ABNT NBR 7200 - Execution of wall and ceiling cladding with inorganic mortars - Procedure

Regulatory References:

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• NBR 5732 - Ordinary Portland Cement - Specification
• NBR 5735 - Portland Blast Furnace Cement - Specification
• NBR 5736 - Portland Pozzolanic Cement - Specification
• NBR 6118 - Design and Execution of Works of Concreto Armed - Procedure
• NBR 6453 - Virgin Lime for Construction - Specification
• NBR 7175 - Hydrated Lime for Mortars - Specification
• NBR 10907 - Masonry Cement - Specification
• NBR 11578 - Portland Composite Cement - Specification
• NBR 12989 - White Portland Cement - Specification
• NBR 13529 - Inorganic Mortar Wall and Ceiling Cladding - Terminology
• NBR 13749 - Inorganic Mortar Wall and Ceiling Cladding - Specification

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First Stages:

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Here, we will talk about the steps determined by NBR 7200, which deal with some actions that must be adopted and conditions that must be considered to carry out an efficient coating execution process, which we will see below.

1. Preliminary checks: consists of inspecting the condition of the base in order to determine the corrections necessary for the execution of the coating. Thus, the use of special tools must be observed; period in which the service will take place; assessment of the ergonomic conditions of the workplaces, verifying the need for scaffolding or other equipment; adaptation of the construction site to the installation of the equipment and execution of the services. In addition, the site must have a structure for preparing mortars, containing a mechanical mixer; separate and identified compartments for storing the different materials; piped water point; sieves and devices for measuring aggregates, additions and water.
2. Execution schedule: here the minimum ages (curing times) of mortars prepared in construction sites are determined. They are: 28 days of age for concrete structures and structural reinforced masonry; 14 days of age for structural unreinforced masonry and masonry without structural function of bricks, ceramic blocks, concrete blocks and cellular concrete, assuming that concrete blocks have been cured for at least 28 days before use; three days of chapisco's age to apply Emboço or single layer; for hot and dry climates, with temperatures above 30°C, this period may be reduced to two days; 21 days of age for Emboço of lime mortar, to start the services of plastering; seven days old of Emboço of mixed or hydraulic mortars, to start the services of plastering; 21 days of coating age of plastering or single layer, for performing decorative finishing. For industrialized mortars, these deadlines may be changed if there is a specific instruction from the supplier.
3. Follow-up of coating services: consists of recording in service monitoring spreadsheets of the conditions for applying the coatings for the preparation of the report regarding: level, plumb and flatness conditions of the base; treatment of the base to correct level, plumb and flatness; cleaning the base; tracing and preparing the mortars; thickness of the coating or layers of the coating and any corrections or repairs carried out during the service.
4. Cleaning and protecting other services: when performing the cladding service, it is important to take care that it does not damage other services performed, such as the other components of the building.

Now, shall we understand the steps of performing mortars on surfaces?

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Execution Stages:

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Preparing the coating base

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The NBR 7200 includes concrete cladding bases, bricks and ceramic blocks, concrete blocks, cellular concrete blocks, and silica-limestone blocks. The bases must meet the requirements for flatness, plumbing and leveling established in the respective standards for masonry and concrete structures. The presence of moisture seeps must also be observed, which must be eliminated before proceeding with the other base preparation procedures.

The preparation of the coating base can be divided into correcting irregularities, different contiguous bases and cleaning the base. The correction of irregularities consists of leaving the surface even to receive the mortar. Thus, it is necessary to remove iron tips from the parts, burrs between masonry joints, as well as to correct depressions, holes and tears. If the base is composed of different materials and is subjected to stresses that generate considerable differential deformations, metallic, plastic or other similar material must be used to join these materials, creating an area capable of withstanding the differential movements to which it will be subject.

And finally, the cleaning of the base surface must be carried out, since it needs to be clean, free of dust, grease, oil, efflorescence, loose materials, or any products or incrustations that may impair the adhesion of the coating. The standard describes how cleaning procedures should be performed according to each type of material to be removed. In this article, we listed them all, take a look!

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Preparation of inorganic mortars

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The preparation of mortars can be divided into: composition of mortars, measurement of materials and preparation of the mixture.

First, the trace of the mortar must be established by the designer or builder, in accordance with the project specifications and the conditions for carrying out the coating services. The trace must be expressed in mass and the consumption of the materials must be recorded in the accompanying sheet. Thus, with the established mortar trace, it is possible to list the quantity and what materials will be needed for the execution of the service.

