For the application of the plaster inside, some important steps are necessary in order to obtain a durable result, without cracks, efficiently and with the promoted properties. Regardless of whether it is applied manually or mechanically, the steps remain the same and must be followed exactly so as not to wake up with crooked or cracked walls shortly after the end of the project.
Depending on the type of interior wall, the formula used for plaster may be different. The binder dosage is generally low, the ratio of water / cement being higher and smaller grades of mortar being used. It is mentioned that the type of surface on which it is applied has an importance in terms of choosing the mortar necessary for a resistant work. Here is some information regarding the work stages and their specific details.
The choice of mortar
In the case of indoor application, the type of wall is, however, important, it determines the class of mortar. The thicker or harder the wall is, the lower the mortar grade will be. For an interior wall of brick and concrete, the recommended class is CS IV, and for simple concrete the ideal class will be CS III. For the interior walls of BCA, the CS II mortar class will be recommended.
When using a mixture that includes sand, its thickness will be of some importance. Depending on the layer applied, you will choose a sand of larger or smaller dimensions. For the first layer the size will be between 4 and 8 mm, and for the primer it will be 2 – 4 mm.
How to get a thin and straight wall
In most cases, it is recommended to apply plaster layers in two installments, the first being primer and the second plaster. The base layer and the thickest is the primer, it giving the constant surface of the wall, being able to be applied both manually and mechanically, using the trowel, the trowel or the special device. It will keep a harder and rougher surface so that the plaster, applied over the dry primer, adheres better. The action will always be done from top to bottom.
The first step – cleaning the substrate and preparing it
The action from which the other steps start and, perhaps, the most important, is the cleaning of the surface on which the plaster will be placed, later. The wall should be stable and free of dust, cement or traces of grease or oil. When it comes to a fast absorbing surface, a primer will be applied, the working temperature being between 5 and 30 degrees Celsius.
The wall is bridged using W10 or W6 profiles, 24 hours before applying the plaster. The distance between the profiles should not be greater than the long dimension of the trapezoidal or H-type straightener used for leveling the mortar. For the exterior corners, some corners designed for plaster will be useful.
Step 2 – preparation of working materials
In case of manual preparation, a clean tub will be used in which the specified amount of water is poured from the product packaging and the desired plaster. After a few seconds or the specified waiting time, mix until a unit paste is obtained.
When the consistency is much too viscous, water can be added to make the fluidity different, but more dust will never be added to the mixture, as it can make homogenization difficult by speeding up the setting time.
For the mechanized preparation, you will simply start the plastering machine , carefully adjusting the water flow to suit the material, and then add it to obtain a homogeneous paste of the desired consistency.
Step 3 – application
It can take place mechanized, when the spray gun will be used and the application pressure will be adjusted, so that the user can control how thick the mortar layer will be, or manually, by using trowel, trowel, spatula or cancioc.
For a correct application, it is recommended to use clean tools, because oil stains and other impurities can affect the quality of the result.
The plaster will be used between the bridged profiles the day before, and if the machine is used, the instructions of the manufacturer and of the special construction materials will be followed.
When the mechanized technique is followed, it is preferable that the mixture does not stay in the hose for more than 30 minutes, as it can dry out and cause damage.
Step 4 – leveling
In order to obtain the flat surface, checks will be made with the poloboc and the straightener. First, the material will be leveled by using the straight H or trapezoid, in this way ensuring its spread over the entire surface. Following this step, the W6 and W10 profiles are removed and the free space will be filled with mortar.
Step 5 – Scraping
After about an hour has passed from the previous step, the entire surface will be carefully scraped using a trapezoidal straightener or a lamella brush.
The paste that remains to be scraped will be used, later, to fill existing bumps and gaps or discovered along the way.
Step 6 – Finishing
About 45 minutes from the previous step, the plaster will begin to harden and, while the outlet takes effect, the space will be smoothed with a utensil (drisca) provided with a sponge at the end, previously soaked with water.
After smoothing, a fine paste will be obtained which can be used, later, for finishing with the spatula or trowel. By using a larger tool it will be easier to control the condition and shape of a larger surface, ideally it should be flat.
In order to obtain a surface ready for painting, the smoothing and finishing can be repeated.
In order to dry, the plaster needs, on average, up to 96 hours, after which it will be checked and, if it is ready, it can be covered by a finishing plaster to have a superior quality, or it can be passed directly to the steps. specific for painting with washable material.
Depending on the type of materials used, the consistency of the plaster and the thickness of the layers, the waiting period may increase or decrease. Humidity, drafts or room temperature can also be important when it comes to drying times.