Ultra Low Cost Housing

Ultra Low-Cost Housing

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M.Subhash Chandra L.Aditya

GITAM UNIVERSITY


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ABSTRACT The greatest material need in the world today is the need for housing and life-

support systems for the sustainable development of civilization. In western countries

such as the U.S.A., housing is no longer affordable by a large percentage of

Americans. In developing countries, housing is both substandard and expensive.

Therefore, affordable housing and the ability to sustain civilization without destroying

the environment are the critical needs in every country of the world today. Unless we

solve the world housing shortage and provide a means for people to sustain

themselves in life supporting environments, the world may erupt into competing

battles for resources.

So, definitely there is a need for development of low cost, high strength, low

weight and environment friendly houses. This is possible only by using natural and

agricultural products in the field of construction. We use new engineering principles

and new types of building laws and techniques in design of these low cost and

environment friendly houses. There are several aspects which influence this design.

This design and construction process is completely explained in this paper.


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INTRODUCTION The greatest material need in the world today is the need for housing and life-

support systems for the sustainable development of civilization. In western countries such

as the U.S.A., housing is no longer affordable by a large percentage of Americans. In

developing countries, housing is both substandard and expensive. Therefore, affordable

housing and the ability to sustain civilization without destroying the environment are the

critical needs in every country of the world today. Unless we solve the world housing

shortage and provide a means for people to sustain themselves in life supporting

environments, the world may erupt into competing battles for resources.

ENGINEERING PRINCIPLES Bending moment

`The single most important principle for the strong design of structures is called

the bending moment. Basically, a moment in engineering parlance is the principle of the

lever. If you want to tighten a bolt, you can hold a wrench close to the bolt or you could

grab the wrench at the end. The end of the wrench gives you more advantage. The

distance at which a force acts influences the outcome. That is the principle of the

moment.

Likewise, the strength of a structure is not just a function of the kind of material it

is made of, but how it is shaped -- the distances involved. Take three 1/8 inch thick

boards 2 ft long and 3 inches wide. If you were to place them flat on top of each other

and support them on the ends only, you could easily snap them by stepping on them with

one foot. However, if you were to construct a triangular beam out of them, they would

probably support your whole weight.


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So the moment is the combination of force and distance -- the force times the

distance from the axis that the force is applied or resisted. The bridge truss, the box beam,

and the I beam all take advantage of this by putting the strongest material at the outside

edges -- as far as possible from the central axis. The material at the center takes no force

at all. The material at the edges takes all the force and maximizes the strength.

Remember the principle of the moment: It does not matter much what the inside is

made of, if the outside edges are strong, the structure will be strong. You can make a

house out of material as light and fragile as styrofoam and it would be strong enough to

fly if the surfaces are coated with a strong material. Use this principle in the design of all

your structures!

Curved Surfaces -- The Shell

Curved surfaces, shells, are stronger than flat surfaces. Take three sheets of

material. If one sheet were curved along one axis to make a half cylinder, like a quonset

hut, the strength would be several times that of a flat roof. A heavy snow load could be

resisted. If a sheet were curved along both axes to make a dome, the strength would be

greater still. Surfaces curved in two dimensions can be 40 times stronger than flat

surfaces! This is the strength of the curved shell. Use this principle of shells to increase

the strength of your structures! Actually, the curves only increase the distance of the

material from the central axis, taking advantage of the principle of the moment just

discussed. An egg shell is a great example of significant strength from a tiny amount of

material.


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Corrugation

You've seen corrugated sheet metal. The corrugations give it greater strength in

the direction along the corrugations. Again the principle of curved surfaces and the

moment are put to good use. Corrugations can be deeper than the usual corrugated metal

sheet roofing. The deeper the corrugations the greater the strength, because the moment is

greater. Serpentine walls take advantage of this corrugation factor. Curved walls only one

brick thick have stood for centuries. Many fan-type sea shells use corrugation as a

strengthening principle.

Honeycombs

If you've ever seen a paper wasp nest or a bee hive, you've seen a honeycomb.

