Report: 91

Building Type: EMSB1- single storied brick masonry house generally with GI roof

Country: Bangladesh

Author(s): Mehedi Ansary

Last Updated:

Regions Where Found: Buildings of this construction type can be found in all parts of Bangladesh. This type of housing construction is commonly found in both rural and urban areas.

Summary: This is a one-story brick masonry house of fired bricks with cement or lime mortar; roof is either GI sheet or other material. These houses can be seen all over Bangladesh. During the 1918 Srimangal, 1930 Dhubri and some recent earthquakes, these type of houses suffered heavy damage. Houses with a continuous lintel suffered less.

Length of time practiced: 76-100 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Single dwelling

Typical number of stories: 1

Terrain-Flat: Typically

Terrain-Sloped: 3

Comments:

Plan Shape: Rectangular, solidL-shape

Additional comments on plan shape: Mostly L-shaped, sometimes rectangular.

Typical plan length (meters): 3-5

Typical plan width (meters): 2-4

Typical story height (meters): 2.8

Type of Structural System: Masonry: Unreinforced Masonry Walls: Brick masonry in lime/cement mortar

Additional comments on structural system: The vertical load-resisting system is earthen walls. Traditionally, 10 inch wall is used as load bearing walls. But sometimes poor people use 5 inch wall. Poorer construction do not have any kind of plaster. The lateral load-resisting system is earthen walls. Sometimes there is a continuous lintel, sometimes none. In earthquake prone areas like Chittagong, Sylhet etc. approximately 50% private housing units have continuous lintel. But on the government buildings, the percentage is much lower.

Gravity load-bearing & lateral load-resisting systems: Tie columns are not used.

Typical wall densities in direction 1: 15-20%

Typical wall densities in direction 2: 15-20%

Additional comments on typical wall densities: The typical structural wall density is up to 20 %. 15 - 20%.

Wall Openings: At least three for a single room (two windows and one door). The buildings generally comprise of two to three rooms. The inner and outer rooms have at least two doors. Opening per wall is around 20%. Doors and windows are located in the middle of the wall.

Is it typical for buildings of this type to have common walls with adjacent buildings?: No

Modifications of buildings:

Type of Foundation: Shallow Foundation: Wall or column embedded in soil, without footing

Additional comments on foundation: Stepped brick foundations with cement mortars are used. Generally foundation bottom lies 2 to 3 ft below GL.

Type of Floor System: Other floor system

Additional comments on floor system:

Type of Roof System: Roof system, other

Additional comments on roof system: GI roofs with purlins.

Additional comments section 2: In the villages this type of housing may be located several 100 meters apart. When separated from adjacent buildings, the typical distance from a neighboring building is 2 meters.

Who is involved with the design process? Owner

Roles of those involved in the design process: Owners are the architect and masons are the engineer for this type of housing.

Expertise of those involved in the design process: They do not have a large role, but masons can be trained by the engineers according to the code guideline for construction.

Who typically builds this construction type? Mason

Roles of those involved in the building process: The house owners hire masons to build these houses. Sometimes masons live in similar houses.

Expertise of those involved in building process: No formal training. Masons are trained by their seniors.

Construction process and phasing: - trench line is planned - excavate 2 to 3 ft deep trench - 6 inch thick sand layer - lay brick and use cement mortar to join them The construction of this type of housing takes place in a single phase. Typically, the building is originally not desig

Construction issues:

Is this construction type address by codes/standards? Yes

Applicable codes or standards: This construction type is addressed by the codes/standards of the country. Bangladesh National Building Code. The year the first code/standard addressing this type of construction issued was 1993. BNBC 1993.

Process for building code enforcement: There is no enforcement of building codes for this type of construction.

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: There are no guidelines for this type of housing. No prior approval is required.

Typical problems associated with this type of construction:

Who typically maintains buildings of this type? Owner(s)

Additional comments on maintenance and building condition:

Unit construction cost: Total project: US Dollar 50/sq m.

Labor requirements: The labor requirements for a typical house of about 30 to 50 sq.m are about 100 to 120 man-days.

Additional comments section 3:

Patterns of occupancy: As the joint family tradition is strong in the rural areas, an extended family occupy the housing unit. Typically, the families comprise of a father and two-three sons. As the family further expands, the sons families occupy independent units.

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: 5-10

Additional comments on number of inhabitants:

Economic level of inhabitants: Middle-income classHigh-income class (rich)

Additional comments on economic level of inhabitants: The middle class housing unit roughly costs USD 1,000, on the other hand the rich housing unit costs USD 1,500 to 2,000. Ratio of housing unit price to annual income: 1:1 or better

Typical Source of Financing: Owner financedPersonal savingsSmall lending institutions/microfinance institutions

Additional comments on financing:

Type of Ownership: RentOwn outright

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:

Damage patterns observed in past earthquakes for this construction type: During the 1897 Assam earthquake, almost 90% of this type of structure suffered some kind of damage.

Additional comments on earthquake damage patterns:

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.

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: Weak from earthquake point of view; sometimes there are no plaster; lack of lintel bands; no measures to strengthen the corners.

Earthquake-resilient features in walls:

Seismic deficiency in frames:

Earthquake-resilient features in frame:

Seismic deficiency in roof and floors:

Earthquake resilient features in roof and floors:

Seismic deficiency in foundation:

Earthquake-resilient features in foundation:

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

Additional comments section 5: General lack of awareness about the earthquake resistant construction practices.

Additional comments on seismic strengthening provisions:

Has seismic strengthening described in the above table been performed? Proposed for the damaged buildings of 2003 Rangamati earthquake.

Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? N/A

Was the construction inspected in the same manner as new construction? N/A

Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? N/A

What has been the performance of retrofitted buildings of this type in subsequent earthquakes? N/A

Additional comments section 6:

• Report on “Seismic Risk of Five Selected Cities of Bangladesh” for CARE-Bangladesh, BUET. February, 2003. Project Leader Dr. Mehedi A. Ansary

• Bangladesh National Building Code, 1993

• Guidelines for Earthquake Resistant Non-engineered Construction IAEE