Buildings are loaded with different
types of loads (Live Loads, Dead Loads, Seismic Loads) which develops stresses
in different parts of building and when these stresses exceeds allowable limits
then causes cracks.
There are several methods to avoid
cracks in buildings.
1- Design and Construction of
Foundations.
Design and construction of foundations is the most important part which
can cause cracks in building structure. First of all do soil investigation and
find bearing capacity of soil at different depth and layers beneath Ground
Level. Adopt bearing capacity at
suitable depth avoiding subsurface water level because water level fluctuation
causes extra stresses into foundations.
If sub-surface water level is close
to the ground level then provide a Mix of Riverbed Stone and course-sand using
equal ratio of by parts and with proper compaction, then provide Plain cement
concrete which will provide stiffness while transferring the loads to sub-grade
avoiding deformation in sub-grade which can cause uplift of water.
After providing plain cement
concrete provide foundation structure which may be brick stepping of Reinforced
Cement concrete whatever is feasible ,If adopting brick stepping in foundation
than must provide plinth beam with 9 inch width and minimum depth of 6 inches.
Size of Plinth beam may be raised according to height and weight of building.
To design the size of beam Bending moment may be calculated using 3ft to 5ft as
effective span of beam and apply proper loading by area division and wall loads
on beams/ foundation.
Remember Do not try to compact excavated ground level where moisture exceeds
15 % because extra moisture never helps to get required dry density during
compaction. At such conditions provide Riverbed Stones and sand mix or provide
brick soling under the foundations.
Calculate width of footing comparing
to factored loads bearing capacity of soil.
2-In water logged areas provide
Columns having basis merged striped RCC (1:2:4) OR RCC (1:1.5:3) footings at
Wall corners and mid of walls (If span of rooms exceeds from 18 Ft) jointed
with plinth beams (With same width as of columns). Brace all columns at Door/Window
Lintel levels and finally brace at roof slab levels.
3- In water logged areas
under-ground sub-surface drains may be constructed around the building to keep
water level at reasonable distance from foundation of buildings.
4-Wall grooving for piping of water
supply ,Gas, Electric Pipes or sewer pipes may also cause the cracking in walls
so special care is needed and during fixing of pipes fill the cavities with
proper cement concretes then plaster the surface after placing of chicken mesh.
5-Minimum load bearing wall
thickness should be 9" inches so do not use smaller walls as load bearing
walls as this can also the causes of cracks.
6-Provide Shear Walls in building to
minimize lateral stresses caused by lateral loads which can also the main cause
of cracks in buildings.
The areas where intensities of
earthquakes are higher diagonal beams connecting bottom and tops of columns may
be provided to minimize shear loads on walls caused by lateral loads during
earthquakes.
7- If load bearing walls are brick
walls then do calculation checks to avoid exceed of loadings. Brickwork
allowable loading is 50 % of brick bearable loads. So design the walls keeping
this check. Construct the walls with properly mixed mortars filling all joints
of bricks as per thickness of mortars using brick courses distribution and leveling.
8-Place building paper between slab
and wall top to avoid extra stresses caused by contraction and expansion
movements of slabs.
9-Adopt proper method for doing of
concrete works of RCC and PCC because the main loading material in building
works is concrete.
10- Provide RCC concrete pads under
the beams if beams are directly resting at load bearing brick or block walls as
this may also the cause of crack due to shear load of beam.
11- Fill and compact good class of
filling sandy materials under the floors because during settlement floors
exerts horizontal pressures on walls which can cause cracks.
11- Do not place electric pipes in
concrete covers of RCC Slabs as in most of building hair cracks have been seen
on the routes of electric pipes.
12-Walls and Columns should be
constructed vertically because it may produce extra stresses in brick work and
RCC concretes and also requires extra thick plaster which cracks due to
extra self load of plastering.
13- Provide expansion and
contraction joints and reasonable interval and according to produced stresses
due to the self load of building parts.
14-Adopt working methodology to
avoid any moisture leakage in building structure because of water supply lines
,rain water, and sewer lines.
Building should be fully water tight
as it may also be the cause of weaken and cracking the building parts.
15-Design all parts properly and
keep good factor of safety for RCC structures and vertical members. Factor of
safety may 3 for all parts of buildings.
16- Construction team should be well
experienced and professional to execute and supervise the works according to
engineering standards.
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