Description

The World Housing Encyclopedia (WHE) Report Database contains 130 reports on housing construction types in 43 seismically active countries. Each housing report is a detailed description of a housing type in a particular country. The description is prepared from a number of standard closed-ended questions and some narrative that have been provided by report authors. Each report has five major categories including architectural and structural features; Building Materials and Construction Process; Socio-economic Issues; Past Performance In Earthquakes, Seismic Features and Vulnerability; and Retrofit. All of the housing reports in this database have been contributed by volunteers. If you are interested in writing a housing report please contact the WHE Editorial Board.

About

The World Housing Encyclopedia (WHE) is a collection of resources related to housing construction practices in the seismically active areas of the world. The mission is to share experiences with different construction types and encourage the use of earthquake-resistant technologies worldwide. The technical activities of the WHE are steered by an international team of 22 professionals specializing in different aspects of seismic safety of buildings and structures. They bring relevant experience from 16 seismically active countries across the world. For more information about the World Housing Encyclopedia, visit http://www.world-housing.net/.

General Information

 

Report #:104
Building Type: Adobe / Earthen House
Country: IRAN
Author(s): Mehrdad Mehrain
Farzad Naeim
Last Updated:
Regions Where Found: Buildings of this construction type can be found in the Middle East. This type of housing construction is commonly found in both rural and urban areas.
Summary:

This building type is typically one or two stories and ...

Length of time practiced: More than 200 years
Still Practiced: Yes
In practice as of:
Building Occupancy: Single dwelling
Typical number of stories: 1
Terrain-Flat: Typically
Terrain-Sloped: 4
Comments: Adobe construction is widespread throughout Iran, and is used both by wealthy families in luxury residences as well as poor fami


 

Features

 

 

Plan Shape Rectangular, with an opening in plan
Additional comments on plan shape Small windows, one entrance door and one entry for each room.
Typical plan length (meters) 12
Typical plan width (meters) 12
Typical story height (meters) 3
Type of Structural System Masonry: Earthen/Mud/Adobe/Rammed Earth Walls: Adobe block walls
Additional comments on structural system The vertical load-resisting system is earthen walls . The roofs are usually adobe domes or cylindrical arches, supported on adobe walls. Sometimes flat adobe roofs with wood joists are used (as described in section 1.9, if these buildings are built on hillsides, the ground floor of one building can be the roof for another.) . The lateral load-resisting system is earthen walls . The lateral load-resisting elements are adobe walls, typically 3 m high, 4 m wide and 0.80 m thick. The walls do not have any additional system (such as crown beam or pilasters) to restrain their out-of-plane movement. That is one reason why the buildings are so vulnerable in earthquakes. If the walls move out of plane, the roof loses its support, and collapses .
Gravity load-bearing & lateral load-resisting systems
Typical wall densities in direction 1 >20%
Typical wall densities in direction 2 >20%
Additional comments on typical wall densities The typical structural wall density varies from 10% to 35%. The walls are very thick, typically +/- 70-80 cm.
Wall Openings Small windows, one entrance door and one entry for each room. Opening area is about 30 percent of total wall area .
Is it typical for buildings of this type to have common walls with adjacent buildings? Yes
Modifications of buildings No modifications are made to the building .
Type of Foundation Shallow Foundation: Wall or column embedded in soil, without footingShallow Foundation: Rubble stone, fieldstone strip footing
Additional comments on foundation
Type of Floor System Vaulted masonry floorOther floor system
Additional comments on floor system
Type of Roof System Vaulted masonry roofRoof system, other
Additional comments on roof system The roofs (and walls) typically have a 5 cm (2 inch) layer of straw reinforced mud to provide protection against rain .
Additional comments section 2 The typical separation distance between buildings is more than one meter, if not connected to adjacent buildings.

 

Building Materials and Construction Process

 

 

Description of Building Materials


Structural Element Building Material (s)Comment (s)
Wall/Frame Adobe is used to make walls. No information is available on this.
Foundations
Floors
Roof
Other

Design Process


Who is involved with the design process? None of the above
Roles of those involved in the design process
Expertise of those involved in the design process No special expertise . None .

Construction Process


Who typically builds this construction type? Other
Roles of those involved in the building process
Expertise of those involved in building process No special expertise . None .
Construction process and phasing Sun dried adobe units are used to build walls and roof. A 2-inch layer of straw-reinforced mud covers the walls and roof for rain protection. Every 4 to 6 years, this layer is washed away from the roof and requires replacement. The construction of this type of housing takes place in a single phase. Typically, the building is originally designed for its final constructed size.
Construction issues

Building Codes and Standards


Is this construction type address by codes/standards? No
Applicable codes or standards
Process for building code enforcement

Building Permits and Development Control Rules


Are building permits required? No
Is this typically informal construction? Yes
Is this construction typically authorized as per development control rules? No
Additional comments on building permits and development control rules

Building Maintenance and Condition


Typical problems associated with this type of construction
Who typically maintains buildings of this type? Owner(s)
Additional comments on maintenance and building condition

Construction Economics


Unit construction cost $20/m2 (this is a rough estimate. A lot of people build their own houses, using their own dirt to make adobe blocks.) .
Labor requirements It takes about 100 days for 2-3 persons (200-300 person days) to complete the construction.
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy Just one family, possibly with married son and daughter-in-law, lives in each unit .
Number of inhabitants in a typical building of this construction type during the day <5
Number of inhabitants in a typical building of this construction type during the evening/night <5
Additional comments on number of inhabitants
Economic level of inhabitants Very low-income class (very poor)Low-income class (poor)Middle-income class
Additional comments on economic level of inhabitants The ratio of price of each housing unit to the annual income can be 10:1 for very poor and poor families, and 20:1 for middle class families .
Typical Source of Financing Owner financedPersonal savingsInformal network: friends or relativesSmall lending institutions/microfinance institutions
Additional comments on financing
Type of Ownership Own outrightOwn with debt (mortgage or other)
Additional comments on ownership
Is earthquake insurance for this construction type typically available? No
What does earthquake insurance typically cover/cost
Are premium discounts or higher coverages available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features? No
Additional comments on premium discounts
Additional comments section 4

