Methods Of Damp Proofing In Building

What Is Damp Proofing?

Damp-proofing is a method of preventing the entry of water or moisture into the structure. It is done by providing an impermeable layer between the source of dampness and part of the building. 

The efficient impermeable layer must be durable, resist loads, and accommodate structural movements without fractures.

There are many methods, but below we have discussed six important damp proofing methods which are widely practiced and have a great outcome.

Methods of Damp Proofing

The following methods are generally practiced to prevent dampness in a structure.

1. Membrane Damp-proofing,
2. Guniting,
3. Surface Treatment,
4. Integral Damp-proofing,
5. Cavity Wall Construction,
6. Pressure Grouting or Cementation.

1. Membrane Damp Proofing

Membrane damp-proofing consists of a layer or membrane with a water-barrier material between the dampness source and the part of the structure that needs to be protected.

Membrane damp-proofing is commonly known as a damp proof course (or D.P.C.), and materials such as mastic asphalt, bituminous felt, polymers, plastics, silicone, epoxy, cement concrete, etc. are used in this method of damp proofing.

Based on the source of dampness, the Membrane damp-proofing method can be applied horizontally or vertically on floors, walls, etc.

2. Guniting

Guniting is a Damp Proofing technique in which a rich mortar mix of 1:3 is applied or shot on the exposed surface under very high pneumatic pressure using a cement gun”. Guniting is also known as shot concrete.

In the guniting method, a waterproof layer of rich mortar is spread or shot over an exposed surface to make it water-resistant. The exposed surfaces can be any part of the structure, such as inferior concrete, masonry walls, pipes, cisterns, etc. 

The applied mortar becomes very hard, strong, and water-repellent on that surface. This method of damp proofing is very useful during structure retrofitting and repairing old concrete works or monument structures.

3. Surface Treatment

Surface treatment is a method of applying a layer of water resistance substances or compounds on the surface to be protected to restrict moisture from entering the structure. 

Many exposed surfaces of the structure are given surface treatments such as pointing, plaster, and painting. While the most common surface treatment given to walls is lime cement plaster (1 cement: 6 Lime).

This treatment is done by mixing plaster coating with any waterproofing admixtures like aluminum hydroxide, sodium, or potassium silicates.

The exposed surfaces of the structure must be Painted and plastered carefully, using water-repellent agents like aluminum or zinc sulfates, sodium or potassium silicates, magnesium sulfate, and barium hydroxide, etc. 

The surface treatment method is subjected to achieve better results only when the mixture is superficial and not under pressure. Sometimes water repellent solutions are sprayed on exposed stone and brick surface walls.

4. Integral Damp Proofing

In the integral damp proofing method, the waterproofing compounds are mixed into the concrete or metal of the structure to make the surface impermeable.

Compounds like talc, fly ash, Chalk, etc., fill the pores in the concrete or mortar and make it hard and less porous. Some waterproof compounds like sulfate and calcium chloride chemically react with concrete and fill the pores to make them water-repellent.

While Some compounds work on repulsion principles like oils, fatty acids, soaps, and petroleum compounds such as stearates of calcium, when these compounds are used as an admixture in concrete, they react with it and make it water-resistant.

5. Cavity Wall Construction 

Cavity wall construction is one of the damp-proofing methods in which a cavity or gap or space is formed between the main wall and cavity wall, which helps resist the entry of water or moisture into the main wall, thus making the structure waterproof.

Due to minimal or zero contact between the outer and inner walls of the cavity wall, there is less chance of moisture penetration, and the transmission of heat through the wall is prevented cavity wall.

There are other advantages of a cavity wall, such as it can act as good insulation against sound and reduce the nuisance of efflorescence. Cavity wall construction is economical and provides hygienic conditions in the buildings.

6. Pressure Grouting Or Cementation

In this damp proofing method, the mixture of cement mortar (cement, sand, water) of fluid consistency is used to fill the voids and cracks or fissures present in the structure known as Grouting. 

This grout mixture differs from conventional mortar in terms of fluidity as it is filled in cracks not to be spread like mortar. In the case of wide cracks, grout is poured at high pressure to fill the crack. 

This method of damp proofing is widely used in foundations to repair, harden and set concrete, and consolidate ground to improve bearing capacity; this helps to prevent water entry into the structure.

Also Read

Dampness In Buildings – Causes & Prevention

Cavity Wall – Advantages & Construction Process

Types Of Waterproofing Membranes For Buildings

How To Select Materials For Damp Proof Course (DPC)

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