Honeycombs are used to maximize the use of materials. A honeycomb with a shell on

each side is one of the strongest structural engineering designs. We use this idea for dome

shells, walls, and virtually every other construction.

Stress Points

The reason most structures fail is not just because of the weakness of the material,

but because of its connections to other materials. Connections such as bolts, nails, and

screws cause localized stress points near the connections which fail long before the

material itself would fail. It is these localized stress points that are the weakest link in

conventional structures. It would be better to avoid localized stresses altogether if

possible. This can be done by not using localized stressors such as nails, bolts, and

screws. Instead, connections should be continuous, like ribbons. Ribbon connections

continuously tie two surfaces together and prevent localization of stress at a point. Even

better, make a monolithic shell without the need for connections.


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STRUCTURAL MATERIALS Structural materials generally means the walls, roof slabs etc. In this ultra low

cost design of housing low cost natural and agricultural materials are used for all these

walls, roofs etc. But taking strength criteria in to consideration special principle is used

for construction of walls etc.

Generally sandwich type of construction is followed which consists of composite

on ends that are separated by layer of insulation.

Composites: The best low-cost structural materials are composites. Composites are a

combination of distributed fiber reinforcement, lightweight aggregate, and a binding

agent. Ferro-cement is one such composite using metal or synthetic fibers and portland

cement, but there are many others. Fiberglass is a common (but toxic) composite. A

newcomer in fiber composites is papercrete or fibercrete, which is a combination of

pulped paper, or other cellulose-based raw material, and binders such as lime, cement,

and/or clay. Sand adds strength and density to these composites, but lightweight

aggregates could also be used. Any composite material can be used to create shell

structures which we call Composite-Shell construction. Domes 100 ft. in diameter, have

been built using portland cement and glass fibers. Using lesser fibers and binders, more

modest structures can be built. If the fiber composite is applied to both sides of a thick

insulating layer such as straw-clay, perlite cement, or agcrete, a strong "sandwich" is

formed. If the insulation layer is made from a structural honeycomb of lightweight fiber

composite, the strength of the shell is even better.


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Composite materials can be sprayed, or poured, or packed directly onto a reusable

formwork. Simply pour from a bucket, or apply from a scoop, and spread. Fiber

reinforcement options include natural fibers such as wood, bamboo, industrial hemp,

sisal, and jute, for low-tech applications, and synthetic, glass, and steel fibers for high-

tech applications where greater rigidity is desired. Recycled clothing fibers can be used.

Bamboo has been used successfully in place of rebar in many countries for decades.

Wood fiber has been used in Japan for centuries for its strength and beauty. Industrial

hemp fiber has tremendous potential where it is available. It is used for architectural

molding in North America. Discrete bamboo fibers have tremendous strength, exceeding

hemp, and could be the most effective fiber of all if properly processed. Jute is also a

strong natural fiber. All high silica fibers last a long time if protected from rust or rot. Types of composites 1. Fibercrete Composite: 60% Paper + 40% Binder

Binder: 50:50 Portland cement/Hydrated lime

25:25:25:25 Cement, Lime, Clay and Sand

2. Lightweight AgStone Formula:

20 parts chips (Agricultural waste) (Bamboo, Sunflower)

5 parts Clay (With Sand)

5 parts Binders (3 Lime, 2 Cement)

Insulation: Generally insulation is done by the method of honey combing. This creates a

highly insulated very strong structure. A low cost method is to apply a thin 1/2 to 1"

initial layer to a lower portion of the supporting fabric covering a frame in order to begin

the inner shell. Then a honeycomb of material is added on top. Short sections of

lightweight plastic pipe, such as smooth, thin, ABS drainage pipe, are used to make

circular forms. Common flower pots could also work. Slurry is scooped or poured out

over a row of forms, such that 1/2" to 2" of material surrounds the holes and creates a

continuous web of honeycomb. This process is repeated with additional rows of

lightweight circular forms until the structure is covered in the honeycomb. In 24 hours or


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more, the cement will set and harden, the circular forms can be reused if carefully

removed. Holes can be stuffed with balled newspaper or any lightweight, insulating

material, then an outer shell of the desired thickness can be applied. Wasps build paper

houses for their young with honeycomb shapes.

