Dampness in Buildings and DPC (Damp Proof Course)
Types of Floor Lecture Notes
The access and penetration of moisture content into building through its walls, floor, roof etc. is called dampness in buildings.
Effects of dampness in buildings:
- Causes rotting of wood.
- Causes corrosion of metallic fixtures.
- Deteriorate electric installations.
- Deteriorate carpet & furniture’s.
- Causes spots on the floors and walls.
- Causes petting off and removal of plaster.
- Causes bleaching and blistering of paints.
- Causes efflorescence in bricks, tiles and stones
- Dangerous for the health of occupants.
- Reduces the life of structures
- Promotes growth of termites
Causes of dampness in buildings
- Rain penetration
- Level of site
- Drainability of soil
- Climate condition
- Defective orientation of building
- Moisture entrapped during construction
- Defective construction e.g. joints
- Use of poor quality bricks which ultimately absorb a lot of water.
- Use of Poor quality of concrete (permeable concrete)
Methods of preventing dampness in buildings
- By providing DPC ( Damp proof course )
- By surface treatment i.e. by providing damp proof paint
- By integral water proofing method
- By special devices i.e. by providing chajjas & by providing cavity walls etc
This is provided in internal side of roofs
- For decoration
- For preventing dampness
DPC - Damp proof course
It is continuous layer of impervious material applied to prevent moisture transmission. A common example is polyethylene sheeting laid under a concrete slab to prevent the concrete from gaining moisture through capillary action. A DPM may be used for the DPC.
Rising damp is caused by capillary action drawing moisture up through the porous elements of a building's fabric. Rising damp, and some penetrating damp, can be caused by faults to, or the absence of a damp-proof course (DPC) or damp-proof membrane (DPM).
- For internal wall we only provide horizontal DPC ( 175 kg/cm 2 standard pressure for bitumen )
- Three layers of bitumen is provided
- You should provide a mortar layer before DPC
Types of DPC
There are two types of DPC
- Flexible DPC: It is DPC when load doesn’t crack e.g. Polythene and Bitumen
- Rigid DPC: It is DPC when loaded; it cracks e.g. Rich cement concrete 1:2:4
- Bitumen mastic: Bitumen mix with fine sand
- Bitumen felt: It is available in the form of rolled sheets
- Hard laid bitumen
- Metal sheets
e.g. Lead, copper, aluminum is provided with mortar, to avoid rusting.
Rigid DPC: It is DPC when loaded; it cracks e.g. Rich cement concrete 1:2:4