Adopting the sophisticated building regulations of the developed world in poor countries has
done little to prevent poor people's housing from collapsing in earthquakes. There are many
ways of making stone and adobe buildings better able to resist earthquakes which are within
the reach of people on low incomes.
Earthquakes cause a lot of
casualties and damage. In the
twentieth century alone, they
have accounted for around 1.5
million casualties, 90 per cent
of which occurred in housing
for people with a low income.
The economic losses have been
staggering as well: they may
have exceeded one trillion US
The particular vulnerability of
poor people's housing is caused
by a number of factors, of
which the most important are:
Figure 1 - Typical domestic tapial dwelling destroyed by
earthquake (Megan Lloyd-Laney)
Poverty, which prevents
the use of better
materials or skills. It
also makes people
extend and improve
their houses in stages,
and in the case of a
house that has got off
to a bad start it is often
hard to improve its
A lack of political
power, which stops
people building on
Figure 2 – Earthquake resistant quincha house (Theo
more secure sites or
Scarcity of both
appropriate materials and skills for earthquake-resistant construction.
A lack of disaster consciousness in situations where daily survival is a major problem,
and where, for example, the removal of subsidies on food is a much greater disaster for
poor people than the eventual earthquake.
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Earthquake protection for poor people’s houses
Any effort that helps to reduce the vulnerability of poor people to disasters, and thereby also
reduce casualties and future economic losses, is worthwhile in itself. As in the area of medicine,
where money spent on the prevention of a disease reduces the amount required for its cure, so
aid agencies as well as local governments should spend larger parts of their disaster budgets on
reducing vulnerability instead of on relief. If one looks at the factors listed earlier, it becomes
clear that only long-term development work will considerably reduce vulnerability: if poor people
gain more resources and more power they will become less vulnerable. And it often does not
need large sums to get this process going, as Andrew Maskrey describes in his excellent book
Disaster Mitigation – a community based approach.
Better technologies are needed to reduce the vulnerability to earthquakes of the housing of lowincome groups, but we cannot impose such technologies upon people. The approach that most
developing countries have attempted is simply to adopt a set of standards and regulations with
respect to the earthquake resistance of buildings which are directly derived from the ones used
in the USA, Britain or France. They usually prescribe reinforced-concrete frames or some other
technology that is unaffordable by the poor, and like other standards, they have been ignored by
the poor. Engineers should learn not to aim for the ideal solution, but for the affordable and
appropriate solution; they have to allow a higher level of risk than standards usually permit, and
they may have to set priorities.
An example of such a priority might be the prevention of casualties as a result of roof collapse,
and some engineers have actually designed separate roof-supporting systems, accepting that if
masonry walls fall down, they can be rebuilt afterwards.
The best approach to increasing earthquake resistance is usually to learn from the earthquake
performance of dwellings in a given area, noticing problem areas and sometimes better
technologies, and then to use mainly local resources for further improvement. The rest of this
article gives some examples of improvements to three types of construction: stone masonry,
adobe masonry and quincha.
Earthquakes make buildings shake; the resulting lateral forces are determined by the mass of the
building. Dwellings with heavy walls and roofs therefore run the greatest risks, and these are very
common in the major earthquake belts that encircle our globe, such as Central and South
America, the Mediterranean, the Near East and China.
Heavy walls may be damaged as a result of:
shear stress, caused by forces parallel to the plane of the wall, and resulting in diagonal
cracks developing in high-stress areas, such as corners, intersections or openings;
forces perpendicular to the wall, causing bending out of plane;
a combination of these two stresses.
Random stone masonry, which occurs widely in the Mediterranean and the Near East, is very
dangerous in earthquakes. These walls lack internal cohesion and even disintegrate during
moderate earthquakes; this has happened during earthquakes in Lice, Turkey; in Yemen; in
Pakistan; and in Iran.