This same method of honeycomb building can be used for walls, too. Only the

pots are placed reversing the direction with each layer or ABS pipe is used rather than

pots. Window frames, door frames, windows, and doors can be cast from this same

material. Frames are placed, then the wall is built around them. Beautiful paper windows,

such as the Japanese are famous for, can be made by stretching paper on both sides of a

window frame with large openings for light. The window is "caulked" into the frame with

a bit more of the same material.

Plastic pipes

Slurry CompositPlastic pipes

Slurry


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DESIGN IDEAS Hexagonal Domes: Our designs employ rooms (often hexagonal) with domed roofs and vertical walls.

The hex room shape increases usable space compared to most other shapes. They can be

nested together to create clusters. The domed roofs are the strongest shape. Vertical walls

are practical for doors, windows, furniture, decoration, and weatherproofing.

The structures consist of a sandwich of:

1. An inner shell of fiber composite placed over a removable form

2. A honeycomb insulation layer made of fiber composite filled with high R value

insulation

3. An outer shell of fiber composite, waterproofed

This building technology is called Composite-Shell construction. Housing can be

built for an extremely low material cost.

The room structure shown above can be combined with others in many ways.

They can be linked, grouped, or nested into various configurations to provide a wide

variety of housing solutions as shown below.

Generally, the plan of house is made such that it looks like cluster of hexagons.

Hexagon shaped rooms are designed to increase the usable space to maximum. Half

hexagons are also used for rooms like study room, mud rooms, alcoves, porches, foyers

and other small area uses.


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Inflatable forms reduce costs: Two layers of plastic sheeting are welded together at their perimeter and stretched

across a tubular form. Air inflates between the layers to create a convex shape. One or

more "wedges" are placed, and then an inch thick of material is poured in place on the

lower portion of the form. Then the honeycomb insulation layer is applied, and then the

outside shell is applied. The forms are removable and reusable. Even doors and windows

(except the glass) can be made from these same composite materials. Our ultimate goal is

for do-it-yourselfers to be able to build one room in a day, or every few days, including

windows, doors, floor, electrical, and modest plumbing.

Social Implications: Building at such a low cost would enable every family to afford housing

without having to take out a mortgage. No longer would families be forced onto the

streets due to the inability to pay rents or mortgages. Nor would families have to

mortgage their lives for 30 years as is common in the West. The social implications

would be tremendous when families can reduce their financial stress. Family violence,

drugs usage, child abuse, and other social ills would be reduced as the pressure to survive

is reduced.

Greater opportunities would arise as families have the time to pursue interests in

education, gardening, music, the arts, yoga, meditation, and spiritual awakening in

general. Families could return to having only one spouse work, allowing one spouse to

anchor the family in culture, home education, inner values, and guidance which have

been abandoned in large measure in the hectic pace of western "civilization".


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FOUNDATION In mild climates, the perimeter foundation only needs to be about 6-8 inches deep.

In cold climates, the foundation should be dug deeper, 12-18 inches. It doesn't have to go

all the way to freezing depth because it will be insulated and heated. It's insulated from

the surrounding earth both to prevent freezing and to retain radiant floor heat (solar

derived). Perlite-cement 6:1 is a good material for subsurface insulation.

For structural integrity the wall foundations may be rammed until the earth at the

perimeter is rock solid. Trials need to be made as to whether a rammed earth perimeter

foundation will last. Historical data would be helpful from those parts of the world where

this may have been tried. Otherwise, conventional poured foundation walls of concrete

with reinforcement are suitable in developed countries.

Gravel foundations, sometimes known as floating foundations, have proved very

successful, even for very heavy walls such as adobe. Most foundations in western

countries are overbuilt. Obviously, the gravel can only come up to grade level without

spilling over, so a rammed earth, stabilized earth (with 10-15% cement), mortared rock,

or concrete layer is needed on top to divert flowing rainwater away from the wall.

