The stresses transmitted by the foundations to the ground, along with other factors such as the type of soil, or the presence of water, roots, etc., can lead to deformations that result in settlements, horizontal displacements and rotations of the structure. If these are excessive, exceeding tolerable levels, they can cause a loss of functionality, producing cracks and fissures.
The difference between the two is that fissures are the result of superficial openings that only affect the material covering a surface, while the appearance of cracks in walls and slabs is an unmistakable symptom of a building stability problem that should not be underestimated. Cracks in walls can be of varying depths and lengths, and can occur in both interior and exterior walls, load-bearing walls, and partitions.
How to eliminate cracks in walls?
Before repairing cracks in the wall or plaster, it is necessary to identify the cause of the problem because intervening directly on the walls by superficially painting without understanding the cause could be just a useless expense that would not solve the problem.
Cracks in walls, fissures in pavements and slabs, and doors and windows that don't close properly are just some of the signs of foundation settlement as a direct result of changes in the underlying ground. Concern is growing, and the question is why? Why are even buildings that were once considered stable now beginning to experience settlement problems and cracks in their walls?
The causes of these cracks are varied and, in general, can be due to expansion, humidity, poor quality materials, improper application of coatings, and errors that can occur during both the design and construction phases. Sometimes the causes lie in a context where humans have no control: nature, and especially climate change and seismic events.
As for the climate, long periods of rain and severe droughts typically alternate; this is a lethal change for even the most stable buildings, and the reasons lie in the geology of the area. Most settlement phenomena are due to the process by which the volumes of soil belonging to the surface stratum, which normally do not interact with the foundation, extend their susceptibility to a depth of 5-6 meters from ground level.
In other words, buildings are affected by an increase in the volume variations of land adjacent to the surface with consequent reactions that are triggered in the mechanisms that regulate the stability of the soil and the equilibrium of the overlying construction and the last of the indications is the appearance of dangerous cracks in the walls or the walls of the buildings.
Causes of cracks in walls and partitions
Before discussing how to eliminate cracks in walls, it is necessary to understand why these cracks appear and what types there are:
Differential settlement occurs when the support beneath the wall deforms unevenly. This can be the ground, a beam, a floor slab, or a combination of several elements.
Vertical and horizontal cracks occur when loads are greater than the wall can withstand (due to errors in dimensioning, execution, or the appearance of unforeseen loads).
Diagonal cracks are the most dangerous because they indicate serious structural damage that requires consultation with an expert or specialist to determine the cause of the cracks in the walls and thus repair the structure.
The expansion of a wall often causes cracks in other walls attached to it at an angle, such as at facade corners. These cracks are usually wider at the top of the wall. The contraction of a wall causes cracks within it, and as it contracts, it generates horizontal tensile stresses. These stresses are also generated vertically, but the wall's own weight usually counteracts them.
In some cases, the cause of cracks appearing in the walls could be structural, due to poor design or construction, but in most cases the cause may be the nature and/or inadequate maintenance of the property.
Seismic events, drought, and climate change are some of the natural causes that can disrupt the balance between foundations and the underlying soil. These phenomena can be destructive and affect the building's safety. Sometimes they are rapid and destructive movements, as in the case of earthquakes, or slow and progressive, as in the case of climate change, which weakens the surface soils on which buildings are built. In both cases, cracks can appear in walls, requiring intervention to ensure the building's safety.
Cracks in interior walls can be caused by water seepage into the ground, which, over time, alters its composition. Initially, dampness and mold may appear on the walls, but as time passes, doors will begin to open and close with difficulty, and the first cracks will appear in the floor. The phenomenon will then spread deeper, reaching the ground beneath the foundation, and cracks will appear in the walls.
The same applies to cracks in exterior walls, and these structures can also be affected by strong vibrations due to heavy traffic in the vicinity, by the action of the roots of tall trees, by water seepage or by excavations close to the foundation.
The origin of settlements on the land
In the field of geotechnical engineering, settlement is a downward vertical movement of the ground (subsidence) due to the application of different types of loads that produce a change in soil stress. To better understand the reasons for ground settlement, it is necessary to analyze the physical composition of the soil.
All soil is multiphase: it has solid, liquid, and gaseous phases, and the solid phase, in particular, is affected by the presence of water and voids, as well as their variations over time. When soils and clays come into contact with large quantities of water, they fill and expand, increasing their volume and generating an imbibition phenomenon. During hotter seasons and in cases of drought, soil volumes contract, generating a drying phenomenon.
The cyclical nature of these phenomena affects the delicate balance of the foundation and the structure above it. Foundations, as we know, support the structure on the ground, and differential settlement means the structure is yielding, losing the horizontality of its frames. This has a very evident consequence on the building's structure: when the stress reaches its limit, the building first deforms, then sinks, and dangerous cracks appear in the walls.
On the other hand, increasingly frequent seismic events weaken the soil/foundation system and building structures, causing instability and dangerous cracks in walls. Good underlying soil with favorable geotechnical characteristics is the best starting point for effective seismic retrofitting of buildings, ensuring the safety of occupants and preserving the property's value.
How to eliminate cracks in walls?
As indicated above, before intervening with works on the walls to restore the previous state of the affected walls, it is necessary to consolidate the ground underlying the foundation or to carry out a consolidation of the foundations.
The consolidation of the ground underlying the foundation consists of intervening by reinforcing the ground that supports the building to improve its load-bearing capacity and restore the necessary stability and safety conditions, and is carried out with injections of expansive resins.
These are fast, effective, decisive, and minimally invasive solutions that don't require excavation, demolition, or lengthy and complex construction work. Today, these technologies are extremely reliable and are increasingly used for rapid interventions, even in confined spaces, to minimize disruption to buildings and their occupants.
The special expansive resins, perfectly compatible with the soil and the environment, guarantee effective results over time. SEE&SHOOT® is a procedure, regulated by European patents, whose application procedures have obtained a Positive Technical Opinion from ICMQ (the most prestigious Italian Institute for Certification and Inspection in the construction sector) according to the EN ISO/IEC 17020 standard. This opinion recognizes that these procedures, within the field of observation methods provided for by the Technical Regulations for Construction for addressing the behavior of the building-soil system on-site, can be a useful and precise reference for the Geosec® network to determine the correct procedures for soil consolidation using this technique.
Foundation consolidation, on the other hand, involves directly intervening in the foundation structure. There are different systems, the most common being piles, micropiles, driven micropiles, and widening the foundation footprint. Driven micropiles are the least invasive and fastest solution for repairing cracks in walls, as the intervention aims to transfer the stresses transmitted by the foundation to the competent soil layers.
Micropiles are composed of special modules made of structural steel, coupled together and driven into the ground under pressure, without vibrations, using hydraulic jacks. The self-weight of the foundation (slabs, pile caps, or beams) acts as the reaction force against the hydraulic jacks. The driving pressure on the different modules that make up the micropile is applied until the design load of the micropiling project is reached.
Source: GEOSEC ground engineering
