One of the fundamental steps for completing the structure of any type of property is the construction of the slab. You can choose either the traditional version, which is made on site, or choose the pre-molded slab, which has the advantage of being more economical and easier to be assembled at the construction site. These characteristics end up attracting many people who want to build, but also need to save money and want to have less headaches during the work.
But do you know what a precast slab is? Did you know that there are several types of slab? Do you know how much it costs and which one is the best option for your construction? To answer these and other questions, we decided to share this article full of important tips you need to know before starting this stage of your work.
In the same way as the conventional slab, the precast slab or prefabricated slab, as it is also known, is one of the elements that make up the structure of a building. The function of this structure is to distribute the weight of the roof over the beams and pillars of the building. For this, it is composed of concrete joists and slabs (slats) of concrete or ceramic, which are the blocks used to cover the structure.
Thus, the slab is used to cover, provide thermal and acoustic comfort to the environment, and can still be used for future additions, such as in the construction of attics, for example. However, the precast slab is different because it is produced through industrial processes, allowing its assembly to be easier and more economical, since it is composed of prefabricated elements.
Because of this practicality at the time of assembly, the precast slab has been increasingly used as a constructive solution by those who wish to build their home or office.
Image 1: The pre-molded slab lattice with Styrofoam is one of the most used in constructions.
Before choosing the ideal slab for your construction, it is also important to know the advantages and disadvantages of its use, so that you are aware of the characteristics of the products you are using in your work. Therefore, we have separated some of the pros and cons of using precast slabs.
Image 2: The prefabricated slab is much easier to be installed, requires less labor and speeds up the completion of this stage of your project.
If you’d like to know the characteristics and advantages of precast slabs, then it’s time to learn more about the different types of this structure. After all, you will have to choose one of them to use in your project. So, pay attention to the description of each of them listed below.
Precast lattice slab with tile
The lattice slab with tile is widely used in civil construction, as it can cover large spans, and can be used in the construction of your L-shaped house, for example. It is made up of joists, which are small beams, with a concrete base that supports a metal truss, which are covered with concrete or ceramic tiles. After the assembly of this step, the precast slab still needs to receive a concrete cover, which will unite this entire structure.
However, as not everything is flowers, you need to know that the material used in the assembly of this type of slab makes it difficult to drill holes and openings for the passage of pipes, for example, as well as requiring the application of roughcast or plaster to cover imperfections, as its material is not very resistant.
Image 3: The precast lattice slab with tile is an excellent option to cover wide spans.
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Image 4: However, don’t forget that it is necessary to add a concrete cover to join this structure.
The EPS lattice slab, also called Styrofoam lattice slab, differs from the previous type in that it uses Styrofoam plates instead of concrete or ceramic slabs. In addition, due to the use of these EPS boards, this type of slab also has a lighter structure, easy to assemble, which allows the installation of conduits and pipes for the passage of water and electrical materials.
It is worth remembering that the EPS lattice slab is indicated for those who want an environment with better acoustic and thermal insulation and, therefore, it is very suitable for buildings in urbanized areas or areas that suffer from temperature variations, such as in houses of field.
Image 5: Styrofoam slab is the best option for those who value thermal and acoustic comfort.
Image 6: In this image, you can see the view from inside the room that received the base structure of this type of slab.
Hollow core slab is widely used in large constructions, such as parking lots, hospitals, supermarkets and universities, since it has a high resistance to compression and uses a specific steel model for protection. In this way, it can support a great weight and can be applied in wide spans.
This is because the hollow core slab consists of hollow prestressed concrete panels with longitudinal alveoli, capable of reducing the weight of the pieces, which would be much greater in the traditional model, which could hinder the construction of these large works. The only problem with this slab is transportation. Due to the weight and size of the panels, it has to be transported to the installation site by cranes.
Image 7: Prestressed panels with longitudinal alveoli are giant structures. Therefore, they need to be installed with the help of cranes.
Image 8: In this image, you can see how these concrete panels are perfectly distributed in the space, a work carried out with the crane, which remains on the side of the building.
Despite the similar names, the lattice panel precast slab is different from the lattice slabs shown above. In this case, the reinforced concrete beams that support the metallic structure have a larger base, with larger and more resistant ribs, allowing this structure to support a much greater load. The panels formed with this structure are arranged side by side, forming their own specific shape for concreting.
Due to this constitution, this type of precast slab is very suitable for large projects, which have a large load and require a structure resistant to compression. Also, as the panels are finished well, they do not need plastering. Therefore, in this case, only one coat of varnish is needed to waterproof the slab and prevent corrosion of the concrete.
Image 9: These concrete beams draw attention because they have a wider base compared to the traditional beam.
Image 10: Furthermore, when placed side by side, these joists fill the entire space and therefore the lattice panel slab does not need tile.
Finally, you can opt for the pre-molded slab with “T” beam, which are more conventional. In the same way as the lattice slab with tile, they are composed of concrete joists and concrete or ceramic slabs. However, in this case, the joists are solid rails with a “T” cross section, used to fit the tiles.
And to connect all these components, it is necessary to use a layer of concrete, forming a layer over this structure. However, the disadvantage of this slab with “T” beam is that it does not support overloads that were not foreseen in the project, that is, it is not possible to make any adaptations at the time of assembly.
Despite this, this slab can be a great option for small projects for small buildings, since they do not have large spans or a large overload.
Image 11: The “T” beam is formed with cement and is distinguished by not leaving any exposed trusses.
Image 12: However, it also requires the use of tiles and the addition of the concrete cover.
Now you may be asking yourself: But how much does a precast slab cost?
First, you need to know that the precast slab is sold per square meter, and the value depends on the type and its constitution, that is, if it is made of Styrofoam or slab. In addition, the prices charged vary according to the city and state, so it is worth researching the price in your region. But, in general, we can tell you that the price of Styrofoam is cheaper than tiles, since it can be found for around R$24.00, while the second can be purchased for R$36.00.
But this will not be your only expense, as you will also need to invest in the iron mesh that will support the slab beams, in the size of 0.15cm X 0.15 cm, and which can be found on the market for around R$ 50.00. In addition, it will also be necessary to invest in machined concrete to join the slab structure, which can be found for around R$ 280.00 per m².
Of course, we are talking about materials that can be used in precast slabs with latticework or EPS. If you want to use hollow core slab, for example, the price will be different. As mentioned earlier, it all depends on the type of slab you want to adopt.
Remember that you will also have expenses with labor and with hiring an engineer to make a specific project for your work, calculating the exact measurements of the materials needed to build your slab.
To avoid paying more to build your slab, it’s worth following the tips below.