DAMP PREVENTION

Moisture prevention is a key requirement for ensuring the protection of the building against moisture.

One of the basic requirements in all buildings is that the structure should be as dry as possible.

If this is not satisfied there is a possibility that the building may be structurally habitable and unsafe.

A course known as moisture proofing course is provided at different levels of moisture penetration in a building to prevent the penetration of moisture into a building.

Presently all buildings are given DPC treatment

Hence DPC prevents the penetration of moisture from the walls, floors and basements of buildings.

The treatment given to the roofs of buildings for some reason is called water proofing.

Cause Of Dampness

The responsible cause is one or more of the following

1. Defective design of the structure

2. Defective construction / poor workmanship

3. Use of substandard material in construction

Due to these reasons there is easy access of moisture to the building from various points, such as rain water through walls, roofs and floors etc. Moisture entering buildings from foundations and roofs travels in different directions under the influence of capillary action and gravity respectively. Water penetration and circulation in different parts of buildings is positively caused by one or more of the reasons listed above

(1) Rise of moisture from the ground

The subsoil or the land on which the building is constructed may be made of soil which provides easy access to water to create moisture in the building. Generally foundation moisture occurs when building structures are constructed in low-water areas where a sub-soil of clay or peat is usually found through which moisture will easily rise under capillary action until not treated properly.

This moisture further finds its way through the plinth to the floor, walls etc.

(2) Action of rain water

Whenever the faces of the walls are not properly protected from exposure due to heavy rain, they become sources of moisture in the structure. Similarly poor mortar joints in walls and broken roofs also allow moisture to permeate the structure of the building. Sometimes due to faulty eave courses and eave gutters, rain water can seep through the roof coverings

(3) Rain Penetration  from the top of the wall

All parapet walls of buildings and walls of premises that have not been protected from rain Penetration are subject to moisture by using dam-proof courses or by such measures at their exposed tops. This dampness in buildings is of a serious nature and can result in unhealthy living conditions or even structurally unsafe conditions.

(4) Codensation due to atmospheric misture

Whenever the warm air in the atmosphere cools, it gives rise to the process of condensation. Condensation causes moisture to accumulate over the entire area of ​​walls, floors and ceilings. However, sources of moisture are prevalent only in a few places in India, where there is a very cold climate.

(5) Miscellaneous sources or reasons

Other various sources responsible for moisture in buildings are mentioned below:-

(a) poor drainage of the site

If the structure is located at a low location, water logging conditions are created when impermeable soil is present under the foundation.

So structures that don't drain well tend to build up moisture in buildings through the foundation.

(b) incomplete orientation

Whenever the direction of the buildings is not right or the geographical conditions are such that the walls of the buildings receive less direct sunlight and more rainfall, such walls become moist.

(c) construction Dampness

If excess water is added during construction or due to poor workmanship, the walls remain in a moist condition for a sufficiently long time.

(d) moisture due to faulty construction

Moisture in buildings is also caused due to poor workmanship or construction methods like insufficient roof slope, faulty rain water pipe connection, proper connection of walls, faulty joints in roofs etc.

Effect Of Dampness (effect of moisture)

The various effects (indirect defects) caused by moisture in buildings are mentioned below:

All the effects result mainly as a result of poor functional performance, ugly appearance and structural weakness of the buildings.

(a) A damp building creates unhealthy living and working conditions for the occupants.

(b) Presence of moist conditions causes efflorescence on the building surface, which may eventually result in disintegration of bricks, stones, tiles etc. and hence loss of strength.

(c) It can cause bleaching and flaking of paint resulting in colored patches on wall surfaces and ceilings.

(d) It may result in corrosion of metals used in the construction of buildings.

(e) Materials used as floor coverings, such as tiles, are damaged as they lose adhesion with the base of the floor.

(f) Wood, when exposed to moist conditions, deteriorates due to the effects of warping, buckling and rolling of the wood.

