Box Type Waterproofing
This type of water proofing system is used only for basement waterproofing or waterproofing structures below the ground level from outside to prevent leakages of subsoil water into the basement. This method is quite popular with some designers and effective even now.
In this method stone slabs (Kota or Shahabad Stones) are first laid in the excavated pit over blinding concrete in a staggered joint fashion to avoid the continuity of the mortar joints. The joints are effectively filled with rich mortar admixed with integral waterproofing compound and cured. Over this the raft is laid and shear/brick walls constructed. The slabs are erected around the walls in a similar fashion leaving a gap of one to two inches between the external surface of the wall and the inner face of the stone surface. The joints again effectively sealed with rich admixed mortar and the same mortar is filled in the gap between the wall and the stones. This stonework is continued up to ground level. In this system the raft and the sidewalls are protected from direct exposure to sub soil water.
This system works on two principles of common sense. First the area exposed to subsoil water is only the area of the joint where as the whole stone is impervious to water, hence only a fraction of area, that is, that of the joint is exposed to subsoil water, when the joint itself is filled with rich and quality mortar. Secondly, the path of water to reach the raft or the sidewall is elongated. This elongated path is through quality mortar. This system seeks to delay the occurrence of leakages in the basements. A lot of building structures are waterproofed by this system.
Floor Installation
- Preparation of surface by cleaning, leveling etc.
- 20 mm thick cement-sand-mortar mixed with water proofing powder, 4% by weight of cement shall be laid on PCC and 20 mm graded aggregate free from impurities shall be spread on the floor. It shall be cured for 3 days.
- Provide insert sockets and pipes to release the sub soil water pressure.
- Then 18-20 mm thick stones ( Kota or Shahbad) of approximate 600 x 600 mm in size shall be laid flat and joined with cement-sand-mortar. This shall project 300 mm all around RCC raft. The stones shall be hard tough and free from cracks.
- Then the surface shall be screeded with cement-sand mortar and finished smooth.
- RCC raft, walls or masonry shall be constructed as designed.
- The sockets / pipes are grouted with pressure.
- Columns or any support etc. coming out of raft shall be sealed with poly-sulphide sealant at PCC level and at top of raft
