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Choosing Shelter Plans for Hazardous Areas |
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By Patti Stouter, Owen Geiger and Kelly Hart |
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In many parts of the world disaster-relief shelters need to survive earthquakes and hurricanes. Structures should also function well during the different seasons. But shelters must be inexpensive and quick to build. They must also be easy to remove when the displaced people have better homes.
A strong bond or ring beam helps to keep buildings together during earthquakes. The strength of an earthbag wall is, like adobe, related to its shape. Compact layouts are stressed by earthquakes less than long ones. Symmetrical layouts can be shaken less than irregular ones. Curving walls of earthbag are the strongest shapes with little or no reinforcement. Straight walls of earthbag can be strengthened with corner or internal bracing and earthbag buttresses. Traditional roofs with small overhangs can be hurricane resistant. Fasten them securely to heavy earthbag walls and using heavy metal straps on top of corrugated metal. Temporary tarp roofs on earthbag walls can be fastened well enough to survive high winds. Carefully nail them on all sides to wood plates embedded in the walls.
Use the materials that can be purchased cheaply or scavenged from debris. This will keep your costs down. All of these materials can be used for earthbag construction. Many of them provide reinforcement needed to resist earthquakes and hurricanes: Metals: ½" (12 mm) diameter rebar, 2- 5' (60 cm- 1.5 m) lengths 4' (120 cm) or longer pieces of metal pipe 1-1/2" x 4" (4-10 cm), or other size, hollow rectangular section steel tubing 8- 12" (20- 30cm) wide strips of corrugated metal roofing at least 4' (120 cm) long hurricane straps, door or shutter hinges, security doors, window frames, nails plasterer's galvanized lath or galvanized chicken wire
Wood: 2- 4" (5- 10 cm) diameter poles 2x4s, 2x6s or 2x8s (5x 10, 15, or 20 cm) lumber plywood scraps 8- 12" (20- 30 cm) wide wood or wicker shutters Plastics:Tarpaulins, poly or nylon fishnet plastic plasterer's mesh, baling twine Natural materials: Soil that includes some clay gravel vetiver thatch, reeds rice hulls or straw for insulation branches for wattle The keys to safe earth buildings (including earthbag shelters) are good quality construction, robust layout, and good seismic reinforcement.
Right: Earthbag building in Africa Earthbag walls are really big adobe units. They have extra vertical strength to carry weight from being tamped. They have greater horizontal tensile strength from the interlocking bags and barbed wire. But in areas with high risk of earthquakes, extra reinforcement should be added to earthbags. Earthbag can be reinforced for seismic areas in the same ways that work to protect adobe buildings. The bases of walls, corners, and the tops of walls are the most important areas to reinforce. Another way to make adobe or compressed earth blocks strong uses vertical and horizontal ropes or rods of bamboo. Few buildings in warm climates have a reinforced concrete footing. It may also be important to tie the building together close above its base of stone or rubble footings for earthquake safety. Earthbag already has a lot of horizontal strength from barbed wire. Rebar or strapping or rope helps to tie earthbag buildings together vertically. Then with a bond or ring beam anchored to the walls, they become stiffer and stronger. The materials that change the shapes of earthbag structures the most are cement and steel. Simple rectangular shapes work with rebar hammered through bag layers or sections of pipe and metal lath at corners. If little metal is available shelters can have overlapping buttresses at the corners. This takes more soil and bags and more construction time. The list that follows explains some of the construction and shape alternatives:  'CLEAN' CORNERS: Materials Required One type of corner reinforcement:
One type of opening reinforcement:
And one type of bond beam:
BUTTRESSED CORNERS: Materials Required One type of opening reinforcement:
One type of bond beam:
If little or no cement and steel are available, curving walls will provide the greatest strength. Temporary structures with fewer reinforcements must be carefully shaped.  Materials Required One type of bond beam:
Building shapes that are compact rather than stretched out more easily resist earthquakes. Those proportioned like squares or circles are stronger than narrow or bent shapes.
But circular buildings may not fit in with peoples' traditions and ideas of home. Sometimes for transitional housing they are considered too odd, or too difficult to extend with additions.
Even slightly bowed walls with corner buttressing have been shown to have strength similar to circular walls.
Earthbag has been widely used to make earthen domes, both with cement stabilization or without. These are both hurricane and earthquake resistant. But in wet climates unstabilized domes require sophisticated waterproofing and careful maintenance. If leaks develop in earthbag domes that were built without cement stabilization, they can become saturated and fail. Although they are very inexpensive, they require skill to build. Because of maintenance issues, earthen domes may not be the best choice for emergency shelter in rainy climates.
Lighter walls and roofing or temporary tarps can quickly be added between separate earthbag structural rooms. Basic Dimension Standards
Robust layout for earth construction walls not too high and openings spaced out well from each other and from corners. Simple shelters of 15" (38 cm) wide bag walls can be built to 7'- 9' (2.1 - 2.7 m) wall heights. Higher walls can be used in areas without earthquakes. But shelters don't need very high walls.
