How to Avoid Cracks in Buildings

 

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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