Any material used as a DPC must have the following properties. they should be
- Strong and durable to register loads
- is dimensionally stable
- Free from Salt Lake Sulfates, Chlorides and Nitrates
There are usually 4 types of materials that can be used in DPC
- Flexible materials (bitumen felt, plastic sheeting, etc.)
- Semi-hard material (mastic asphalt)
- Hard material (brick, stone or concrete layer)
- Grouting material (cement slurry)
But the following three points should be considered before choosing any of the above materials and then the choice has to be finalized.
- Climate and atmospheric conditions
- nature of structure
- Construction Components where DPC is to be provided
Some of the key points are mentioned below which will help you in selecting the material to use as damp proof course or DPC.
1. DPC material above ground level
Generally cement concrete is used as DPC above ground level. This type of DPC is implemented at the plinth level. For normal climatic conditions a 25 to 50 mm thick layer of cement concrete of grade M15 (1:2:4) can be used.
A higher grade of concrete can be used as a DPC for damp and damp conditions.
when designing concrete; A waterproof material like puddle or impermo etc. can also be added to make the concrete more impervious.
For better protection, apply two coats of hot bitumen to the dry surface of the concrete.
2. DPC material for floors and roofs
In the case of flat or large areas (such as floors and ceilings) or the thickness of the walls exceeding 40 cm, it is advisable to use a flexible or semi rigid type of DPC material. Because this type of material has less number of joints.
Any flexible material such as mastic asphalt, bitumen felt or plastic sheet can be used.
When using these materials as DPCs, ensure that they are properly bonded to the surface and that all joints are properly sealed.
3. DPC for areas experiencing differential thermal movement
Differential thermal movement occurs when two building components that are joined together (such as parapet walls and ceilings) experience different amounts of expansion.
In these cases the use of a flexible type of DPC material such as mastic asphalt or bitumen felt is a good option.
4. DPC Materials for Cavity Walls
In case of cavity wall construction, the cavity above the door or window should be filled with flexible material such as bitumen felt or strips of lead, etc.
5. DPC for expansion and contraction joints
If expansion and contraction joints are present in the retaining walls of RCC slabs or basements, they should be sealed using PVC or GI sheets. This will prevent the movement of sub-soil water into the building.
Building Construction by Sushil Kumar