Diagnostic investigations of reinforced concrete slabs by nondestructive methodology – thermography and debulking

La SIA S.r.l., an engineering company, offers a service of diagnostic investigations for reinforced concrete slabs aimed at detecting phenomena of piñatas’ cracking and plaster detachment. Surveys are carried out by non-destructive techniques of civil thermography and displacement carried out by specialized personnel, Engineers and Architects, licensed “UNI EN ISO 9712:2012” and “Bureau Veritas Internal Regulations IT-IND-REG-02_NDT.CIV.”


Breaking through the floor slab is defined as the detachment and subsequent falling off of the bottom of the piñatas. This phenomenon is caused by a combination of factors mainly attributable to:

-Error design of the piñata. Incorrect design of the folders causes a concentration of the stress state in the walls of the same piñata resulting in detachment of the bottom or internal rupture of the folders themselves.

-Defects in structural design. Poor floor plan regularity, excessive spans of joists or thick beams lead to increased tension in the piñatas until the mechanical strength of the brickwork is reached, resulting in its failure.

-Defects of implementation. Found mainly in cast-in-place floors, it consists of defects related to concrete segregation and/or placement with little or no cover in the joists. The breakthrough phenomenon in the present case appears to be discontinuous and spottily distributed on the slab.

-Maintenance problems. Repeated interventions over the years without a real structured maintenance program over time; this is the case with suspended ceilings, fixtures, and light fixtures that are often hung from the ceiling without any special construction precautions using makeshift techniques and materials.

It is important to remember that the phenomenon almost never occurs for only one of the reasons given but is usually the result of the presence of two or more of the above causes.

Breaking through does not pose a danger to the structure as the brick only performs the task of lightening the floor slab, however, it poses an important danger to the safety of people attending the premises subject to the phenomenon. Suffice it to say that the weight of the detached mass is between 20 and 40 kg/m2 and that often the phenomenon is not punctual but affects portions of the ceiling, e.g. for a 10 m2 detachment there is a mass of about 300 to 400 kg falling from the ceiling on people and objects in the room.


The survey service offered by La SIA S.r.l. is aimed at identifying the detachment phenomena currently occurring and identifying the causes that have triggered or may trigger the breakthrough.

The investigations consist of several moments of approaching the building and individual rooms. Propaedeutic to the investigation itself is the historical-critical analysis, aimed at the study of the construction technology used in the construction of the building, the identification of structural and non-structural interventions, which have characterized the maintenance during the life of the building; this knowledge is achieved through the study of the original plans and documentation found and provided by the client.

Following the preparation of an accurate and detailed investigation plan for the building under consideration, the site survey is carried out, which consists of the following operational steps:

-Preliminary visual investigation aimed at identifying deterioration, active or past seepage, cracking framework.

-Thermographic survey for further investigation of what was found in the visual survey and identification of the warping and positioning of the joists.

-Exploratory surveys generically performed through small cores and endoscopies in order to confirm the type and stratigraphy of the brickwork.

-Manual tapping on 100 % of the soffit surface of the floors with the identification of particular areas of interest that showed uneven behavior with respect to the floor type.

-Instrumental beating by sonic-acoustic acquirer performed at prepared stations on a grid established according to the floor plan. In addition, all areas that showed abnormal behaviors during manual beating are deepened.

-Check condition and load tests on the anchorage systems of all bodies hanging from the ceiling (suspended ceilings, fixtures and lamps).

From the analysis of instrumental beating, in accordance with relevant regulations and conventions used, bands of degradation analyzed with diagnostic methodology can be identified:

-Non-significant risk (attic in good condition)

-Low risk (visual defects or micro surface cracks limited to plaster layer only; infiltration not recent and/or localized)

-Medium risk (superficial cracks and fissures on plaster without particular signs of decay, presence of infiltration, even diffuse)

-High risk (obvious detachment of the soffit with swelling of the plaster; cracks and crevices widen and/or move during beating in areas adjacent to the detected damage; there is a real risk of falling material)

-Dissolving in place (presence of the phenomenon of breaking through; obvious detachment of the soffit with plaster swelling; cracks and crevices widen and/or move conspicuously during beating in areas adjacent to the detected damage and material falls during investigation)

The last step of the service is to prepare tables and technical reports with graphic and color identification of the anomalies found. Through the degradation bands listed before, singular or entire areas affected by the phenomenon are highlighted, and both the crack pattern and seepage visible to the naked eye or by infrared survey are reported.

The study thus conducted ends with conclusions and considerations that identify the possible reasons that led to the criticality and the status and extent of the anomaly found.

You can also follow the following links for further discussion:

Qualification levels UNI EN ISO 9712

Peeling and falling plaster in attics: risk indicators for building maintenance (part 1)

Peeling and falling plaster in attics: risk indicators for building maintenance (part 2)

Deflection of floor slabs (latero-concrete): Analysis of causes, diagnosis and interventions

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