(g) All electrical fittings are worn out, causing leakage of electric current with potential danger of short circuit.

(h) Moisture encourages the growth of termites and hence creates unhygienic conditions in buildings.

(i) Moisture when combined with heat and darkness, gives rise to germs of tuberculosis, neuralgia, acute and chronic rheumatism etc., resulting in sometimes fatal diseases.

Damp or Moisture protection techniques and methods

The following precautions should be taken to prevent dampness in buildings before applying the various techniques and methods described later:

(I) The site should be located on high ground and well drained soil to protect the foundation from moisture. It should be ensured that the water level is at least 3 metres. The lowest point below the surface of the ground or even in wet weather. The ground surface around the building should also be slope away for better drainage.

(II) All exposed walls should be of sufficient thickness to keep them safe from rain penetration. If the walls are of bricks, their thickness should be at least 30 cm. should be

(III) Bricks of better quality which are free from defects like cracks, defects, lump of limestone should be used. They should absorb water no more than 1/8 of their weight when soaked in water for 24 hours.

(iv) Good quality cement mortar should be used to make a definite pattern and perfect bond in the construction units during the construction work. This is necessary in order to prevent the formation of cavities and the occurrence of differential settlement.

(v) Cornice and string courses should be provided. Window sills, plinths and string courses should be facing upwards to divert rainwater away from the walls and hugged onto the undesirable.

(VI) All exposed surfaces should be covered with waterproofing cement plaster

(VII) Hollow walls are more reliable than solid walls in holding moisture and hence cavity wall construction should be adopted wherever possible.

Prevention of dampness (moisture containment)

(1) The use of damp proofing courses or membranes 

These are layers or membranes of waterproof materials such as bituminous felts, mastic asphalt, plastic sheets, cement concrete, mortars, sheets of metal interlaced at all locations of the building structure wherever water is expected. . These damp proof courses of suitable material should be made available at a suitable place for their effective use. Basically DPC is provided to prevent the rise of water from sub soil to different parts of buildings. The best location for DPC in case of buildings without basement is at plinth level or should be kept at least 15 cm above ground in case of structure without plinth. These damp proof courses can be provided horizontally or vertically in floors, walls etc. In case of DPC laying the basement is known as tanking.

When providing damp-proof courses in buildings, the following general principles should be followed in practice.

• To act as an effective barrier to moisture under all conditions, the DPC must cover the entire thickness of the walls except for the rendering.

• The mortar bed on which the DPC is laid should be flat, even and free from any projections.

• DPC courses should be placed in perfect relation with other DPC courses to provide a complete curriculum so that the passage of moisture from the bottom, top or bottom is complete and provides continuous interruption. Do . Team. Therefore, the junctions and corners formed by walls, or walls and floors, must be kept continuous.

• Where a vertical DPC is to be placed continuous with a horizontal DPC (ie, forming an angled projection), a plaque 75 mm in radius should be provided. The DPC should not be exposed to the wall surface, otherwise it is likely to be damaged by carpentry, tile layers, etc.

(2) waterproof (or damp proof) surface treatment

Surface treatment involves filling the pores of the material exposed to moisture by providing a thin film of water-repellent material on the surface. These surface treatments can be either external or internal, external treatments are effective in retaining moisture, while internal treatments only reduce it to some extent.

Multiple surface treatments such as pointing, plastering. Painting, distempering, exposed surfaces and interior surfaces are also offered. The most commonly used treatment to protect walls from moisture is a plaster (one cement: one lime: six sand) ratio of lime-cement mixture. Water proofing can be a thin film material, commonly employed as a waterproofing agent in surface treatments: sodium or potassium silicate, aluminum or zinc sulfate, barium hydroxide and magnesium sulfate. In alternative applications, there are also alternative applications in soft soaps and lime and linseed oils of alum, bitumen, bitumen, waxes and fats, resins and gums, etc.

