The subtleties of building a plinth from blocks: concrete, expanded clay concrete, aerated concrete

The portion of the structure that sits between the foundation and the ground floor, known as the plinth, is vital to the construction of a building. Its primary function is to shift the weight of the building to the foundation; it is the foundation’s extension. The plinth prolongs the life of the entire structure by acting as a barrier against moisture and outside influences. For this section of the building to be stable and long-lasting, the right materials must be chosen.

Aerated concrete blocks, expanded clay concrete, and concrete are the three most common materials used to construct plinths. Due to their distinct qualities, each of these materials can be used for a variety of projects. Because of their strength and longevity, concrete blocks are a great choice for high-load areas. Aerated concrete blocks are lightweight and simple to work with, but expanded clay concrete blocks have superior insulating qualities.

We will examine the intricacies of constructing a plinth with these various block kinds in this article. We’ll examine the strength, insulation, and ease of installation of each material. Furthermore, we’ll offer guidance on selecting the ideal block variety for your particular building requirements, guaranteeing that your plinth is not only sturdy but also economical and energy-efficient.

Material	Description	Advantages	Disadvantages
Concrete	Concrete blocks are dense and heavy, providing strong support for the structure above.	High strength and durability, excellent load-bearing capacity, fire-resistant.	Heavy and difficult to handle, requires skilled labor for installation.
Expanded Clay Concrete	These blocks are made by mixing clay aggregates with cement, creating lightweight and insulating blocks.	Lightweight, good thermal insulation, easy to work with.	Lower strength compared to traditional concrete, may require additional reinforcement for load-bearing walls.
Aerated Concrete	Aerated concrete blocks are manufactured with tiny air pockets, offering excellent insulation and reduced weight.	Good insulation, lightweight, easy to cut and shape.	Less load-bearing capacity, more prone to moisture absorption.

Are the products suitable for construction?

There is no prohibition in the regulatory documents against using concrete blocks to build a plinth. However, this does not imply that using them for all kinds of residential buildings is a good idea.

An enormous amount of calculations must be made during the crucial base construction phase, taking into account real values such as the strength of the building materials, the features of the structure, and the soil’s geological parameters.

When a house is being designed, the base material is selected after a technical and financial comparison of various options. The following variables will affect the choice: weather, soil properties, building height and area, wall material, foundation type, and transportation interchange.

The base requires extra protection from moisture and other elements related to its close proximity to the ground in wet and weak soils. A particular kind of block, such as expanded clay concrete (KB), aerated concrete (GB), or standard concrete (BB), can be chosen based on these indicators.

Since concrete blocks are laid with dressing, the size of the building in the plan also has a significant impact on the choice of blocks. It is important to consider that there are as few voids and non-multiple elements as possible when selecting their type. If not, building such a base will come at a very high cost.

When this is impossible?

Despite the fact that using concrete blocks is not prohibited by regulation. Sometimes they are not usable:

1. High groundwater level, since it will be impossible to provide the required degree of waterproofing due to the presence of interblock seams.
2. In buildings higher than 3 floors, due to low strength, compared to a monolithic base.
3. On construction sites where it is not possible to use lifting equipment.
4. For slab foundations, a monolithic base is more preferable here.
5. For columnar, pile foundations and a backfill. As a rule, the backfill is made of the same building material as the columns, or rubble, brick or reinforced concrete is used.

Certain developers build the base using foam concrete blocks. This isn’t always the case because, in damp soil, extremely porous foam concrete can function as a "capillary pump," sending moisture into the house’s walls.

As per the guidelines outlined in SNiP No. 2-22, which was released in 1981, the following materials cannot be used with a base that operates in a wet mode:

• semi-dry pressed clay blocks;
• hollow;
• silicate and cellular.

Types of material for the structure

The ground floor, which is made of concrete blocks, needs to fulfill:

1. reliability;
2. durability;
3. energy efficiency;
4. high level of strength;
5. resistance to precipitation;
6. high frost resistance;
7. be environmentally friendly;
8. have an attractive appearance.

Concrete blocks must thus fulfill each of these requirements. This means that the most popular modifications for building the base are expanded clay concrete (KB) and traditional concrete blocks, also known as foundation (FBS).

Concrete

The most popular contemporary building material for prefabricated basements and foundations is fiber-bearing styrene (FBS). The industry creates a range of sizes for both motor transport lifting equipment and manual laying.

