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Adobe walls supporting rough timber framed roof with corrugated iron sheeting

1. General Information

Report #: 137

Report Date: 26-05-2007


Housing Type: Adobe / Earthen House

Housing Sub-Type: Adobe / Earthen House : Adobe block walls

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 with three rooms. Adobe as a material is very weak under seismic loads, which is the main issue which concerns this building type. Also, the roof does not have sufficient eaves to protect the adobe walls, which has resulted in the dislodging of the exterior plaster. This has eroded the walls, further reducing their structural strength. Adobe is commonly used in Nicaragua, as it is both affordable and accessible, but it is being replaced by more 'modern' materials, such as concrete block and red fired brick.

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

2. 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

3. Buildings 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 mortar Mix 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

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:

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

4. 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:

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