Repairs to Plaster

• The masonry joints which become exposed after removal of old plaster are raked out to a minimum depth of 10 mm in the case of brickwork and 20 mm in case of stonework.
• The loose mortar is dusted off and the surface thoroughly washed with water and kept wet till plastering is commenced.
• Concrete surfaces are thoroughly scrubbed with wire brushes after the plaster had been cut out and pock marked; surface cleaned and thoroughly washed and kept wet till plastering is started.

Repairs to Damaged RCC Columns and Beams

• The structure which as cracked, or where reinforcement has deteriorated can be repaired by guniting.
• Any existing plaster on RCC work is removed and surface roughened with foot marks at least 6 mm deep at close intervals not more than 1 cm centre to form a band for the cement gunite plaster.
• All cracks are opened out to maximum depth possible in V shape and surface cleaned of all loose mortar and foreign matter.
• Reinforcement bars are cleaned to remove all scales and rust by wire brushing and by rubbing with emery paper.
• A coat of neat cement slurry is applied on the existing reinforcement after cleaning it just before the guniting is done.
• Guniting is a mixture of cement and sand deposited in the form of cement plaster ranging from 12 mm to 50 mm thick for a walls and 100 mm for floors, ejected under a pressure of 2 to 3 kg/sq.cm. from a ‘cement gun’.
• The cement and sand are mixed almost dry through a hose and water just sufficient for the purpose of hydration added at the nozzle.
• A separate hose carries the water to the nozzle under a pressure of 1 to 1.5 kg/sq.cm., and the nozzle man regulates the quantity by means of a hand operated valve.

 

Repairs to Leakage in Lavatory Rooms

• Where roof slab of lavatory is found to be leaky, it may be that joints between soil pipes and the accessories are not done properly due to which waste water leaks through the joints.
• But in many other cases, it is found that the joints are all properly laid and yet the waste water leaks through the roof.
• On minute observation, it is found that the porcelain P or S traps are cracked, through which the waste water leaks through the roof.
• The reason for the porcelain trap to get cracked, is that when the waste matter does not pass through the soil pipe properly and the waste gets accumulated in the water closet, the cleaner tries to clean the trap with a wooden stick or an iron rod and during the process the trap gets cracked.
• The cracked traps should be replaced with new ones.

Repairs to Damaged RCC Roof Slab

• Where concrete with plaster below reinforcement of RCC roof has fallen down and the exposed reinforcement has become rusty – this may be due to leaky roof, where water has entered concrete and rusted the reinforcement.
• Or, it may be because of salty water of sand used in the concrete.
• Whatever may be the reason, the best remedy is to provide either wooden or precast RCC battens at 45 cm centers supporting the roof with 23 cm bearing on wall. (The size of battens should be calculated to take the roof and slab loads)
• the roof slab in-between rafter shall be plastered with 1:3 cement mortar 5 cm thick.
• This will ensure a long life to the roof slab.
• To prevent further leakage of water, a new weather proofing course shall be laid on the roof slab.
• Cracks in the slab should be grouted with cement mortar.

Removal of Walls in Existing Building to Increase the Size of Room

• Keeping the existing roof as it is, if the load bearing wall is to be removed, then it is necessary to find out the weight of the roof coming on the wall and also the weight of the wall if any on the next floor.
• After calculating the weight, the size of the steel girder that could support the weight is decided.
• It is necessary to verify if the side walls on which the girder would be resting will be able to carry the load from the girder.
• In case of doubt, it is necessary to remove at least 45cm width of existing wall at the point of support and erect new brick pillar in cement mortar for a width of 45cm and thickness equivalent to the thickness of the wall or 35cm whichever is greater.
• Before removing the wall, the roof should be supported with runners and wooden posts.
• It is always safer to provide two steel girders of equal size in the place of the wall so that for placing one girder only half the thickness of wall abutting the roof need to be broken and the girder placed in position.
• The next day, the other half thickness of the wall is broken and the second girder is placed in position.
• This method of working ensures safety to the building.