Dampness is one of the most common and persistent issues that can affect the structural integrity, aesthetics, and overall comfort of a space you are either working in or living in. Now you might be wondering what is dampness. The presence of gravitation or hygroscopic moisture is commonly called dampness. It is one of the main criteria that any good construction should be free of dampness. It should not allow moisture through any of the floors, walls, or even roofs.
The moisture that enters through various cracks of roofs walls and floors can give rise to multiple unhygienic conditions which include deterioration of the building structure while also decaying the components as well. Hence it is very important to prevent dampness from entering the entire structure no matter where. Every structure should be damp-proof. Damp proofing is also a part of the building design and it should be included right from the planning and construction of the building.
Causes of dampness
Causes of dampness if well known then there are chances that you can avoid any moisture entering the building. Here are some of the causes of dampness that tend to lead to the destruction of multiple good structures:
- One of the main causes found to be is the high groundwater table which affects the foundation. At times the building materials used in the foundation also tend to absorb the water from the ground by an action called capillary action.
- If the external walls of the building are not protected with damp proof methods, then there are chances that building walls may absorb some rainwater.
- If the structure is built in an isolated area where there is no proper drainage option then also the moisture can collect up and deplete the materials used for the building.
- Most of the newly constructed buildings tend to be damp for quite a while after it is constructed.
- If there is a very flat slope of the roof then that may also lead to penetration of rainwater especially if it is temporarily stored on the roof.
- The compound walls and parapet walls should be provided with a damp proofing course on the tops that are exposed. Otherwise, there are chances that dampness may enter through the exposed part of the top area and may lead to serious troubles.
Effects of dampness
If people know what is dampness, then there are high chance that they also know what are severe effects of dampness are that may lead to even destruction of the entire building. Here are some of the commonly seen effects of dampness:
- The plaster applied may become soft and result in crumbling down.
- Electric fitting of the building may be damaged
- Damages paints applied on the walls
- The continuous presence of moisture may lead to efflorescence which may also disintegrate bricks, stone, and tiles.
- The steel that is used in the foundation of the building may become corroded.
- The materials used for floor covering may also be seriously damaged
- Increase in the breeding of mosquitoes
- Growth of termites
- Unhealthy conditions that are not optimal for occupants can be observed
- Non-aesthetic patches may be seen on some beautifully painted walls and ceilings.
- Wooden furniture and components such as doors and windows can become damaged if they are exposed to moisture.
Preventing dampness
The most common methods to prevent dampness can be provided as follows:
- Integral waterproofing method
- Special devices used such as providing cavity walls and chajjas
- Surface treatment using a damp-proof paint
- Providing DPC also called as Damp proof course
Damp-Proof Course (DPC)
Multiple people are not exactly familiar with what is damp proof course. A damp proof course is basically essential to install, particularly at the basement level or at the foundation of a building while construction takes place. It tends to prevent any moisture levels from rising through walls and floors.
Excessive moisture can often lead to severe damage to properties. It also makes sense to know some damp proof treatments in such cases. Effective DPC normally guarantees that the water level stays away from the ground.
Homeowners need to invest in good damp proof courses. At times if this is not immediately applied then there are chances that moisture could severely damage both plaster and may cause discoloration. The damp proof course should be 150 mm above the ground. Plastic DPC or bitumen are the most commonly used materials for mortar courses. If this is not implemented, the level of groundwater may rise above the DPC levels after renovation and the moisture may enter the structure.
Materials for DPC
Various materials are used for DPC and can be given as follows:
1. Mastic asphalt: It is a semi-rigid material that provides an impervious layer for damp-proofing
2. Hot bitumen: It is quite a flexible material which is usually placed over either mortar or concrete
3. A combination of bituminous felt and sheet
4. Metal sheet: There are various sheets of Aluminium, copper, or lead which are usually used as a part of the damp proof course.
5. Bituminous or asphalt felt: This is a material that is quite flexible and is available in rollers of wall width. It is also easy to lay and lay it on the cement mortar
6. Bricks
7. Stones: If stones such as slates and granites are added to cement then they may help in damp proof course
8. Mortar
9. Cement Concrete: Cement concrete should be of a ratio of 1:2:4 to say it is a good damp proof course. It is also generally provided in the building at the plinth level
10. Plastic sheets
Plastic sheets are really good for damp proofing courses. They are usually made up of polyethylene having a thickness normally up to 1 mm.
Types of DPC
If you are looking at ways of preventing dampness then one of the sure shot ways is to get damp proofing done. A damp proof course tends to prevent the entry of moisture into the building. Damp proofing can be easily done with the help of various types of DPC and can be provided as follows:
1. Usage of DPC: Membrane Damp proofing
This method consists of the introduction of a water-proof membrane or a DPC also called a damp proof course between the part of the structure where moisture is likely to affect and the source of moisture.