Adobe, or soil-block masonry, is even more common in poor people's housing. The cohesion and
the tensile strength of adobe walls are often insufficient to resist even a moderate earthquake:
walls shear apart in high-stress areas; they incline and are pushed outwards by the roof, which
then may fall on the inhabitants. Adobe structures have contributed most to the number of
earthquake casualties, particularly in Latin America, the Near East and China. Bad performance
has often been caused by such factors as poor adobe quality, poor bonding and poor
workmanship, a lack of maintenance and the presence of humidity in the walls.
Earthquake protection for poor people’s houses
Mud and pole construction is a method that occurs independently in many developing countries.
It consists of a round pole frame which was set directly into the ground, infilled with smaller
wooden poles and interwoven to form a matrix which is then plastered with one or more layers of
earth. Timber buildings in a seismic area usually fare better in an earthquake due to the
flexibility of the material and the buildings and their light weight compared to concrete or steel.
Weaknesses in this type of construction lie in the weakening of the timber poles due to rot,
insect and fungal attack, and often in poor connections in the timber frame. Deterioration of the
frame can be avoided by preventing exposure of the timber poles to moisture by using
preservative treatment and preventing contact with the soil moisture at foundation level.
In Peru, this type of construction is known as quincha. Many heritage earthen buildings higher
than one storey usually have a lighter second storey constructed in quincha in response to the
1746 earthquake in Lima. Some newly constructed adobe buildings designed to be seismically
resistant have also included a second storey made of quincha. It significantly reduces the mass
of the second storey and attracts less seismic forces on the building.
Some design guidelines
The study of the performance of buildings during earthquakes tells us something about the
relative resistance of various building technologies. Even with the same technologies, however,
we often notice variations, caused by other factors, such as the design or location. Improvements
to the technologies would be less effective if these factors were not taken into account. Some
major guidelines are:
Carry out a site investigation;
Select a solid site; avoid landfills, flood plains, drainage paths and steep slopes;
Position the foundations on rock or firm soil, avoid stepped foundations;
Design compact buildings with a symmetrical shape and closely spaced walls in both
directions. If that cannot be done, design them in separate, regular blocks;
Build one-storey houses where possible;
If buildings have more than one floor, opt for similar floor shapes and designs;
Separate adjacent small buildings by at least 75 mm;
Make walls light to reduce the horizontal forces caused by earthquakes;
Walls should not exceed 3.5m in height, unsupported lengths of wall should not exceed
Make roofs light to avoid them pushing walls sideways and falling-in on people;
Avoid gables, they may fall inwards;
Avoid long walls without intermediate support and tie walls together at the top
Keep openings to a minimum, well distributed over the building and within walls; keep
them centrally positioned, at least 60 cm away from the inside of corners and
intersections and from the nearest other opening.
Openings should not be wider than 1.2m and bearings of lintels should be at least
500mm either side of the opening;
Provide strong joints between structural components; use a ring beam and a plinth beam
where possible; use bracing at corners;
If masonry walls are used, create good bond especially at corners and intersections;
If concrete pillars are used, lap vertical reinforcements mid way between floors and not
just above floors;
Control the quality of the materials used.
Improve the workmanship, particularly in mortar preparation, masonry and connections.
For an illustrated guide of the above points and more useful advice on good practice, the
Earthquake Reconstruction and Rehabilitation Authority in Pakistan have published a guidelines
Earthquake protection for poor people’s houses
Improving stone masonry
In the Near East, the reinforcement of masonry has much improved the performance of stone.
The materials used for reinforcement are concrete or timber, the latter being far cheaper.
Horizontal tie-beams are essential, and they can be combined with a vertical frame, and, in the
case of timber, diagonal bracing.
Horizontal tie-beams should appear at roof level, above windows and doors, and sometimes also
below windows and on top of the foundations. Full frames are an expensive way of reinforcing a
building. It is more affordable, but also more risky, to reinforce only the high-stress areas – near
openings, corners or intersections – with shorter pieces of timber or steel.
A better quality of materials also increases resistance. Round stones should be avoided; angular
stones, preferably dressed, will considerably improve the internal bond in a wall. The use of
flatter stones, such as slate, will help as well, as long as they are placed flat, not on their side.
