ultra low cost housing

Ultra Low-Cost Housing

M.Subhash Chandra

3/4 CIVIL Engineering

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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INTRODUCTIONThe 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 PRINCIPLESBending 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.

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

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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.

STRUCTURAL MATERIALSStructural 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.

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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.

Types of composites1. 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)

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

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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 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.

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Plastic pipes

Slurry Composite Plastic

pipes

Slurry


DESIGN IDEASHexagonal 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.

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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FOUNDATIONIn 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 BUILDINGInflatable Forming System:

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 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.

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.

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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.

EXAMPLESThe 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.

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.

AUTHORS

M.Subhash Chandra

3/4 Civil Engineering,

GITAM Institute if Technology,

GITAM UNIVERSITY,

Rushikonda, Visakhaptnam-45.

Phone: 9966620348

Email: [email protected]

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