Cracks must be repaired immediately when observed otherwise the life of structure will reduce causing structural failure. They not only weaken the building but spoil the beauty of walls also. This write up tells you about repair of cracks in plaster, RCC member, Brick walls, Floor and Fine Cracks.
The cracks can be prevented at the time of construction. To know more about prevention of cracks during construction, click at the link below.
Two types of cracks are found on surface of plaster i.e. A. Crack with hollow sound in plaster. B. Crack with no hollow sound in plaster. Hollow sound can be checked by striking the plaster.
A. Repair cracks giving hollow sound
Remove plaster applying proper cut
Defective plaster should be removed and the edges should be slightly cut in square or rectangular shape to provide a neat joint.
Prepare the surface thoroughly
Clean the surface with wire brushes and wash it. Wet the surface 24 hours before application of cement mortar.
Apply fresh cement mortar and finish the surface
Defective portion should be filled in with cement mortar. Keep the surface wet at least for 3 days. When surface is dry, finish it according to adjoining area on the wall.
B. Repair cracks if it is solid without hollow sound
Clean cracked portion of all loose materials and fill crack seal sealants in cracked portion. Finally finish the surface according to adjoining area.
NOTE: Plastering is done after cleaning. To know the process of ‘Plastering’ click on the link
Repair Cracks on RCC Surface
Clean cracked portion and apply guniting
The cracked portion should be widen gently and be cleaned of all loose materials. Fill the cracked portion by pressure grouting or ‘guniting’. The material for such grouting can be epoxy or cement (with suitable admixture).
Apply epoxy and finish the surface
Epoxy has more strength and adhesion than cement and can go into very thin cracks as fine as 0.1 mm. The surface should be finished according to adjacent area on the wall.
Note: The cracks in RCC members/ structural members should be repaired immediately with consultation form structural engineer/professional.
Repair Cracks on face of plaster
When two components having different elastic properties such as RCC slab and brick work abating each other, the crack on face of plaster is formed between these components due to their thermal expansion.
Remove plaster and old material
The plaster should be removed from cracked portion. The joints should be widened at least 20 mm to 25 mm in thickness. Clean old material by washing and brushing.
Apply cut and prepare the surface
Apply slight cut on edges in straight line to provide neat joint. Make the surface damp 24 hours before application of new plaster.
Apply cement mortar
Cement mortar should be applied on defective portion. Make 20 mm wide and 25 mm thick groove at the junction of two materials/components.
Do curing and finishing
Keep the surface wet at least for 3 days. When surface is dry, finish it according to adjacent area on wall.
Repair Cracks in Masonry Walls
Two types of cracks are seen in masonry walls i.e. A. Crack in mortar joints of walls. B. Crack in bricks/Diagonal Cracks
A. Repair cracks in mortar joints of walls
The mortar should be removed from cracked joint with the help of iron tools at least up to 25 mm depth. All loose material should be cleaned from cracked portion.
Wet the surface and apply cement mortar
Cracked portion must be kept moist at least for 24 hours before doing repair. Fill in the joints with cement mortar of coarse sand in 1:4.
Do curing and finishing
After filling the joints with cement mortar, keep the repaired surface wet at least for 3 days. After drying the surface, finish the repaired area according to the adjoining area.
B. Repair cracks in bricks/diagonal cracks
Remove broken bricks
Before doing any repair of cracks, make sure that the cracks are stabilized and are not widening further. Remove broken bricks by scratching cement mortar from the joints gently.
Prepare the surface
All loose material should be cleaned from the portion by brushing and washing. Wet the surface 24 hours before application of new plaster.
Fix new bricks thoroughly
Lay fresh cement mortar with coarse sand in 1:4 and fix new bricks. Fill all joints around bricks with mortar tightly with the help of iron tools.
Do curing and finishing
The repaired surface should be kept moist up to 7 days. When surface is dry, it should be finished according to adjoining area.
Remove loose material and apply mortar
Create V shape groove in cracked portion and remove all loose material by washing and brushing. Fill in the groove with polymer modified mortar (for wide cracks) or with polymer modified cement grout (for thin cracks).
Remove cracked panel or material
If there are many cracks in the floor, remove cracked panels and old materials.
Prepare the surface and lay new panel
Clean the panel by washing and brushing. Prepare floor material according to the existing floor and lay new panel.
Note: To know more on ‘How to Lay Floor’ in detail, you can click at the link given below on our website.
Repair Hair Cracks in plaster
Broaden the crack gently
Widen the crack about ¼ inches with chisel and remove all loose plaster from the cracked portion.
Apply vinyl spackle compound
Use vinyl spackle compound to fill the cracked portion. Press the vinyl spackle into the crack and let it dry. Sand or sponge the surface smooth.
Seal the patch and finish the surface
Seal the patch with proper priming coat and finish it with proper shade according to the adjoining area.
Repair Fine cracks
- Apply surface water proof coating on the entire area having very fine cracks (especially on roof) where filling /sealing of each individual crack is not possible.
- Do proper curing of repaired area at least for 3 days.