Damp proof course

1,554 views 17 slides Jun 03, 2019
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About This Presentation

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Slide Content

DAMP PROOF COURSE PRESENTED BY AGLAIA

What is DPC? Damp proof course is used to restricts the movement of moisture through walls and floors. There are mainly methods of damp proofing Membrane damp proofing Gunting Integral damp proofing Surface treatment Cavity wall construction Pressure grouting

Causes of dampness Rising of moisture from the ground. Rain travel from wall tops. Poor drainage, imperfect orientation, imperfect roof slope, defective construction etc. bricks suck dampness from soil underneath and pump it to building due to capillary force.

Harmful Effects of dampness dampness reduces the strength of the structure. Dampness cause falling down of plaster results in unpleasant appearance. It causes insect and germ growth.

Properties of Materials for DPC It should be impervious. It should be strong and durable, and should be capable of withstanding both dead as well as live loads without damage. It should be dimensionally stable. It should be free from deliquescent salts like sulphates , chlorides and nitrates.

Types of Materials for Damp Proof Course Flexible Materials : Materials like bitumen felts (which may be hessian based or fiber/glass fiber based), plastic sheeting (polythene sheets) etc. Semi-rigid Materials : Materials like mastic, asphalt, or combination of materials or layers. Rigid Materials : Materials like first class bricks, stones, slate, cement concrete etc.

Methods of damp proofing Membrane damp proofing Integral damp proofing Guinting Surface treatment Cavity wall construction Pressure grouting.

1. Membrane damp proofing A water  repellent membrane or damp proof course is introduced in between the source of dampness and the part of building adjacent to it . DPC may consist of flexible materials such as bitumen, mastic asphalt, bituminous felts, plastic or polythene sheets, metal sheets , cement concrete . It may be provided either horizontally or vertically in floors, walls etc. Provision of DPC in basement is normally termed as ‘Tanking ’.

2. Integral damp proofing In this method certain water proofing compounds are added to the concrete mix, so that it becomes impermeable. The quantity of water proofing compound to be added to cement depends upon the manufacturer’s recommendations. In general 1Kg of water proofing compound is added with one bag of cement to render the mortar or concrete waterproof.

3.Guniting In this an impervious layer of rich cement mortar is deposited under pressure over the exposed surfaces for resisting the water pressure. The operation is carried out by use of a machine known as cement gun. The mortar mix of desired consistency and thickness can be deposited to get an impervious layer. The layer should be properly cured at least for 10 days. Since the material is applied under pressure, it ensures dense compaction and better adhesion of the rich cement mortar and hence the treated surface becomes water proof.

4.Surface treatment In this method a layer of water repellent substances or compounds are applied on these surfaces through which moisture enters. The use of water repellent metallic soaps such as calcium and aluminum oletes and stearates are much effective against rain water penetration.  it is effective only when the moisture is superficial and is not under pressure. Sometimes, exposed stone or brick wall face may be sprayed with water repellent solutions.

Cavity wall construction Cavity wall construction is an effective method of damp prevention. In this method the main wall of a building is shielded by an outer skin wall, leaving a cavity between the two. The cavity prevents the moisture from travelling from the outer to the inner wall.

Pressure grouting It consists of forcing cement grout under pressure, into cracks, voids, fissures and so on present in the structural components of the building, or in the ground. Thus the structural components and the foundations which are liable to moisture penetration are consolidated and are thus made water-penetration-resistant. This method is quite effective in checking the seepage of raised ground water through foundations and sub-structure of a building.

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