Overall benefits of FBS for basement construction:

1. Does not require the preparation of a large volume of concrete mortar, as with a monolithic basement;
2. high frost resistance with F above 150, the ability to withstand temperature differences of tens of degrees;
3. high resistance to aggressive atmospheric influences.

The primary drawbacks of FBS for developers building a foundation are its high cost, which is 20–30% more than for building a monolithic one, and the need for motor lifting equipment for the laying of large elements.

As a result of the numerous seams that allow moisture to seep in and heat to escape, these walls need to have better thermal and hydro insulation.

When installing lifting equipment on a construction site is not feasible, FBS is utilized to build the plinth, which measures 200 by 200 by 400 mm (40 by 20 by 20 cm) and weighs up to 35 kg, allowing it to be manually laid.

FBS specifications: 200 x 200 x 400 mm

• density, 1550-2250 kg/m2;
• strength, M100-150/B7.5-B12.5;
• frost resistance not lower than F50;
• thermal conductivity not higher than 0.56 W/M°C.

Principal benefits of FBS: 200*200*400 mm for building a residential building’s basement:

• low installation costs, since there is no need to hire lifting equipment;
• high structural strength;
• high construction speed.

Developers believe that utilizing FBS: 200*200*400 mm has several drawbacks, including a high number of seams that lower the base’s thermal resistance and a higher need for masonry mortar.

Expanded clay concrete

A basement cannot be built using every expanded clay concrete block available. For instance, elements with voids and three-layer structures with an inner layer composed of thermal insulation material and an outer layer composed of concrete are included in this list.

It is permissible to construct a plinth out of hollow CB for small, low buildings that are constructed on dry soil, provided that the spaces are filled in with large, expanded clay concrete.

Standard 40x20x20 cm rectangular expanded clay concrete blocks are used for the plinth. With a joint thickness of 1-2 cm, this size is ideal because it generates less waste.

Expanded clay concrete block specifications for single-story homes up to three stories:

• Permissible strength – from 50 to 100 kg / cm 2 ;
• weight of 1 m 3 of the plinth from 0.8 to 0.6 t;
• weight of 1 m 2 of the plinth – from 700 to 800 kg;
• frost resistance from 50 to 150 cycles.

The main benefit of KB is the wall material’s light weight, which enables:

• to significantly reduce the load on the foundation of the house;
• reduce labor costs;
• increase the speed of construction.

Expanded clay concrete blocks offer the following key benefits when building a building’s base:

1. High heat and sound insulation characteristics.
2. Low cost compared to traditional FBS.
3. Ecologically friendly material.
4. Combines well with any building material.
5. Easy installation, processing and delivery.

Experts believe that expanded clay concrete blocks have poorer strength characteristics than traditional FBS, an unsatisfactory gray color appearance, and poor geometry that needs extra finishing.

Additionally, their vapor permeability is lower. Extra insulation is necessary for CBs thinner than 40 cm, particularly where curved elements converge because cold bridges can form there.

Aerated concrete

When building a basement, aerated concrete blocks (AB) are only utilized if the surrounding soil is not deemed weakly bearing. Furthermore, cold climate areas are not suitable for using aerated concrete.

Base requirements for blocks made of aerated concrete:

1. Height above 0.8 m.
2. Waterproofing walls.
3. Thermal insulation of walls.
4. The 1st row of masonry occurs on mortar.
5. GB is moistened with water when laying.
6. Minimum thickness – 400 mm.
7. Acceptable modification: D600, class B3.5.

Gas silicate has several benefits when used to make plinths, including being inexpensive, non-flammable, and light in weight.

The drawbacks are low strength, requiring more reinforcement, and high hygroscopicity, which needs to be decreased with more waterproofing.

Building requirements

The basement walls need to be able to withstand horizontal shifts caused by the pressure of the surrounding soil because a portion of them will be underground. As a result, the foundation is constructed with a reinforcing cage band surrounding a cushion of monolithic concrete.

Living rooms cannot be located on a ground floor if the ceiling is higher than two meters above the floor. If not, a basement of that kind would be regarded as a ground floor. The soil on the whole exterior face of such walls will also exert pressure on them.

As a result, extra reinforcement will be needed to build such walls using concrete blocks in increments of 40 cm vertically and horizontally, and the reinforcement frame will need to be attached to the foundation pad.

