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 #:137
Building Type: Adobe / Earthen House : Adobe block walls
Country: Nicaragua
Author(s): Matthew A. French

Last Updated:
Regions Where Found: Buildings of this construction type can be found in Nicaragua, predominantly used near the Honduras border. Towns close to Costa Rica and the Mosquito Coast area have few adobe dwellings due to their geographic location. This type of housing construction is commonly found in rural areas. Sometimes, adobe is used in urban centres, but not extensively.
Summary:

The plan of this adobe building is a simple rectangle ...

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: 3
Comments: Currently, this type of construction is being built. Influence from its overdeveloped far northern neighbors has led to a wider


Features

 

 

Plan Shape Rectangular, solid
Additional comments on plan shape The building is a rectangle, composed of three rooms; two are 'weather-proof' spaces, and the third a semi indoor-outdoor kitchen.
Typical plan length (meters) 4-9
Typical plan width (meters) 2.8-4
Typical story height (meters) 2.2
Type of Structural System Masonry: Earthen/Mud/Adobe/Rammed Earth Walls: Adobe block walls
Additional comments on structural system Lateral load-resisting system: Adobe walls are relied on to resist lateral loads. The blocks measure 250mm wide, 300mm long and 100mm deep. Mortar joints average 40mm. It is unlikely the roof will work as a diaphragm due to its flexible nature and lack of connection to the walls. Gravity load-bearing system: The adobe walls resist gravity loads and rest on stone rubble foundations.
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 is unknown.
Wall Openings The building has only one door opening on the road elevation due to the need to screen off the dust and noise. The opposing wall has one doorway and one larger break in the wall to allow access to the cooking area. The internal wall to the bedroom has one door opening. There are no windows.
Is it typical for buildings of this type to have common walls with adjacent buildings? No
Modifications of buildings A work area has been added at the rear of the building, but this plays no structural part in the main dwelling being reported on here. This area is merely a roof with one wall on the road side.
Type of Foundation Shallow Foundation: Rubble stone, fieldstone strip footing
Additional comments on foundation
Type of Floor System Other floor system
Additional comments on floor system Compacted earth.
Type of Roof System Roof system, other
Additional comments on roof system wood planks or beams that support slate, metal, asbestos-cement or plastic corrugated sheets or tiles
Additional comments section 2 Typical separation distance between buildings: 4 meters

 

Building Materials and Construction Process

 

 

Description of Building Materials


Structural Element Building Material (s)Comment (s)
Wall/Frame Adobe Characteristic Strength- 3-4 MPa standard block strength. Stabilized blocks up to 8 MPa. Final block strength depends on mixture consistency when pouring blocks. Mix Proportion/Dimensions- Clay 10%-30%, Silt 0%-20%, Sand 50%-70%, Straw to bind The mix changes with site conditions, material availability and builder preference.
Foundations Stone and mortarMix Proportion/Dimensions: Field stones and mud Foundation types vary widely.
Floors Compacted earth Mix Proportion/Dimensions: 5-10% chopped straw to bind earth Relaid/ relevelled as required
Roof Timber with iron sheeting Mix Proportion/Dimensions: 100mm X 40mm sawn timber rafters laid on unsawn timber top plate
Other

Design Process


Who is involved with the design process? Other
Roles of those involved in the design process Only local traditional knowledge is used in these constructions. The role of architects is minimal to none.
Expertise of those involved in the design process

Construction Process


Who typically builds this construction type? Owner
Roles of those involved in the building process
Expertise of those involved in building process
Construction process and phasing The site is cleared. The mud block ingredients are mixed and placed in a wet mold. This is compacted and turned out to dry. While the blocks are drying, the site is further prepared. After four weeks, and several rotations of the drying block, the block is ready for final placement. The wall is constructed by simply laying one block on another with mud mortar between until the desired height is reached. The timber roof framing is laid and the corrugated iron material nailed in place. 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)No one
Additional comments on maintenance and building condition

