General
guidance regarding the seismic safety of masonry buildings
* A single storey
building using one brick walls will be relatively safer than three storey
one. The fourth storey, if added, will be unsafe, and make the tower stories
more vulnerable.

  • Use of half-brick
    thick (10 to 11.5 cm or 4 to 4.5� thickness) load bearing walls will make the
    storey very unsafe during seismic intensity VIII on MSK intensity scale and
    if used in 3rd or 4th storey, it may have catastrophic failure.
  • Too many window
    openings make a wall weaker, and use of smaller size piers less than 18
    inches (45cm) in width between them will increase the damageability even
    higher.
  • Richer
    cement-sand mortar of 1:4 mixtures (1part cement by 4 parts of sand) makes
    the masonry stronger against earthquake shaking as compared with 1:6 mortars
    by factor of 2.5 to 3. Also 1:6 mortars are stronger than lime-cinder or
    lime-surkhi mortar.
  • Use of clay mud
    mortar produces the weakest masonry. Its strength in dry condition reduces to
    less than 50% when the walls get wet during rains. Hence, use of good
    plastering is essential to protect such masonry during rainy months.
  • Longer walls
    between consecutive cross walls are found weaker than shorter walls. The
    length is controlled by limiting its height to thickness ratio.
  • Taller walls
    between any two floors are found to be weaker than shorter walls. The storey
    height is controlled by limiting its height to thickness ratio.
  • All four walls
    enclosing a room should be properly connected at each corner. Walls not so
    connected will easily separate at corners and overturn under the earthquake
    motion.
  • The most
    important seismic safety requirement is provision of seismic bands in all
    stories in all external as well as internal walls. These bands maintain the
    integrity of the whole building as one unit under earthquake shaking. Besides
    the earthquake safety, they also increase the stability of the walls under
    the vertical loads.
  • The roof
    structure of the sloping roofs needs its integrity through bracing and proper
    connectivity with the walls. Such integrity is automatically provided by
    reinforced concrete slabs wherever used for floors and the roof.