues with underground housing. The weight of the soil and flora growing on it can produce tremendous loads on a structure. It is even worse when it rains.
Once you start doing the math for wooden structures, the cost quickly skyrockets. On top of high costs to support such loading, you have yet to deal with the issue of water seepage, insect vulnerabilities (termites) and wood rot.
That leaves us the two building materials. Steel and concrete. With the circular nature of Hobbit Holes, one could use large steel pipe, but no source exists that makes low cost steel structures that I could find. But concrete... yes... concrete is the ticket.
All around the world, companies manufacture pre-formed concrete pipe... LARGE concrete pipe. Concrete pipe has several advantages for making Hobbit Holes. They come with an assortment of flanges, protrusions and options that allows for the creation of windows, skylights, doors, garages, fireplaces and chimneys.
As one can see, using such materials for the construction of a Hobbit Hole would make for a comfy home. Or at least a conversation piece.
Although the elliptical may have some aesthetic advantages, the use of round concrete pipe may be the best choice. The main reason is that you will need to have room to place plumbing, ventilation, electrical and communication hardware though out the Hole.
The best solution for this is the area under your flooring. The best example of this type of construction is in naval architecture with sailboats. Plan all of your plumbing, ventilation and wiring, then figure out how much space you will need, vertically. Maybe the use of multiple styles, circular for halls and elliptical for rooms, is the best idea. The halls would need the most space for plumbing, etc as all rooms connect to it. That is the design philosophy I have used for Bag End 2.

Check out the floorplan graphic here.