Construction Economics


Unit construction cost US $ 20/m2.
Labor requirements Typically, adobe dwellings of this size take between 1-3 months to construct. The bricks alone must be left to dry for 3-4 weeks in the sun. As there several people on site - family, friends, and community helpers - adobe is a relatively quick and informal construction method for Nicaragua.
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy The house is occupied by one family. It is used as a base from which the mother and daughter make food to sell on local buses as their source of income. During the evening, the whole family is present.
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)
Additional comments on economic level of inhabitants House Price/Annual Income (Ratio) 1:1 or better
Typical Source of Financing Owner financedPersonal savingsInformal network: friends or relatives
Additional comments on financing
Type of Ownership RentOwn 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
197212.400N
198511.725N
200411.424N
200511.198N
6.2 6 (MMI)
6 6 (MMI)
6.9 6 (MMI)
6.6 6 (MMI)

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type Wall: The walls will crack in shear from lateral in-plane loads, or will fall in or out due to face-loads. In both cases, roof collapse may follow due to loss of wall support. Roof: The roof collapses due to lack of wall support and poor connections.
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.N/A
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.FALSE
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 No irregularities
Horizontal irregularities typically found in this construction type No irregularities
Seismic deficiency in walls The adobe walls have limited tension resistance under seismic loads.
Earthquake-resilient features in walls
Seismic deficiency in frames
Earthquake-resilient features in frame
Seismic deficiency in roof and floors The roof is poorly connected to the walls, and these poor connections ensure that it can not be counted on to act as a rigid diaphragm for the transfer of loads.
Earthquake resilient features in roof and floors The roofing material is lightweight, so the risk of injury from roof collapse is minimized.
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
Walls 1. Bamboo: Several researchers have been involved with using internal horizontal and vertical bamboo, in a fashion similar to reinforced concrete masonry walls. 2. Timber ring beam: This helps to hold the walls together and facilitate transfer of loads from the roof to the walls. 3. 'Improved Adobe' has long been promoted to make adobe buildings more robust under seismic activity. The 'system' does not utilise another material, but focuses on the design and planning of adobe buildings by limiting opening sizes, plan dimensions, wall lengths and heights, and roof weight
Roof Adequate connections to a top timber or concrete ring beam and stronger connections in the framing itself will help the roof act as a diaphragm. Galvanized sheet metal is now common and helps reduces high loads. For thermal and aesthetic reasons, how ever, clay tile continues to be used.

Additional comments on seismic strengthening provisions The bamboo strengthening scheme is not used in Nicaragua, but is presented here as an option for making Nicaragua buildings safer.
Has seismic strengthening described in the above table been performed? Bamboo: Yes, it has been implemented in Peru with successful structural results, but unsuccessful local adoption of the concept. The system has not been used in Nicaragua. Timber ring beam: These are common now but often limited finances ensure they are out of reach for many in Nicaragua. 'Improved Adobe': Some principles are used, such as small openings and walls, but others are not evident, such as buttresses.
Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? All work done was only as part of the mitigation efforts.
Was the construction inspected in the same manner as new construction?
Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? Technical assistance was used in the Bamboo implementation. Timber ring beams are often incorporated in new constructions by the occupants.
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? The bamboo system and timber ring beams have proven structurally successful in earthquakes.
Additional comments section 6

 

References

Guidelines for earthquake resistant non-engineered construction IAEE National Information Center of Earthquake Engineering, IIT Kanpur, India 2004


An improved means of reinforcing adobe walls- external vertical reinforcement Dowling,D. & Samali,B. & Jianchun,L. Sismo Adobe, Lima, Peru 2005


Adobe and rammed earth buildings: design and construction McHenry,P. John Wiley and Sons, Canada 1984


Building with earth: a handbook Norton,J. Intermediate Technology Group, Warwickshire, UK 1986


Earthquake database search, www.ngdc.noaa.gov National Geophysical Data Centre, Date accessed: 15/3/2006


Authors



Name Title Affiliation Location Email
Matthew A. French Architecture, Victoria University of Wellington 15 Landcross Street, Wellington 4001, NEW ZEALAND emailformatthew @hotmail.com

Reviewers


Name Title Affiliation Location Email
Andrew W. Charleson Associate Professor School of Architecture, Victoria University of Wellington Wellington 6001, NEW ZEALAND andrew.charleson@vuw.ac.nz