 

Earthquakes

 

 

Past Earthquakes in the country which affected buildings of this type


YearEarthquake Epicenter Richter Magnitude Maximum Intensity
1990Manjil
1997Ardekul
2003Bam
7.7
7.3
6.6

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type Iran has a long history of devastating earthquakes that have affected adobe structures. In the 2003 Bam earthquake, over 40,000 people died; in 1997 over 1,568 people died and in the 1990 earthquake in Manjil over 40,000 people died. In the Bam area, there have also been other significant earthquakes: in the Gisk-Zarand 1977 earthquake--665 people were killed; in the 1981 Golbaf earthquake--between 1,000 and 3,000 people were killed; in the 1981 Sirch earthquake- -1300 people killed. Many people were killed in adobe structures .
Additional comments on earthquake damage patterns

Structural and Architectural Features for Seismic Resistance


The main reference publication used in developing the statements used in this table is FEMA 310 “Handbook for the Seismic Evaluation of Buildings-A Pre-standard”, Federal Emergency Management Agency, Washington, D.C., 1998.

The total width of door and window openings in a wall is: For brick masonry construction in cement mortar : less than ½ of the distance between the adjacent cross walls; For adobe masonry, stone masonry and brick masonry in mud mortar: less than 1/3 of the distance between the adjacent cross walls; For precast concrete wall structures: less than 3/4 of the length of a perimeter wall.
Structural/Architectural Feature Statement Seismic Resistance
Lateral load pathThe structure contains a complete load path for seismic force effects from any horizontal direction that serves to transfer inertial forces from the building to the foundation.FALSE
Building Configuration-VerticalThe building is regular with regards to the elevation. (Specify in 5.4.1)TRUE
Building Configuration-HorizontalThe building is regular with regards to the plan. (Specify in 5.4.2)TRUE
Roof ConstructionThe roof diaphragm is considered to be rigid and it is expected that the roof structure will maintain its integrity, i.e. shape and form, during an earthquake of intensity expected in this area.FALSE
Floor ConstructionThe floor diaphragm(s) are considered to be rigid and it is expected that the floor structure(s) will maintain its integrity during an earthquake of intensity expected in this area.FALSE
Foundation PerformanceThere is no evidence of excessive foundation movement (e.g. settlement) that would affect the integrity or performance of the structure in an earthquake. TRUE
Wall and Frame Structures-RedundancyThe number of lines of walls or frames in each principal direction is greater than or equal to 2.TRUE
Wall ProportionsHeight-to-thickness ratio of the shear walls at each floor level is: Less than 25 (concrete walls); Less than 30 (reinforced masonry walls); Less than 13 (unreinforced masonry walls);TRUE
Foundation-Wall ConnectionVertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation.N/A
Wall-Roof ConnectionsExterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. FALSE
Wall OpeningsTRUE
Quality of Building MaterialsQuality of building materials is considered to be adequate per the requirements of national codes and standards (an estimate). FALSE
Quality of WorkmanshipQuality of workmanship (based on visual inspection of a few typical buildings) is considered to be good (per local construction standards).FALSE
MaintenanceBuildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber).FALSE

Additional comments on structural and architectural features for seismic resistance
Vertical irregularities typically found in this construction type Other
Horizontal irregularities typically found in this construction type Other
Seismic deficiency in walls They are weak in the out of plane direction. The walls tips over or bend outwards.
Earthquake-resilient features in walls There are no earthquake resistant features. If the adobe walls can be kept in place, the seismic performance of the building will improve significantly .
Seismic deficiency in frames
Earthquake-resilient features in frame
Seismic deficiency in roof and floors It is made of weak materials. If the walls move out of plane, the roof collapses.
Earthquake resilient features in roof and floors The roof consists of arches and domes which provide integrity.
Seismic deficiency in foundation
Earthquake-resilient features in foundation

Seismic Vulnerability Rating


For information about how seismic vulnerability ratings were selected see the Seismic Vulnerability Guidelines

High vulnerabilty Medium vulnerabilityLow vulnerability
ABCDEF
Seismic vulnerability class o

Additional comments section 5

Retrofit Information

 

 

Description of Seismic Strengthening Provisions


Structural Deficiency Seismic Strengthening
Weak walls In other countries, particularly Peru, add reinforced concrete, or add rope stitching
Weak walls Dimensional constraints, bamboo reinforcement (Peru) or reinforced concrete overlay.

Additional comments on seismic strengthening provisions
Has seismic strengthening described in the above table been performed? None in Iran .
Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? Not applicable .
Was the construction inspected in the same manner as new construction? Not applicable .
Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? Not applicable .
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? Not applicable .
Additional comments section 6

 

References

Authors



Name Title Affiliation Location Email
Mehrdad Mehrain Vice-President URS Corporation 911 Wilshire Blvd., Los Angeles CA 90017, USA Michael_Mehrain@URSCorp.com
Farzad Naeim Vice President John A. Martin & Associates 1212 South Flow er Street 4th Floor, Los Angeles CA 90015, USA farzad@johnmartin.com

Reviewers


Name Title Affiliation Location Email
Marcial Blondet Professor Civil Engineering Dept., Catholic University of Peru Lima 32 , PERU mblondet@pucp.edu.pe