Lintels above doors or windows are very strong if they are part of the bond or ring beam. If a lintel is separate from the bond beam, it should extend into the walls at least 16" (40 cm) each side of an opening. Earthquake resistance can also be improved by the type of grading used. A structure with a little excavation behind and a little fill in front is best. A shelter cut deeply into a slope or placed right on the edge of a steep slope is less safe in earthquakes. Until detailed engineering tests of specific earthbag reinforcement techniques prove that there are lower dimensional requirements for earthbag, it is best to follow standard adobe practice for safe dimensions: Adobe walls can be 10 times as high as their width. 8 times their width may be safer in seismic areas. A 15" (38cm) wide earthbag wall is very strong at 9' (2.7 m) height. If retaining walls beneath floor level require a total wall height of more than 10' (3 m) the lowest portion can be built of larger bags for a wider wall section. If two window or door openings are necessary in a single wall, they can be spaced 18" (50 cm) from each side of an intersecting wall or a pier that extends 24" from the wall. This would require a wall at least 14'3" (4.3 m) long to fit 2 windows. Wall HeightsWith a cement bond beam earthbag walls can be lower. For good earthquake resistance it is important that a ring beam be continuous and bridge across the doorway. The wall height must match the height of the doorway plus the bond beam. What the bond beam is made of is important. These diagrams show a door height of 6'8" or 203 cm. If doors are lower, walls can be lower.
7'4" (2.2 m) minimum wall height Bond beam of reinforced concrete 6" x 16". Hot humid or comfortable regions. Best earthquake resistance.
Bond beam of wood, tubular steel, or corrugated metal. Hot humid areas near sea level, or comfortable areas above. Good earthquake resistance.
Windows must also fit beneath the bond beam. Low shelter eaves walls are really only good where the climate is comfortable. In these places rooms do not need breezes for comfort during most of the day.
7'4" at doors (2.2 m) and 6'1" at eaves (1.85 m) min. Reinforced concrete lintel 6" h x 16"w (15x38 cm) over door. Bond beam of wood, tubular steel, or corrugated metal tied well to door lintel. Comfortable regions. Good earthquake resistance. Shelter plans for areas with low earthquake risk can have shallow sloped gable walls of earthbags. Small shelters with shed roofs are simple to build with earthbag walls that step down like this to low roof eaves. But it takes a cement bond beam to tie this kind of shelter together well. If cement is not available, in high seismic risk areas do not step a wall up more than 2 bag courses or 10" (25 cm) total.
Separate bond beams on each corner segment. Single layer lintels above door and window openings. Low earthquake resistance.
Because shelters can have walls lower than standard doorway heights, people may want to plan structures like that shown above. Separate wall pieces with lightweight connections across window or door openings are not very well braced. In an earthquake this kind of wall can vibrate more and is more likely to fail. RoofingTarpaulin roofing is cheap and quick. But in wet climates the earthbag wall needs the tarp to hang down at least 24" (60 cm). Or an additional plastic strip can cover the top of the wall and hang down at least 12" (30 cm) outside to protect the top of the wall.
Little wood or metal. Use a vertical pole during storms to keep rainwater from ponding on tarp.
Tarp & rafters Some wood or metal for roof rafters, long enough to span the room.
Short wood or metal for rafters, long ridge pole. Wood and or corrugated metal needed for gable wall construction Best against leaking and for traditional appearance.
When shelters are first built they can be very overcrowded. Good layouts can seem unimportant. But shelters often become transitional or permanent housing. If they are well designed and located families can be healthy in them when they become less crowded. Double shelters with tents between sturdier earthbag structures. When some people return to repaired homes or find other places to live, the ones left will be less crowded. Many cultures in tropical areas are very group-oriented. Families can include grandparents, aunts and uncles as well as neighbors and friends. The relationship between the entrances to shelter rooms will either strengthen or weaken these families. Entrances near each other may make people safer in shelters.
In many warm regions life is lived outdoors. The edges of yards are more important than building walls. Home may be the space within walls or hedges. Open spaces that people feel they 'own' will be cleaner and safer.
Aid organizations may want multiple room shelter units. These share walls and need less building. With multiple shelters it can be harder to keep rainfall out of entry porches. It is important for people to have dry outdoor spaces to use. People who need a shelter will feel strongly about some unit shapes and some types of cluster layouts. Their families will have to put up with how people act in them for a long time. Ask people what they think. Black and white sketches of these layouts and groupings are included in the appendix.
Find out how many rooms are needed for the families. Duplex units are good. They can be united in the future to a four room house. Or a wall could be removed to turn a room into a porch. Separate duplex units can be added to later. If simple shelter rooms are 7' or 8' x 12' (2.1- 2.4 m x 3.7 m) or more they can also be split for most use with tarps for more privacy. The location of doors is important to most people. The way they enter, and the boundaries between public and private spaces are often emphasized. Doors may be arranged to limit views into the house. Doors or porches or front walls are often ornamented in small homes. People who spend much time outside often turn their buildings and yards very carefully to take catch or escape breezes or sunlight. Compass directions can also have meanings that are still important to displaced people.