After this stage, the materials are measured and can be performed in volume, and the builder is responsible for converting the specified trace into mass. The measurement of materials in volume must be performed using containers of known volume and identified through the use of different colors or clearly distinct symbols. In addition, the measurement of materials with instruments or containers that do not ensure a constant volume, such as, for example, dosing with a shovel or in cans, must not be allowed. Thus, for an accurate measurement, the amount of aggregate and additions must be corrected according to the variation in humidity, in order to obtain mortars with the same workability and proportionality.

After measuring the materials, the mixture is prepared, in which the mortars must be mixed by a mechanized process or, in exceptional cases, by manual process, until a perfectly homogeneous mass is obtained. In the mechanized process, the mixing time must not be less than 3 minutes and not more than 5 minutes, while in the manual mixing process, mortar volumes of less than 0.05 cubic meters must be prepared at a time. The NBR determines how lime or mixed mortars are prepared, which require another type of mixture.

When preparing mixed mortars, cement must be added at the time of its application, given the maturation period of the slurry or lime-sand mixture. When preparing industrialized mortars, it is necessary to follow the manufacturer's instructions. In addition, the production site must have silos or storage containers that are watertight, protected from rain and insolation.

Finally, the production volume of cement or mixed mortar must be controlled so that it is used within a maximum period of 2 hours and 30 minutes. For temperatures above 30°C, strong direct insolation over the mortar stock, or relative air humidity of less than 50%, the deadline must be reduced to 1 hour and 30 minutes. These established deadlines may be changed by the use of retarding additives, following the previously studied recommendations for use.

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Application of mortars

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According to NBR 7200, mortar coating services must begin with the completion of the coating system project and after completing the previous steps mentioned above.

Each candidature The application of a new layer of mortar requires, depending on the purpose and weather conditions, the humidification of the previous layer. In addition, the coating mortar must not be applied in environments with a temperature lower than 5°C and at temperatures above 30°C, special care must be taken to cure the coating, keeping it moist for at least the initial 24 hours through the constant sprinkling of water. This same procedure must be adopted in situations of low relative air humidity, strong winds or strong and direct insolation on the covered planes.

The execution of a plastering or single-layer coating must meet the thicknesses contained in the coating design and comply with the requirements established in NBR 13749.

The coating plane will be determined by means of reference points arranged in such a way that the distance between them is compatible with the size of the ruler to be used for battering. At these points, taliscas of flat pieces of ceramic material must be attached, with mortar identical to the one that will be used for the coating.

Once the coating plane has been defined, strips are filled in between the taliscas, using mortar, which will be regulated by the passage of the ruler, constituting the guides or masters.

After the guides or guides have hardened to allow the ruler to be supported for the scouring operation, the mortar is applied and thrown onto the surface to be coated, with the aid of a mason's spoon or through a mechanical process, until the desired area is filled. In this same operation, the taliscas must be removed and the voids filled.

Once the area is completely filled and the mortar has acquired a suitable consistency, the excess mortar is removed and the surface is adjusted by passing the ruler. Then, the depressions are filled with new mortar launches at the necessary points, and the battling operation is repeated until a flat and homogeneous surface is obtained. After all this process, the finish takes place, which we will see in the following topic.

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Surface finish

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The surface finish can be given in several ways and can be obtained by performing the following procedures:

• Bottled: Just follow the steps described above in the previous topic.
• Performed: perform the smoothing of the ribbed surface through the passage of the cutter.
• Suede: perform the smoothing of the surface performed with the appropriate sponge or squeegee.
• Scraping: finish the ribbed surface by means of a toothed tool.
• Washed: finish the ribbed surface on prepared mortar with appropriate aggregate, by washing with a water jet.
• Splattered: perform the finishing on the coating base or on the plunger by casting a fluid mortar, through a square mesh sieve with an opening of approximately 4.8 mm or appropriate equipment.
• Travertine imitation: finish the newly performed surface by drilling the same finishing mortar with a more fluid consistency. Wait for the ideal moment to smooth the surface with a trowel or steel cutter, preserving part of the grooves or cavities resulting from the release of the fluid mortar, in order to give the appearance of the travertine marble.

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Conclusion

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Now that you know what the NBR 7200 talks about, there are no more excuses for not following the guidelines established by it, in order to guarantee a quality work! Like NBR 7200, consulting the other technical standards is essential to carry out the procedures in the best way. Therefore, always pay attention to the recommendations determined by the technical standards to obtain excellent results! Keep visiting our blog to follow the new articles that we will publish about the NBR's! And don't forget: count on Blok for any challenge!