The damp proof course may also include multiple flexible materials such as bituminous felt, plastic sheets, cement concrete, mastic asphalt, metal sheets, etc. The damp proof course can either be applied vertically or horizontally on the walls, floors, etc. which are highly open to damage by dampness.
2. Surface chemical treatment
In these methods, a layer of water-repellent chemical compound is applied onto the affected area through which moisture usually enters. For surface treatment, water-repellent compounds such as metallic soaps like Aluminium and calcium plates along with stearates are highly useful.
It should also be noted that the surface treatment for dampness will work only when the moisture is on the surface of the structure and is not under any pressure. Even the surface of exposed brick or stone walls can be easily sprayed with these water-resistant compounds if it is highly needed.
3. Cavity wall construction
Cavity wall construction is a useful way of preventing dampness. In this method, the primary wall of a building is protected by an outer skin wall while leaving a small gap or cavity between the two.
4. Integral damp proofing
In the method of integral damp proofing which is one of the common ways of preventing dampness, a mixture of certain water-proofing compounds and concrete is mixed and applied onto the area where the moisture has affected. This mixture when applied to the surface of the structure tends to form an impermeable layer which makes it hard for moisture to enter the wall. These compounds are available in three types as follows:
- Compounds that are made from talc or chalk may fill up concrete voids using the mechanical action principle
- Compounds such as oils, petroleum, fatty acids, or soaps work on the water repulsion principle. These are mixed with concrete to make it water-repellent.
- Compounds like aluminium sulfate alkaline silicates or calcium chlorides tend to react with concrete in order to create waterproof concrete.
5. Pressure Grouting
Pressure grouting is a method where cement grout is forced to enter the voids, cracks, and fissures that are present in a building under pressure. The components of a building that are prone to moisture penetration are joined and made resistant to the entry of water. This method is quite effective and it usually gives good results. Pressure grouting can also be used for cracks of various sizes and lengths apart from various depths.
6. Guniting
In this particular process, an impermeable layer of rich cement mortar is added under pressure over the exposed surfaces to make them waterproof. It is normally used in pipes, and cisterns where there is high water pressure. The cement mortar used for guniting usually consists of sand and cement in the ratio of 3 parts of sand to 1 part of cement. This mixture of cement and sand is added onto a clean surface using a cement gun under a pressure of 2 to 3 kg per cm square.
The nozzle of the equipment is usually kept at a distance of about 75 cm to 90 cm above the surface. The mortar is mixed and then applied after which it is cured for at least 10 days to get maximum strength.
Selecting DPC materials
The choice of material that is used to function as an effective damp-proof course requires a thoughtful selection. It depends on various factors such as atmospheric and climatic conditions, the nature of the structure, and the situation where DPC needs to be provided. The points to be kept in mind while selecting materials for DPC can be provided as follows:
1. DPC materials used for floor roofs:
In the case of large areas such as under floors and over roofs are supposed to be covered by DPC, bitumen felts, or mastic asphalts. But you need to ensure that the joints are scaled and lapped properly.
2. DPC for situations where different thermal conditions apply:
In the case of parapet walls, the materials to be used can include bitumen felts, lead sheets, copper sheets, and mastic asphalts. However, you need to ensure that the DPC materials are flexible enough to allow slight movement due to the structural settlement.
3. DPC for above-ground levels:
In normal buildings, plinths are usually provided above the ground level. For DPC above ground level, different materials can be used. At the plinth level, a 40 mm to 50 mm thick layer of 1:2:4 cement concrete is treated as one of the best materials under normal circumstances. When more damp conditions are present, rich mixed concrete can be used. Some of the waterproofing materials such as pudlo, impermo can also be used to make concrete thicker. Normally only one or two layers are applied to the surface of the concrete layer.
4. DPC material for cavity walls:
In the case of cavity walls, it is highly recommended that flexible materials such as lead strips, copper strips, and bitumen sheets be used for DPC. As the base level of the cavity where the foundation of the cavity is situated materials such as bituminized felt or ordinary mastic asphalt can be used.
Installation of DPC
The general principles that need to be followed while laying a damp proof course can be provided as follows:
- The DPC should cover the entire thickness of the walls excluding the rendering part.
- When a horizontal DPC is to be continued up a vertical face, a cement concrete fillet of about 75 mm in radius should be provided at the junction before the treatment is done.
- The mortar bed onto which the DPC is laid should be perfectly leveled and must have no projections. The uneven base will most probably create a lot of damage.
- Each DPC should be placed in correct relation to other DPCs to make sure that there is a complete and continuous barrier to the passage of water from roofs, floors, or walls.
Conclusion
Now that you have understood what is dampness it is important to find out the areas where moisture is likely to enter through and to rectify it right away. You might also want to use some of the dampness inspection services that are commonly available to detect any problems in your housing areas. You can also detect it with some of the visible signs and treat it right away!
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