In cool climates many peoples have doorways that face toward the east and the equator. This lets sunlight in to warm the dooryard and the house. In the morning people want their home and porches to warm up in the coolest part of the day.
In warm climates people are careful not to face their doorway west. The afternoon sun can overheat both the entry area and building. Doors and window openings in hot areas often face the breeze, and may face away from the equator and the sun. In warm regions the front door area may be where people sit and work. Grouping shelter entrances to face each other can help people make friends. A small groups of shelters with entrances that face each other can help people to get a few closer friends in a very stressful place. People will watch what happens in a shared outdoor space. It can be much safer than a space that seems like it belongs to no one. Shared services (like bathrooms or water pipes that are located in small clusters also brings people together. Each of the groupings and layouts on the pages that follow will influence the people of the camp in important ways. People who live there should be able to help shape the camp. Separate Unit Groupings
Impersonal environment without any sense of public space. Perceived as neat and equal or fair by designers, but dehumanizing by residents.
Small groups mildly defined. Little sense of public space ownership. Interactions allowed.
Cluster Groups clearly defined. Strong sense of public space ownership. Interaction encouraged. Multiple Unit Grouping
Door direction determines whether interaction is required or discouraged. Moderate ventilation. Must drain between buildings.
Small group interaction encouraged. Moderate ventilation possible. Can drain to the rear or sides.
Simple quad Small groups, Limited Interaction encouraged. Limited ventilation possible. Must drain to the sides.
Groups clearly defined, interaction required. Moderate ventilation. Can drain to rear or sides. Plans, Details and Advice This website provides information about shelter plans using earthbags that are available for free in different room arrangements and unit sizes. The techniques for construction and types of materials used are only mentioned in this booklet. Details are more fully described and discussed on the website. Those who are new to earthbag construction should carefully read the information here , and possibly search the site at www.earthbagbuilding.com for descriptions of techniques and processes as well as videos. If you are involved in or planning an earthbag project for Haiti, request a membership in the Earthbag Structures private shelter blog to discuss issues and get additional help. Additional Information:A worthwhile manual for basic earthbag construction and earth plastering techniques is Earthbag Building : The Tools, Tricks and Techniques by Kaki Hunter, Donald Kiffmeyer, New Society Publishers: 2004. This is available in English as a pdf ebook at http://www.ebooks.com/ebooks/book_display.asp?IID=256395 . Few books include information about Haitian styles of building. Haitian Wisdom for Aid Buildings, by Patti Stouter has 29 pages about Haitian types of houses and the cultural forces that shape them. It also contains a list of web sites and articles about Haitian vernacular architecture. No information about a culture is an adequate replacement for letting project recipients or emigrants familiar with the project area review and modify the plans. This step is probably the single most important factor in successful aid projects. Appendix: Survey Sketches |
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Earthbag is an inexpensive but very strong building technique. It does not require much imported material. But, like the adobe block techniques it resembles, it requires some understanding to make wise plan choices. Cheap building shapes fit the materials available to use in buildings. The wall heights and kinds of roofing supports also fit the materials. 
Keep shelter floors dry during rainy seasons or flooding as well as hurricanes. Earthbags make a good foundation for less waterproof construction. They can shape a seat wall inside a tarp shelter to keep water from blowing or running inside. 
Good quality construction means build walls plumb, use strong bags, and use good soil. Bags cannot be left out in the sun for more than a few weeks before covering. Make sure your soil will hold up the building. Use good building soil. Soil can have less clay than what is needed for adobe. But good soil for earthbags must not be too silty, have too much sticky clay, or be only sand. 
One successful type of adobe wall reinforcement uses cement plastered wire mesh. This shapes an exterior upper ring and corners and intermittent columns. 
Curved shapes also are much stronger than straight. Simple circles are easier to build than rectangles with corners. 
They may be good for temporary shelters. Curved building walls need less reinforcing. They can be a good choice for shelters if displaced people can accept them. 
Small curves at corners can also strengthen walls. Walls that curve at a radius of between 3' and 15' (1m and 4.5 m) are much stronger than straight walls. 
If long or bent shapes are needed where little reinforcement material is available, build separate compact shapes. 
Choose the kind of shape to use for the materials you have. But safe dimensions are important. 
Walls must have at least 36-39" (1 m) from each opening to a corner. A shelter with a single opening in each wall needs walls at least 8' (2.4 m) long. This is for a 24" (60 cm) wide window. A wall with a door should be at least 8'6" (2.6 m) long for a 30" (75 cm) wide doorway. 
8' at doors (2.4 m) and 7'2" at eaves (2.2 m) min. 
6'8" (2.03 m) minimum wall height 
Tarp only 
Tarp gable 
Shelters built at camps may not be able to have walls to separate outdoor areas. But shelters can be arranged to show the edges of spaces. The sides of shelters can define boundaries between groups. These can provide a sense of ownership of the space between them.
Grid: No groups defined. 
Offset 
Integrated or back to back duplex 
Side by side duplex 
Clustered quad