Rules for laying floor slabs on a structure

Laying the floor slabs is one of the most important phases in building construction. Your floors are built on these slabs, which give everything above stability and support. For the structure to be safe and last a long time, proper installation is crucial.

It’s crucial to adequately prepare the location before starting. This entails making sure the ground is level and removing any debris. For the floor slabs to sit properly and support the weight of the building without wobbling or cracking, a level, sturdy base is essential.

The slabs’ proper placement needs to then be planned. This entails precisely aligning the slabs and taking accurate measurements. Later on, even minor misalignments can lead to serious problems that compromise the structural integrity of the entire system. Achieving the required precision can be aided by the use of markers and guides.

The slabs must be firmly supported during installation after they are in place. Scaffolding or temporary supports could be used to hold the slabs in place until they solidify completely. By taking this step, you can be sure that the slabs will settle into their final position with stability and proper alignment.

Lastly, it’s critical that the slabs cure properly. The concrete can reach its maximum strength and durability thanks to this process. Usually, it entails providing the slabs with a certain amount of moisture and protection from high temperatures. Rushing this process can result in floor failures and weak spots.

By adhering to these guidelines when installing floor slabs, you can guarantee a solid, sturdy base for your building. Although it may seem like a laborious process, paying close attention to detail now will result in a longer-lasting, safer structure.

Types of reinforced concrete floor slabs

Several varieties of standard-sized reinforced concrete slabs are produced by manufacturers for use in floor arrangements.

• tent-shaped (ribs are located along the perimeter);
• with longitudinal ribs;
• flat (solid, without voids);
• hollow core (with longitudinal voids of round or oval shape).

The slabs with flat and hollow cores are the most commonly used. In this instance, flat (PT), which range in thickness from 80 to 120 mm, serve as extra components. They are used to cover storage rooms, restrooms, small hallways, etc. because they are shorter and narrower than hollow-core ones.

The most widely used hollow-core reinforced concrete slabs are the continuous molding (CMS) and circular hollow-core (CH) varieties. The slab’s weight is decreased and its ability to insulate against heat and sound is increased when voids are present.

For many years, PC boards have been utilized in construction projects. Standard mass-produced goods are 220 mm thick and range in length from 2700 mm to 9000 mm in 300 mm steps. The width is 1200, 1300, 1400, and 1800 mm.

Standard round-hollow slabs are used in individual construction, but it’s crucial to consider their dimensions and installation features during the building design phase because these will determine how far the slab will rest from the walls. The cost of producing non-standard length custom PC slabs will rise dramatically because the manufacturer will need to create special formwork.

While the manufacturing technology allows for continuous molded reinforced concrete of any length, PB slabs are the same width and thickness as PC. This enables the ordering of structures that are the precise length needed for construction in accordance with a given project. The lack of thoroughly developed regulatory documentation and the relative lack of experience with PB slabs are among their drawbacks.

Basic principles for laying hollow-core slabs

The fundamentals of laying floor slabs:

1. Elements of precast reinforced concrete floors must rest on wall or foundation structures with their short sides.
2. Before installation, voids at the ends must be sealed with special concrete inserts or lightweight concrete M200 – this will make the slabs stronger in the nodes of clamping by the wall.
3. Building mortar must be applied to the supports. Grade – from M100 and above, layer thickness – from 20 mm.
4. The slab must not be turned over. In order for the structure to withstand high loads, reinforced reinforcement is provided in the lower plane of the slab to resist stretching. An incorrectly installed slab may break during operation. The lower surface of the reinforced concrete product (the future ceiling of the room) is smooth, the upper surface is rough, uneven.
5. Installation work is carried out by three to four people, special lifting equipment is used. One person attaches the slab to the crane hook using a four-leg sling, two others are engaged in laying the slab in its designated place and unhooking the sling. If work is carried out outside the crane operator’s viewing area, an additional person is required to give commands to the crane operator.
6. The slabs are laid as tightly as possible. If the length of the room is not a multiple of the width of the elements, the remaining gap between the floor slabs during installation is sealed with monolithic concrete, having previously installed the formwork.
7. At the final stage of installation, reinforced concrete slabs are anchored to the walls and to each other to ensure the rigidity of the entire structure. The installation step of anchors on the walls is 2-3 meters. The floor of the entire floor must be a rigid solid disk so that the building is stable and does not collapse for as long as possible under high seismic activity.

Laying floor slabs on the foundation: installation rules

In the construction of buildings composed of brick, foam concrete, or aerated concrete blocks, the basement or foundation walls are typically where floor slabs are placed.

In cases where the plinth or base of the foundation is composed of foundation blocks rather than a monolith, the structure must be reinforced with a monolithic reinforced concrete belt. Consequently:

• the load from the ceiling will be distributed evenly;
• the strip foundation will have increased bending strength;
• the edge of the foundation will be leveled, which will allow the slabs to be positioned correctly;
• the rigidity of the building and its resistance to small ground movements will increase.

Because foundation blocks are not reinforced, they become less strong when subjected to bending loads. These loads result from laying floor slabs on block structures because the support only spans a small portion of the inner side of the block rather than the full width.

A monolithic concrete belt’s reinforcement can reduce the chance that the basement or foundation walls will collapse. Regulations state that it must be 200 mm thick and that concrete B20 was used in its manufacture. Four rods that are positioned along the wall and joined to one another both horizontally and vertically by steel rods make up the spatial reinforcement frame.