One easy way to make the foundation is to make it integral to the wall as it is

being constructed. When the forms have been tilted up and the gravel foundation is at the

edge of the form (as shown to the right), the wall and foundation can be sprayed with

ferro-fiber cement at the same time, making the foundation, wall, and roof in one process.

Whole rooms are created at once with six-sided forms.


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FORM BUILDING Inflatable Forming System: There have been many kinds of inflatable systems for creating buildings, but the

systems which have developed are simple and profound. It does not use large inflatable

balloons, but combines the advantages of both rigid frame and inflatable technologies.

Since it is adjustable, it requires little to no precision and could be made from cheap

bamboo and polyethylene if need be. The inflated volume is drastically reduced, allowing

quick inflation by cheap blowers or even a hand operated bellows, with check valves to

prevent deflation.

First the shape of the frame is defined using lightweight rigid tubing. For this

structure we should use 1/2 inch EMT, electrical conduit. Generally this lightweight

tubing would be suitable for rooms up to 30 feet in diameter. The tubular frame elements

can be 3 or 4 sided and either curved or straight to define virtually any shape.

The tubular frame is braced with straight adjustable elements created from two

tubes which slide inside each other. Emt/pvc which just slide into each other is used. The

frame is wrapped with two layers of polyethylene or other plastic film, heat sealed at the

perimeter. Oiled fabric may also work if sewn tightly at the edges. The double-film

wrapper is oversized to accommodate multiple settings of the dimensions of the frame.

The length of the base to apex arches could be adjustable as well. The oversized wrapper

should fit the largest intended size. It simply wraps over the frame with the extra material

wrapping around underneath the frame.


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The space between the two films is inflated with low pressure air. This provides a

taut surface for applying casting materials such as fibrous cement. This overcomes the

central obstacle to ferrocement which has always been the expensive and tedious nature

of creating one-time-use rebar/mesh surfaces to define a structure.

In the same process whole design is covered with this plastic layer. On this the

main procedure of construction will be started. Firstly the composite is added as layer to

the plastic layer, later on that the insulation is done on the plastic layer and it is again

covered with composite. Roofs and slabs also applied and jointing is done as jointing

methods discussed in engineering principles using ribbons etc.


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EXAMPLES The Gazebo: This gazebo was made with a wooden forming system. The forms were quite a bit

more complex than the forms described earlier in the discussion on form building. This

was an experiment which worked, but the forms were much heavier and more expensive

than we would want. Solid forms were abandoned.

Since this building required no insulation, a lightweight concrete made from

pumice was used. This structure was built by Leslie Feuerborn. Les is an architectural

artist.

One interesting and powerful idea in forming structures with a mold is that the

mold or form can have textured relief cut into it. Various architectural designs can be

incorporated into the mold to create designs in relief when the wall is cast. Notice the

ceiling design. In this case, the relief was further enhanced by antiquing with ordinary

latex paint.


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CONCLUSION

This is an ultra low cost, low weight, high strength housing type. This

design is very environment friendly as the materials used are almost natural and

agricultural products such as the reinforcement used in composites is jute, bamboo etc,

and binders used are also like clay etc. But every thing has its own disadvantages. In this

type of housing there is no scope for future development and extension. This type of

construction cannot be used for multistoried structures. But for housing purposes this is

one of most low cost design ever designed.

REFERENCES

www.planetaryrenewal.org

www.wikipedia.com

AUTHORS

M.Subhash Chandra

2/4 Civil Engineering, GITAM Institute if Technology, GITAM UNIVERSITY, Rushikonda, Visakhaptnam-45. Phone: 9966620348 Email: [email protected]

L.Aditya

2/4 Civil Engineering, GITAM Institute if Technology, GITAM UNIVERSITY, Rushikonda, Visakhaptnam-45. Phone: 9966544961 Email: [email protected]

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Ultra Low Cost Housing