Moisture mechanism in structures.

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Hello friends, welcome to my blog; You have to understand several concepts to be able to solve a humidity problem and it is about the pressure of the water called positive pressure and negative pressure.

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Main source of humidity in buildings

In order to understand it better, let's start from the beginning, humidity can appear in a building for various reasons; First, the most evident form of the action of humidity on a building is the water that falls in the form of rain that, together with the winds, penetrate through the openings and affect all the surfaces exposed to the elements.

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Moisture affecting nearby surfaces

Second; condensation; It is the water present in the environment in a gaseous state whose quantity increases when cooking, washing clothes, showering with hot water or the simple breathing of the inhabitants, when this vapor changes to a liquid state on cooler surfaces that normally face the outside, such as walls. and the windows generate discomfort in the residents and damage to the finishes.

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Water used to cure concrete structures.

Third; water trapped when building; It is the water that was incorporated into the home during its construction, for example, the water in the concrete, mortar, bricks, stucco preparation water, water-based paint adhesives, cleaning, washing, among others.

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Moisture by capillarity

Fourth; Rising damp from the ground also known as rising damp by capillarity; It is a continuous and constant flow of water molecules that rise from the ground on which the building is supported upwards, penetrating the construction materials that form the walls and going up them.

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Severe damage to both wall and column near a kitchen

Five; leaks in facilities; defects in installations and artifacts that lead to water such as the drinking water network, sewage, rainwater downspouts, among others.

Sixth and last; stored water, the presence of stored water is a potential cause of humidity towards the interior of the building, since any failure of the structure that contains the water can filter into the rest of the construction.

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Positive pressure in conjunction with the coating

Having clear the six ways in which humidity appears in a building, it is time to explain how it affects water pressure:

Let's start with positive pressure; When a waterproof coating is applied to a construction element, it is said that it will be subjected to positive pressure when the water is in direct contact with the waterproofing layer; Within these applications that have positive pressure, it is in the roofs and walls of the facade where the rainwater comes from the outside and is directly on the waterproofing of the roof and in the case of the walls, the rain together with the wind impacts on the paint. exerting positive pressure.

Another example is the inner walls of a swimming pool or pool where the water contained in the tank exerts positive pressure on the coating.

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Negative pressure on the opposite side of the coating

While the negative pressure of the water is when the water hits the opposite part of the support where the coating is applied, we say that the waterproofing is subjected to negative pressure when the water comes from the back exerting a force that detaches the coating.

Among the applications that have negative pressure are the walls in buried basements where the water penetrates the ground by absorption through the construction elements and damage to the finishes on floors and walls is manifested.

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Damp roof repair

It is very important to identify when it is positive pressure and when it is negative pressure of the water for the simple reason that there is no waterproofing that serves to withstand the two forces of water.

In general, humidity in ceilings or ceilings is addressed in the following way: we have a ceiling that is damp and the finish is peeling off, the origin of the humidity is the rain that falls on the terrace, filters through the slab and the water with negative pressure removes the plaster and the paint.

This moisture problem can be addressed in two ways: solve it from above where the water enters, positive compression, that is, here we stop the passage of water, first treating the joints and fissures with sealants and then proceeding with the installation of cold or hot waterproofing membranes. .

Or the other more expensive and inefficient option is to solve from below with products designed for negative pressure, these are generally cementitious and involve demolishing the finishes to apply directly to the base substrate.

In conclusion, the most important thing when tackling a waterproofing job is to identify the origin of the humidity and to know if it is a case of negative pressure or positive water pressure, all this before and in order to be able to select the correction system. adequate.

I hope the information is useful when making a decision, do not forget to support me and we will read next time, bye.

All images including schematics, photos and models are mine

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