At first we will learn about ground water control according to IBC. Where it is found that ground water table is at equal or more than 152mm below lowest level of floor (bottom level), the floor and foundation wall as well need not to waterproofed i.e. damp proofing is enough according to recommended material and method of IBC.
When not found at desired elevation, proper control system can be adopted to lower ground water level according to following discussion:
Design of ground water control system to lower the water table should be based on standard and approved principles of civil engineering considering at least following:
• Permeability of soil
• Rate of entrance of water to designed drainage system
• Expected and maintained capacity of the pumps
• Head of operation of pumps
• Rated discharge capacity of disposal area In the ground water control system.
Again walls that will be treated or constructed should be of concrete/masonry; should be strong enough to withstand expected hydrostatic pressures, along with other lateral pressures/loads that are active in the walls.
Here hydrostatic pressure is considered as waterproofing term, when hydrostatic pressure condition dominate in the field and design of ground water control not include or not enough to lower expected elevation (as discussed above).
We know due to imperfection of concrete, formwork sealing and improper mixed or proportioned concrete, the surface of concrete member have some defects. We have discussed many posts about such imperfection of concrete work. However, our concern is here surface preparation; we are not discussing much about imperfection.
Before applying water proofing materials on surface of concrete walls, the imperfection like recesses or holes appeared after removal of formwork or any types of cracks (if not structural cracks) should sealed using bituminous materials or other accepted materials or method also can be used in this purposes.
In case of masonry walls, the exterior walls under ground level should be covered with plaster; may be of cement plaster or with other suitable material. The recommended thickness should be equal or more than 9.5 mm (3/8 inch) when mortar of Portland cement is used.
The plaster should used to masonry footing too. Now think about waterproofing, this should be used from top or above of maximum level of ground water table to bottom of wall. The IBC recommended to keep waterproofing more than 12” above of ground water table. The rest portion of wall should be damp proofed according to IBC as discussed in previous post.
Water proofing material (IBC)
Should consists of two ply hot mopped felts, equal or more than 6 mil polyvinyl chloride, polymer modified asphalt of 40 mil, 6 mil thick polyethylene or another approved materials or methods that is capable to bridge non-structural cracks. Sealing and lapping of joints in membrane should be provided according to installation instruction of manufactures.