You have to adhere to the requirements for corner and joint reinforcement when installing walls. By building partitions, which will help distribute the loads on the basement walls, the structure can be strengthened generally.

The following are the main prerequisites for building a concrete block plinth:

1. The height of the plinth depends on the location of the premises, for technical rooms – from 1.8 to 2.2 m, for residential from 2.5 – 3 m with a reserve for multi-layer flooring and finishing work.
2. The thickness of the walls depends on the groundwater level. If they are not close to the foundation, the lower wall can protrude 10 cm from the outline of the building, and the thickness of the walls is up to 2.5m maybe 40cm.
3. When the base is located below the groundwater level, the base slab is reinforced with reinforcement. Moreover, it should be at least 20 cm thick and extend beyond the frame of the house by 40 cm.
4. The walls of the plinth must comply with the requirements of SNiP No. 2.09.03, published 1985, for retaining walls and basement structures.
5. When laying small-sized concrete blocks, for example, expanded clay concrete, the walls are reinforced with longitudinal reinforcement and horizontal belts on top of the masonry.
6. Prefabricated FBS must be made of concrete M150 and higher.
7. In basement rooms with a length of more than 25 m, expansion joints must be provided.

Necessary consumables and tools for construction

This type of wall material works great for building a basement. It has enough stability, is fairly simple to install, and can stop a sizable amount of soil masses from moving.

First, the developer needs to get a set of tools and consumables ready so that the masonry can be completed quickly and to a high standard. Whether you use aerated concrete, expanded clay, or FBS concrete blocks will determine which list you get.

The primary equipment and supplies needed to lay a concrete block plinth are:

1. Masonry mix.
2. Reinforcement and reinforcing mesh.
3. Protective materials: geotextiles, waterproofing films and mastic.
4. Concrete mixer with a capacity of 0.25 m3 .
5. Containers for transferring mortar.
6. Various shovels, including for collecting mortar in buckets.
7. Various trowels, spatula and notched trowel.
8. Rubber mallet.
9. Cord for marking the contour, ruler, laser level, level, square and tape measure and marker.
10. Compacting ram.
11. Lifting slings for blocks.
12. Angle grinder.
13. Electric drill
14. Hacksaw and metal shears.
15. For aerated concrete: carriage, chaser, float and rake-bucket.

The type of masonry mortar required for FBS will depend on the kind of concrete block being used; for FBS, this is M400 cement, sand, and clean water in a 1:4 ratio, with additional water added based on the solution’s consistency.

You can use a specific dry glue that has been diluted with water in accordance with the manufacturer’s recipe to create seams as small as 2-3 mm for aerated concrete blocks and expanded clay blocks.

Use frost-resistant tile adhesive with reinforcement technology for outdoor foam block work.

Concrete, expanded clay concrete, or aerated concrete are just a few of the materials you must carefully consider when building a plinth out of blocks. The choice of block type is essential to the stability and functionality of the foundation because each type has distinct qualities that impact weight, durability, and insulation. Aerated concrete blocks are lightweight and simple to work with, expanded clay blocks offer superior thermal insulation, and concrete blocks offer strength and stability. Recognizing these subtleties will help guarantee that the plinth not only properly supports the structure but also offers the longevity and insulation needed for optimal performance.

Step-by-step instructions for construction

The foundation of the house is the primary component of the wall structure, and the flawless execution of this component is largely responsible for the longevity and dependability of the entire house. Depending on the kind of blocks used—ordinary concrete, foam concrete, or expanded clay concrete—the base construction technique will vary.

From concrete stones

When it comes to strip foundation bases, this is the most dependable material. The thickness of the reinforced concrete is chosen based on the type of wall: 30 cm is sufficient for wood, 40 cm for blocks, and at least 60 cm for heavy brick.

Detailed instructions for building an FBS base on a strip foundation:

1. On the leveled strip foundation, waterproofing is carried out with roll materials.
2. Large structures are laid using a truck crane; the laying is done using a standard cement-sand mortar.
3. Block laying starts from the corner.
4. The first row is laid on cement mortar, the layer thickness is up to 1.5 cm, in order to create interblock vertical joints in the future.
5. The vertical joints are also filled with mortar, a reinforced adhesion is obtained using special grooves.
6. A mooring cord is pulled between the laid reinforced concrete products.
7. The masonry is carried out using standard technology with the lower and upper elements being bandaged in relation to each other.
8. Each horizontal joint is waterproofed, if the height is 10 elements, then ten waterproofing joints will be needed.
9. Deviations in masonry should not exceed the indicator: 1.5 cm per 1000 cm of masonry.
10. After the construction of the basement, a reinforced concrete belt is made to strengthen the structure.
11. After the construction of the basement, waterproofing is carried out using liquid rubber.
12. Thermal insulation is carried out.
13. The sinuses are filled with sand with tamping.
14. After thickening and the reinforced belt gaining the required strength, it is allowed to continue construction work.

