Protecting buildings from negative water pressure is tricky but doable task if handled with due attention & care. Usually, waterproofing is done on positive side of water pressure but at times situation arises where there is no access of positive side to do proper waterproofing. People generally afraid of negative side waterproofing since they might have unhelpful results in past but here I want to convince that negative side waterproofing can be highly successful if executed professionally with quality chemicals or products. On the contrary, positive side waterproofing (if possible) is always recommended over negative side since it is easy to apply with higher success rates that too on relatively lesser prices.
Difference between positive and negative side water pressure
If water pressure is from the upper or inner side of concrete (pressure in swimming pool, water tanks etc.), it is positive side water pressure. On the other hand, if water pressure is from outer surface or from below the concrete (pressure due to ground water in basement), it is considered as negative side water pressure as depicted in above image. Positive side waterproofing is done in bathroom, Terrace, swimming pool, Terrace Garden, Water tanks and basements if outer surface of retaining walls accessible. If water leakages or dampness is due to ground water or due to leakage from neighbor’s bathroom and we cannot have access to other side we need to treat waterproofing from negative side.
Problems due to Negative Water pressure
Basement leakages due to ground water in surrounding soil (showed in below image), leaked drain pipes are major issues faced by basement owners. Dampness on drawing room walls due to poorly constructed neighbor’s bathroom or kitchen is another example where we have to waterproof on negative side.
How water is getting into the basements or walls?
If there is sign of water or damp patches in your basements or inside your home, solution should start from identifying the source of water. Home’s gutters and other drainage systems should be working effectively and should not be leaky. If surrounding area around the foundations encourages water to flow towards exterior walls, there would be higher chances of water related problems. Other causes are basement windows and cracks between basement walls & floor in open area. Make sure basement windows are well above the ground level and proper sealing and grouting is done in wall and floor joints in open areas.
Leakages in Gutters and drain pipes are chief reasons after ground water. Due to these reasons, basements get flooded in rainy seasons. We should test properly that these are not leaking else waterproofing can be failed due to higher negative pressures.
Why waterproofing on negative side is difficult to treat?
Due to negative water pressure, water is entering through concrete or bricks and penetrating your plaster surfaces. If a waterproofing coating is applied over it and coating does not have required flexibility and adhesion strength, it would be piled off after some time. Even if we applied a thick plaster over the coatings, it would also be cracked over the time. In such scenario, stones are applied over the coating with cement and bonding agent. Stones provide additional comprehensive strength to the coating. Moreover, not every coating is air or vapor permeable, which is a necessary requirement for a successful waterproofing. If coating does not have this features, water pressure would break it and seep through it.
Consult with architects and take quotes from multiple companies
Waterproofing is vital job in a home, since all the interiors and appearance will depend on it and would be be damaged if there is any fault in it. Hence, we should do proper research and put our efforts and involvement to have a constructive solution. Consulting with Architects and taking options from multiple waterproofing companies, can provide a right treatment and deal as well. Some waterproofing companies or contractors prefer to rely on sales strategies, not on quality works, to get the customers, so be alert for those. Prices should be one of the decisive factors before selecting any waterproofing solution treatment but not the prime and only factor.