Positive side applied waterproofing is an external waterproofing system. Waterproofing system installed to the exterior face of the below ground structure.Suitably designed positive system can protect the structure and the interior against the effects of moisture and pressurised water. Positive side applied system takes the water pressure in conjunction with the structure to which it is applied to effectively create a permanent consistent barrier.
What is negative side waterproofing ?
Negative side applied waterproofing is applied to the internal surfaces of the structure, usually when there is no access or ability to either get access to the access to the external surfaces or where continuity is not possible. An internal negative side system is often reliant on the ability of those surfaces in accept the waterproofing treatment. General rule of thumb is that an internally applied system is as good as the sum of the integrity of the structure and the preparation undertaken.
Negative side waterproofing in some instances has the capability of dealing with an incredible 13 bar pressure (this equates to just over 130m head of water)!!
Both positive and negative:-
Waterproofing systems have pro’s and con’s – For example, a piled structure cannot be waterproofed on the positive side and it is also difficult to waterproof structures where access is limited. Internal waterproofing for example, can be applied to piled structures because access is not a problem and continuity is not a problem.
Full site investigations are important when mitigating and reducing risk in waterproofing design. The results will have a bearing not only on the design but on the waterproofing system itself (positive (external)/negative (internal). Whilst findings of a site investigation are often seen as conclusive, it needs to be remembered that this is just a ‘snapshot in time’. It should be assumed that water will come to bear against the full height of the below ground structure at some time in its life.
The system designed may be acceptable at the time of construction meeting the ‘snapshot in time’ investigations, however this system may not be adequate for environmental changes of the future.
The decision to use positive side or negative side waterproofing can be made after exploring:
* Changes in water tables
* Changes in hydrostatic pressure
* Thermal changes
* Dynamic Movement
* Heave * Subsidence * Clay soils * Changes in environment
* Stress
* Changes in ground drainage
* Structural stability
* Changes in hydrostatic pressure
* Thermal changes
* Dynamic Movement
* Heave * Subsidence * Clay soils * Changes in environment
* Stress
* Changes in ground drainage
* Structural stability