Expanded clay concrete

Structural expanded clay concrete blocks with maximum strength indicators are required for basements of homes up to three stories, while structural and heat-insulating products—albeit with lower strength indicators—are adequate for low-rise structures.

Detailed instructions for building a basement on a strip foundation using expanded clay concrete blocks:

1. Laying begins on the leveled surface of the strip foundation.
2. Apply adhesive bitumen waterproofing.
3. On top of the insulation, perform final markings under the walls.
4. The marking cord is pulled along the perimeter of the box, at the design level, above the 1st masonry row.
5. Bring the corners of the box into 4 rows with a run-out groove.
6. Installation of KB is carried out by analogy with brickwork of walls on CPR masonry mortar. This approach significantly reduces the cost of construction on expensive dry adhesive compositions.
7. The masonry is carried out end-to-end, while vertical joints and horizontal seams must be filled with special care.
8. Technological openings in the basement should be marked on the masonry scheme in advance, so that openings are left for them.
9. For laying in-house utility networks, openings and grooves are made in the basement walls.
10. Reinforcement of the expanded clay concrete blocks is carried out according to the scheme, at least every 4 rows, using a masonry construction mesh.
11. After the construction of expanded clay concrete blocks, an armored belt is made along the entire perimeter.
12. Next, a layer of waterproofing and thermal insulation is arranged on the outside of the wall.
13. After the basement structure has completely hardened, the free sinuses are filled with sand, followed by tamping.

The expanded clay concrete’s fragility must be taken into consideration by the developer, so the components are compacted using a rubber mallet. For concrete, expanded clay is ground with a special cutting wheel to prevent crumbling around the edges.

Possible errors and difficulties in the process

The foundational device is an important part of the construction process; the quality and completeness of the technological map determines how long the house will function without problems. Only after the construction project has been developed, approved, and the materials have been purchased in accordance with the design specifications, can work begin.

In addition, the contractor needs to have a developed technological map for building the house’s basement and the necessary permits to perform such work.

Most of the time, mistakes made when building a base out of concrete blocks are lethal and can only be fixed by extreme difficulty and expensive means.

When building a plinth out of concrete blocks, workers are permitted to make basic errors:

1. Incorrect foundation type selected. Building elements, especially those made of aerated concrete, are not the most resistant to bending. In the case when the foundation on which the base will rest is not rigid and reliable enough, contains significant indentations in geometry, does not correspond to the type of soil and the relief of the territory on the construction site, then the masonry in some places can bend and crack.
2. Violation during laying of the 1st row of blocks. It ensures the geometry of the entire masonry, if during its construction significant deviations in height are allowed or diagonals are shifted, these errors can no longer be corrected on subsequent rows, on the contrary, they will only increase. The first row is allowed to be laid on the cement-sand mortar with a layer of up to 20 mm, but if the foundation has a difference in the horizon of up to 30 mm, the cement-sand mortar will not be able to level it – you will have to level the foundation and only then start laying.
3. Violations in waterproofing of the 1st row, there is no bitumen waterproofing between the wall and the foundation.
4. The masonry mortar was chosen incorrectly, especially for aerated concrete, or cheap low-quality glue was purchased, which creates large heat losses through the wall structures of the base.
5. Errors were made when bandaging the blocks, as a result, the masonry is not able to withstand the design bending and shearing forces. Russian regulatory requirements for dressing – at least 40% of the height of the block. For example, for 250 mm wall elements, the overlap must be at least 100 mm. and according to EU requirements – at least 125 mm. it is also prohibited to use elements shorter than 50 mm for the construction of the base.
6. Incorrect connection of load-bearing walls and partitions – rigid connection is made with blocks or pieces of reinforcement driven into the walls. Cracks will definitely appear in such areas.
7. Lack of reinforcement of every fourth row, especially for gas blocks.
8. Lack of armored belt or breaks in it
9. Hydro-, heat protection of external walls is not performed.