Preparation for installation

The minimum support value as per the guidelines for installing floor slabs on the basement and foundation is:

1. for a concrete base – 60 mm;
2. for a brick base:

• 70 mm for slabs up to 4000 mm long;
• 90 mm for slabs over 4000 mm long.

In every situation, raising the support value to 120 mm is advised in order to strengthen the structure. With this method, you can supply the appropriate buffer in the event that the slabs are installed slightly off-center.

Floor slabs should only rest on their short sides when placed on a plinth or foundation. The reinforced concrete slab will not function properly under loads if intermediate supports are used, and the structure will collapse at the additional support point.

In order to avoid condensation, excessive heat loss from the building, and increased heating expenses during the winter, the ends of the slabs need to be insulated. Extruded polystyrene foam does not require waterproofing, but mineral wool and foam plastic need to be wrapped in polyethylene film to keep out moisture.

It is imperative to locate the lifting equipment before beginning installation work because it is not possible to let the soil shift under its own weight and press against the basement or foundation wall without running the risk of damaging it. The actual installation is done in compliance with the broad guidelines mentioned above.

Laying reinforced concrete floors on walls

The characteristics of the material used to construct the wall structures are taken into consideration when choosing the technology for installing floor slabs on walls.

Walls made of aerated concrete

Along the building’s contour, an aerated concrete block reinforced belt must be constructed. Both internal walls that are supported by a foundation base and external load-bearing walls are constructed using a monolithic structure.

• B15 concrete or a higher strength class is used for a reinforced monolithic belt;
• The width of the belt must correspond to the width of the wall, but for walls wider than 500 mm, it is permissible to reduce this indicator of the reinforced belt by 100-150 mm;
• The slabs and the belt are additionally connected by welding embedded parts.

When placing slabs on aerated concrete blocks, the support depth needs to meet the following requirements:

• from 40 mm when supporting along the contour:
• from 50 mm for reinforced concrete products up to 4200 mm long when supporting on two sides;
• from 70 mm for reinforced concrete products longer than 4200 mm when supporting on two sides.

Brick walls

Brick walls are built to the intended ceiling height, using their entire thickness. Then, because the masonry is only done from the outside of the structure, a niche is created where the floor slab’s edge will be installed.

Standards state that a support depth of no less than 90 mm is acceptable. However, in order to create a thermal insulation gap, a niche 130 mm deep must be formed and a support depth of 120 mm (half a brick) must be provided; otherwise, the floor will act as a cold bridge.

Use the same mortar that was used to lay bricks to lay floor slabs on a brick wall.

Common mistakes

The foundation of the building’s dependability is the proper placement of the floor slabs. Typical errors made when installing include:

1. Using damaged slabs. Thin shallow cracks can be repaired with mortar and the slab can be used on a low-load section of the floor. If the crack is through, such a product is used for the manufacture of short sections or rejected. Most often, slabs are damaged due to violation of transportation rules.
2. The support depth is below the established minimum. In such a situation, the load from the slab falls on the edge of the brickwork or armored belt, which provokes its slow destruction.
3. Extremely large support depth. In such a situation, the slab is pinched inside the wall and cannot work properly under loads. As a result, it begins to destroy the masonry. In addition, the end of the slab is close to the outer side of the wall, which increases heat loss in the building.
4. Incorrect anchoring or its absence. If the slabs that make up the prefabricated floor are not connected to each other and to the walls, or the anchoring is done incorrectly, the rigidity of the structure is insufficient and there is a risk of movement of the slabs and walls, especially in seismic conditions. This threatens the stability and integrity of the building.

To ensure stability and longevity when laying floor slabs on a structure, precise planning and execution are necessary. Prior to precisely placing and aligning the slabs, you must first prepare a firm and level foundation. Using beams or columns to distribute weight evenly is essential for proper support. Incorporating expansion joints can also stop temperature changes from causing cracks. Last but not least, complete curing of the concrete increases its strength and durability, which is necessary for an effective installation.

Conclusion

The choice of floor panels should be made during the building’s design phase to prevent needless issues with caulking the gaps between the slabs. Hollow-core slabs cannot be stacked on top of one another without wooden spacers, so it’s crucial to abide by the regulations regarding the storage and transportation of reinforced concrete products.

For any structure to be strong and stable, floor slabs must be laid correctly. Observing the fundamental laws and regulations aids in avoiding common problems such as uneven surfaces, cracking, and long-term damage. You can achieve a long-lasting and dependable floor by paying close attention to every step, from foundation preparation to concrete curing.

Making sure the foundation is level and ready is essential. This helps distribute loads evenly and gives the slabs a sturdy base. To further improve the structural integrity of the slabs and lower the likelihood of cracking and other types of deterioration over time, appropriate reinforcement with steel bars or mesh is essential.

Maintaining the proper distance between slabs during installation is crucial to allowing for expansion and contraction. This helps to adapt to variations in temperature and keeps the slabs from squeezing against one another, which could cause damage. Additionally, a level surface is guaranteed and uneven settling is prevented by making sure the slabs are properly aligned and supported during installation.

For maximum strength and durability, proper curing is necessary after the slabs are laid. In order to ensure proper hardening, the concrete must be kept damp for a predetermined amount of time. If this step is skipped, the structure may become weaker and more vulnerable to damage.

You can make sure that your floor slabs are laid correctly and give your building a sturdy, long-lasting foundation by adhering to these guidelines. The overall quality and longevity of the final product are greatly impacted by the level of attention to detail that is paid at every stage of the process.

Video on the topic

Even laying of floor slabs without reinforcement.

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HOW TO CORRECTLY LAY FLOOR SLABS