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Okay, lets design a Hobbit Hole

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Joined: 30 Jun 2007
Posts: 16
Location: Oregon

PostPosted: Wed Jan 23, 2008 3:45 pm    Post subject: Okay, lets design a Hobbit Hole Reply with quote

I think Log Rhythms, Inc., my design company is going to go ahead and design a hobbit home...with or without permission from the Tolkein Lawyers. Of course we can't call it "Hobbit" because that is an infringement on copyright. So from here on out it will be called "earth sheltered", people sized, built to code, practical, and not in-expensive. Our goal will be to take a flat piece of ground and build or at least design (including virtual walk-thrus) of a comfortable earthsheltered home. No short-cuts, goofy glass bottled walls, un-likley energy sources....none of that. Something that is totally cool...and works! And works for a long time. for me that means access to utilities, ease of maintanence, appreciation, quality building materials, and quality art and craftsmanship.

Okay, the gauntlet it thrown.... I will keep you posted of developements. If you have any thoughts about basic design, materials, considerations, pitfalls.....let me know.
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Joined: 25 Jun 2007
Posts: 40

PostPosted: Fri Jan 25, 2008 9:06 pm    Post subject: Large concrete pipes? Reply with quote

I think the easiest way to get a quick and dirty hobbit hole would be to bury large inter-connected pieces of concrete pipes. I mean using huge water-drainage pipes that are 15 feet or more in diameter in various shapes, then sealing them together with pitch to make them water-tight and burying them underground. Then once the outer shell is completed, building a more cozy wooden interior. I'd probably want to build bookshelves and storage into the curved walls on the side, and a curved wooden ceiling to preserve the rounded shape.

Building a raised wooden floor with trapdoor access would allow you to run all your interior plumbing and wiring in the bottom curved portion of the pipe afterwards with easy access while creating a flat floor. You could probably even heat the air in the enclosed conduit so the floor would be warm and put in vents so the heat could rise up to warm the living quarters above.

I guess the main question would be how difficult it would be to cut the concrete piping, and figuring out how well structural integrity would be maintained depending on how many cuts you make for windows, doors, and skylights. I'd want a full lawn on top of the dirt covering the pipe to prevent erosion, but you'd probably have to be careful to keep trees or anything with strong root systems from developing, or they might crack the cement eventually.

Anyone else have ideas for a simple main structure?
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Joined: 22 Mar 2008
Posts: 1

PostPosted: Sat Mar 22, 2008 11:48 am    Post subject: Reply with quote

You really don't want to cut the concrete pipe. You want to order the concrete pipe with whatever tees, flanges, and connections you need already integrated during manufacture. All joints should be lap joints, not butt joints.
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Joined: 26 Apr 2008
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Location: eastern shore of Virginia

PostPosted: Sat Apr 26, 2008 8:11 pm    Post subject: Large Pipe Reply with quote

Having installed many pieces of the larger sizes of pre-cast concrete pipe I can assure you that IT IS NOT THE WAY TO GO. First off, the larger sizes of pipe - cylindrical - over 8 ft. in diameter - and the larger sizes of elliptical - say over 10 feet (long dimension) are not cheap. Second - and probably more important - this stuff is very, very heavy. A piece of elliptical pipe large enough for a room weighs several thousand pounds per lineal foot - and they come in standard 8 ft. lengths. Without cutting a standard piece of pipe, or order a custom length, the rooms with be 8, 16 or 24 feet long x the width of the pipe. For the full-size sections, you would need to rent a very large capacity crane (100 tons or greater) to place these pipes. The trucks that transport them would need to be able to drive right up next to where they need to be placed as extra handling is time consuming and expensive.

The ground under the pipe would need to be able to support far more than the weight of a conventional house. We are talking about several hundred pounds per square foot empty. In heavy construction, we often need to place 2 to 4 feet of stone under the pipe - and it still ends up settling a little. For a dwelling, where the floors stayed level and did not move out of alignment, it would be required to place a reinforced concrete footing under the pipe - an additional cost.

This large pipe has very thick walls - at least 10 inches, and some of the largest elliptical pipe has a wall thickness of over a foot. It is designed to be buried just a few feet under a road carrying a few score tons. It can also be buried 20 feet below grade and then backfilled and compacted. It is way over designed for the purpose of using it for a dwelling buried with 2 to 5 feet of dirt with grass on top.

While the concept is very good, the actual use would cost hundreds of dollars per square foot of living space before any of the interior was finished. I toyed with this method myself a few years back, and found it to be just too expensive for materials and labor and equipment.

I have wanted to build a "bag-end" style house for some time, and I have spent the last few years researching the various building methods that could work. I have come to the conclusion, that the cheapest (in material cost) and the most reasonable in terms of labor, is to build with ferrocement using high strength wire mesh and high strength mortar.

For this type of construction, on hi-tensile steel welded wire mesh and #4 (half inch) rebar is used - with expanded metal lathe on the inside for a better finish. Chicken wire must never - ever be used for ferrocement construction for any dwelling that will be backfilled - it just isn't strong enough. The mortar strength should be at least 8,000 psi. With several layers of mesh (4 x 4 - 9 GA) plus #4 rebar 12 inches on center each way - with a finished thickness of 2.75 to 3 inches, you would have enough strength to support at least 5 feet of lightly compacted soil over the structure.

One great advantage of ferrocement construction is that the individual components are relatively easy to handle. The individual rebar pieces can be handled by one person, or better a couple - and the wire mesh, which is supplied in 5 x 10 ft sheets can be trimmed and placed over the rebar after the basic shape of the structure has been determined.

Also, with ferrocement - you will be able to replicate the basic design of Bag end including the high (in hobbit scale) vaulted arches in some rooms and the rounded sections of the connecting halls.

If the area is available, it would also be better for general living - and may be required by code - to have all of the rooms along the same line - straight or curved - so they all have at least one window. Imagine that after entering bag end - instead of only being able to turn left and having rooms on each side of the back hallway, they was another hallway and row of rooms on the right of the entry. Only a few closets, pantries and storage rooms need be on "the backside" of the dwelling with no windows. The "back hall" could extend each way with an additional entry/exit door at each end. Thus, when looking at the "hill. there would be a main entrance at 6 o'clock, with an additional door at 2 or 3 and one at 9 or 10 - depending on the curve of the hill, etc.

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