Pros and cons of use

There are benefits and drawbacks to using concrete blocks for base masonry, but the latter won’t matter if the wall material was selected after weighing several options during the design feasibility study.

Concrete block advantages include:

1. High strength and long service life. Such elements are used for multi-storey construction, they have proven their high performance in practice.
2. High fire resistance – they are used in the construction of fire-resistant walls.
3. High frost resistance. They have frost resistance rates of at least F 50, while they withstand temperature changes well, which is especially important when most of the basement walls are in the ground.
4. Low construction costs due to cheap raw materials, low labor costs and the use of third-party equipment.
5. Concrete blocks (except aerated concrete) have high moisture resistance rates, with water absorption of no more than 6%.
6. High sound insulation rates up to 30 dB.
7. Ensure high construction rates.
8. Environmentally safe materials.

Traditional concrete blocks present the greatest number of drawbacks. These include their high weight, which necessitates reinforcing the foundation, and low thermal resistance, which calls for extra thermal insulation of external structures.

Average prices for different types

Masonry costs are determined by a number of variables, including the type of mortar used, the reinforcement pattern, the size, volume, and height of the wall, as well as the team’s composition. Simultaneously, a general trend appears: the cost of masonry decreases with increasing block size.

Typical costs for masonry plinths vary based on the kind of concrete blocks used:

• FBS: 20x20x40 – 2900 rubles / m 3 ;
• aerated concrete – 1500 rubles / m 3 ;
• expanded clay concrete – 1900 rubles./m 3 .

Because fewer orders for construction work are placed in the region overall during the colder months, the cost of these kinds of work decreases, but their quality also decreases.

The average cost of one piece or one cubic meter of concrete blocks, based on size and source material:

• FBS EnergoProm, 9 * 5 * 6 – 1256 rubles.
• FBS Vyazma, 6 * 3 * 6 – 1174 rubles.
• FL Tver, 20 * 8 * 3 5 – 176 rubles.
• FBS Vyazma, 24 * 4 * 3 – 1491 rubles.
• FBS Vladimir, 12 * 4 * 3 – 733 rubles.
• KSL, solid wall concrete, 39 * 150 * F75 * 2000 b, 390 * 190 * 188 mm, 150 kg / cm 2 , D2000 – 63 rubles.
• KSL, solid concrete, 39*150*F75*1800 390*160*188mm, M150kg/cm2 D1800kg/m3 — 58 rubles.
• KSR-PZ, solid concrete, 39*100*F75*2050 — 49 rubles.
• SKM 1 Besser, solid concrete, 390-190-190mm, M100kg/cm2, D2100kg/m3 — 59 rubles.
• Koldiz KSR-PR, solid concrete, 390-190-188mm, M100kg/cm2 — 72 rubles.
• Besser SKK 1 solid expanded clay concrete, 390-190-190mm, M100kg/cm2 D1800 kg/m3 — 89 rubles.
• Cubi Block aerated concrete, 625-400-250 mm B3.5 D600 kg/m3 — 7,900 rubles./m3 .
• Bonolit aerated concrete, 600-400-200 mm B3.5 D500 kg/m3 — 8,200 rubles./m3

Whether using aerated concrete, expanded clay concrete, or concrete, building a plinth from blocks requires careful planning and execution to ensure a sturdy and long-lasting foundation. Every material has distinct benefits and drawbacks, so it’s critical to select the one that best meets the demands of your particular project. Concrete blocks are perfect for large structures because of their exceptional strength and durability. Because expanded clay concrete blocks have better insulation qualities, they are a good choice for spaces where thermal efficiency is important. Aerated concrete blocks offer excellent insulation, resistance to fire and vermin, and are lightweight and simple to work with.

It’s important to consider the quality of the blocks and the mortar used to bind them when building a plinth. Problems like settling and moisture infiltration can be avoided by properly preparing the ground and making sure there is enough drainage. Furthermore, the strength and stability of the plinth can be greatly increased by adding steel bars or other reinforcement to the structure, particularly in regions where soil movement or seismic activity is likely to occur.

Lastly, to guarantee that your project is up to par, always abide by local building codes and regulations. It can be helpful to consult with experts or seek their advice, particularly for complex projects. You can make a plinth that not only provides efficient support for your structure but also endures for many years by being aware of the subtle differences between each material and adhering to recommended practices.

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