Examining the cause, effect and remedy of hydrostatic pressure.

If you have heard the expression that ‘water will always find a way’, then it is never more relevant than when discussing Hydrostatic Pressure. The term Hydrostatic Pressure is often misused when assessing flooring related failures, there are many other reasons for failures due to moisture related issues. By definition it is described as the pressure of a fluid at equilibrium within a fluid due to the force of gravity.  You can liken this to the pressurised conditions of the ocean the further you descend.

Slabs above ground cannot suffer the effects of Hydrostatic Pressure, concrete slabs below the water table, and properties that obstruct the natural flow of water, on a hillside for instance are most at risk. Hydrostatic Pressure can manifest itself in many different ways, for example in basements, efflorescence build-up on walls, extremely high humidity, pools of water on the floor and fungal growth. It is important to determine whether the surrounding landscape is subject to pooling of water after heavy downpours, this could be a sign of a high water table and saturated soil.

Water is a heavy and dense substance, weighing in at around 60Ibs per cubic foot. If poor drainage allows water to pool against a foundation wall of a property the build-up of pressure can be immense and it is only a matter of time before water finds a small crack and inevitably a pathway into the building. If it is an older property (pre 1965) then the slab is unlikely to have a structural DPM installed underneath. Earlier slabs can be very porous due to a variety of reasons, they may have been mixed on site leading to indifferent water/cement ratios, poor compaction and curing methods. This will undoubtedly let moisture vapour pass through easily, couple this with the effects of Hydrostatic Pressure and you’re in for a world of endless moisture related flooring issues.

A surface applied Epoxy DPM system, will not on its own, solve this problem.  In extreme cases Hydrostatic Pressure can buckle walls and lift slabs causing catastrophic failures. Until the external issues are dealt with in terms of installing better drainage systems that can divert water away from the building, then it can be expected that continuous flooring failures will occur.

To conclude, it is always beneficial to take a look at the surrounding environment and ask questions about any flooding history when trying to get to the root cause of reoccurring flooring failures, and if any of the above issues are detected then they could be the signs of the force that is Hydrostatic Pressure at work.

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