Some of the materials mentioned above, such as waxes and fats, are unsuitable in the tropics because they melt with increasing temperature, resins and gums are also not permanent materials, coal tar and bitumen destroy the original surface.

(3) Integral damp-proofing treatment

Integral treatment involves the addition of certain compounds to concrete or mortar during the process of mixing which, when used in construction, act as barriers to moisture penetration under various principles. Compounds such as chalk, talc, fuller's earth, etc. have a mechanical action principle, that is, they fill the pores in the concrete or mortar and make them dense and waterproof. Compounds, such as alkaline, silicate, aluminum sulfate, calcium chloride, etc., work on the principle of chemical action, that is, they react chemically and act as water repellent by filling the pores. Similarly, some compounds like soap, petroleum oil, fatty acid compounds like calcium stearate, sodium ammonium etc. work on the repulsion principle, i.e., are used in concrete to react with it and become water repellent.

Synthetic compounds prepared under this principle are available in commercial forms, such as Pudlo, Sika, Novoid, Ironite, Dampro, Paramo Rainer, etc.

(4) walls of the cavity

★ A cavity wall consists of two parallel walls/leaf/masonry skins, separated by a continuous air space/cavity.

★ It consists of three parts.

• 10 cm thick part of outer wall

• Cavity/Air Space (5cm-8cm)

• Inner wall/leaf (minimum 10 cm thick)

★ The two leaves forming a cavity in the middle may or may not be of equal thickness. The internal wall thickness may be greater to take the larger properties of the loads transmitted by the floor and ceiling.

★ The provision of a continuous cavity in the wall efficiently prevents the transmission of moisture from the outer to the inner wall.

★ Under India's climatic conditions (hot-dry/hot-humid), cavity type construction is most desirable as it offers many advantages such as better living and comfort conditions, economical construction and protection of buildings against moisture.

1. Since there is no contact between the outer and inner walls of the cavity wall except for the walls with impermeable material, the potential for moisture is minimized.

2. It has been verified that a cavity wall of 10 cm thick inner and outer walls is better or more reliable w.r.t. a concrete wall of 20 cm thickness with 5 cm cavity/air space in between.

3. The cavity wall provides good insulation against sound.

4. It reduces the problem of bloating.

5. It provides other benefits like,

• Economy
• Better Comfort
• Sanitary conditions in buildings.

(5) Shot Concrete (Gunting)

It consists in forming an impermeable layer of enriched cement mortar (1:3) on exposed concrete surface to resist water pressure or for water proofing on pipes, cisterns etc. Gunite is a mixture of cement and sand on a well graded fine aggregate, the typical ratio being 1:3 or 1:4. A machine called a cement gun, consisting of a nozzle for spraying the mixture and a drum of compressed air to force the mixture to the desired pressure, any surface to be treated for this purpose, Which is first thoroughly cleaned of any dirt, grease. or loose particles and then completely wet. A mixture of cement and sand is shot at a distance of 75-99 cm from the wall surface under a pressure of 2-3 kg/sq cm by holding the tip of a cement gun. The required quality of water is added through the regulating valve immediately after the mixture comes out from the cement gun. So the mixture of desired consistency and thickness can be sprayed, to obtain an impermeable layer, the impermeable surface should be watered for about 10 days.

High compressive strength impervious layer (28 days strength) can be obtained by this technique and hence it is useful method for repair/repair of old concrete works, bricks and masonry works which have worn out.

(6) Pressure Grouts (Cementation)

Cementation is that the process of forcing cement grout (a mixture of cement, sand, water) struggling into the structural components / cracks, gaps, fitters within the ground.

Here the eddy is drilled at selected points within the structure and cement grout of sufficiently thin consistency is forced struggling to make sure complete penetration over the cracks. This makes the structure water tight and restores stability and strength.

When the structure rests on hard but loose textured ground, its strength can be increased by this process. This technique is used for repairing structures, consolidating ground to improve the ability to create water cut-offs to prevent seepage.