Prepared By Alka Shah Civil Engineering Why Damp

Prepared By: Alka Shah Civil Engineering

Why Damp Proofing is required?

Defects caused by Dampness • Causes efflorescence which may ultimately result in disintegration of bricks, stones, tiles etc. • Result in softening & crumbling of plaster • Results in bleaching & flaking of paint with formation of colored patches • Results in warping, buckling & rotting of timber • Corrosion of metals • Deterioration of electrical fittings • Promote the growth of termites • Breeds mosquitoes & creates unhealthy living conditions

Damp proofing and Water proofing (IS: 4911) • Building should be dry or free from moisture in the walls • Dampness is presence of moisture • Treatment to roof: Water proofing • Treatment to floor & basement: Damp proofing

Causes of Dampness • • • Absorption of moisture by building materials Faulty design, bad workmanship or use of defective materials Crack or inhomogeneous joints at foundation, plinth, walls, Chajja, floors or roof. Leakages in wet areas of building like kitchen, bathroom etc. Inadequate slope at flat roof/terrace or improper rainwater pipe connection and defective junction between roof slab & parapet • Penetration of rain water through unprotected tops of walls, parapets, compound walls etc. • Condensation of atmospheric moisture and its deposition on walls, ceiling & floors

Outside damaged pointing and damaged interior

Leakage from Ceiling Damaged interiors

DPC (IS: 3067) • Brick masonry below GL absorb moisture from adjacent ground • Moisture travels up by capillary action and can make the wall damp for considerable height • To prevent this, a continuous layer of an impervious material is provided, known as the Damp Proof course • All building must be provided with DPC at plinth level • Composition of DPC: 50 mm thick cement concrete 1: 2: 4 with water proofing compound(IS: 2645) • DPC must be extended for full width of wall and continuous for entire length of the building, no joints • DPC does not carried across doorways, verandah, arches and similar openings

DPC (IS: 3067) By Hot Bitumen • Application of bitumen: dried up surface of the cement concrete DPC is properly cleaned with brushes and finally with piece of cloth soaked in kerosene oil before application of hot bitumen. • Bitumen of penetration 80/100 should be heated to 160°. • Hot bitumen is applied in two coats at rate of 1. 7 kg/cm 2.

DPC of Floors By Bitumen Felt • Areas having High water tables: • Provide DPC of flexible material like bitumen felt (Hessian based or Glass fibre based) or Plastic sheets over entire area of ground floor.

DPC membrane at different levels

DPC of Floors By Coarse sand • Dry areas having Low water tables: • 75 mm thick layer of coarse sand is generally spread over on prepared bed of rammed earth. • Rise of capillary water in granular soils is almost negligible. • 75 -100 mm thick layer of lean concrete (1: 3: 6 or 1: 4: 8 mix).

DPC for UG tank or in the basement

To control dampness following are Treatments to External walls: • Walls get damp due to porosity of bricks and mortar joints • Treatment like plastering, pointing etc. help to prevent dampness • Non water proof cladding such as stone tiles with open joints should not be constructed so that they do not form pool of water against external wall • Projections like Chajja, balconies and porches should be constructed so that they do not form pool of water against external wall • Painting surface with waterproof cement paint or acrylic paint

DPC Material DPC container with nozzle

DPC Material

Reduce Dampness by Water proofing of Flat Roofs: • Mud phuska terracing & paving with brick tiles(IS: 2115) • Lime concrete terracing & paving with brick tiles(IS: 3036) • Four course or six course waterproofing treatment using self finished bitumen tar felt(IS: 1609) • Polymer modified bitumen polyester membrane water proofing treatment(as above) • Application of bitumen mastic for water proofing of roofs. Recommended for colder areas(IS: 4365)

Slope in the roof : • For efficient drainage should not be less than 1 in 60 • Size of rain water pipe(IS: 2527): 100 mm dia pipe for every 40 m 2 area of roof • Thermal Insulation: Provided above the terrace to save the slab from excessive dimensional change. • Material : Expanded polystyrene, polyurethane foam, foam concrete etc.

Water Proofing by Pressure Grouting • Forcing of cement grout , under pressure in to cracks, voids, fissures etc. present in the parts of building • Structure is made water-penetration-resistant to check seepage of raised ground water through foundation and substructure of a building

Pressure Grouting

Water Proofing By Gunning • Deposition of rich cement mortar under pressure over exposed surface for water proofing or over pipes, cisterns etc. for resisting water pressure • Cement mortar of 1: 3 shot by cement gun under pressure of 2 -3 kg/cm 2 from the distance of 75 -90 cm • Desired thickness and consistency of mortar is deposited • Cured for 10 days