Better mortars increase the bonding, which is particularly important for corners and intersections
and around openings. Wherever available and affordable, the use of cement, lime pozzolana,
lime or gypsum mortar (in that order of preference) should be encouraged. (A pozzolana is a
substance which, when mixed with lime and water, hardens as a cement.)
A high level of construction quality is important, particularly to improve bonding and therefore
resistance to movement. The practice of building double- faced walls, without tie stones and
with rubble infill should be strictly avoided. Stones should always be placed as flat as possible,
and dressed whenever needed to fit specific gaps, rather than using large quantities of mortar
and small stones to fill up voids. Vertical joints should be staggered so that large vertical cracks
do not occur. Masonry walls should occasionally have stones that reach through the entire
thickness of the wall ('through-stones',) which perform the same tying functions as the dowels
(steel or wooden connecting pieces). Finally, walls should be neither too thin, which makes good
masonry patterns very hard to realize, nor too thick, since that would unnecessarily increase the
mass. A reasonable thickness for masonry with irregularly shaped stones is in the order of 40 to
For adobe reinforcement often provides the biggest improvement to the masonry. A continuous
ring-beam is very desirable, particularly at roof level; it helps to tie the tops of the walls together
and provides a fixed base for the roof. Continuity can be ensured by lapping the reinforcement or
splicing the timber. If there are many openings, or if walls are greater than 2.5m in height, a
similar ring-beam at lintel level is recommended. If unable to resist great lateral forces
themselves, walls may still move sideways during earthquakes, unless vertical reinforcement is
added to tie them to the foundations and to increase bending resistance. Vertical reinforcement
is particularly useful in high-stress areas: at corners or intersections of walls and along openings.
A picture of an ideal combination of reinforcement is shown in Figure 2.
Earthquake protection for poor people’s houses
Reinforcement for ring beams may take many shapes:
Concrete columns and beams are the most expensive solution.
Timber beams, on top of and within the walls are usually much cheaper. The Turkish
building code suggests the use of horizontal timber bond-beams at four levels: at the
basement, under and above windows, and under the roof. These bond-beams can be
double, with a 10 x 10cm timber profile at
each side of the wall, connected by 5 x 10cm
ties at 50cm intervals (Figure 3). They can
also be single, on the outer face of the wall,
and braced in the corners (Figure 4).
Timber frames were also suggested after the
1976 earthquake in Guatemala, where the
traditional adobe wall is much thinner,
provides little structural support, and acts as
more of an infill than elsewhere. The frame
should consist of horizontal beams at roof and
basement levels with vertical posts at corners Figure 5
and intersections, and braces to make the
frame more rigid (Figure 5). Such wooden
frames require good connections with the
adobe masonry, through anchor bolts, nails or
In Mexico, U-shaped or hollow adobes have
been suggested, to incorporate timber or
concrete reinforcement more easily (Figure 6).
Steel bars can be used, in horizontal or
vertical joints, to tie walls together or to the
foundation, but they are expensive. In Ecuador
and Honduras barbed wire or other steel wire
has therefore been suggested for use in
combination with a timber frame (Figure 7).
Welded mesh in the joints is an alternative
commonly used in the south west of the USA
and in southern Africa (Figure 8). Wire mesh
incorporated into a plaster becomes
ferrocement, and can be used to reinforce
high-stress areas, around corners or openings
The Turkish code allows the wooden bondbeams to be replaced by canes 5cm apart,
tied every 50cm. In Peru, both vertical and
horizontal reinforcements with reeds and
bamboo are used. One method uses bitumenstabilized adobes (bitumen is mixed in with the soil), with small holes in the vertical
joints for a halved bamboo (also painted with bitumen) to pass through. Horizontal
reinforcement then consists of quartered bamboo laths (Figure 10).
In India, split bamboo mesh, dipped in bitumen, is used as a reinforcement of the
plaster on adobe walls.