wallsBuilding with blocks is a technique that is more than secular. The Egyptians, Greeks, and Romans preceded us. Today, we no longer use large blocks of natural stone to build the internal load-bearing walls, but large bricks such as hollow clay brick, concrete blocks, cellular concrete, silico-calcareous …

With the appearance of hollow walls, the use of hollow blocks for the construction of interior walls and load-bearing walls has become widespread. If previously only solid concrete blocks were used, hollow terracotta blocks or concrete blocks, Argex blocks, blocks made of cellular concrete or silica sand have now taken their place. Block construction is largely justified by its low cost, the speed of execution, flexibility and insulating power. Overview.

The hollow wall

  • Until about the middle of the last century, only solid walls were built. The south of Belgium used mainly natural stone (because it was available in the region and cheap) while the north of the country built mainly brick (because the clay was there enough). This type of solid wall was finally expensive because it required a large workforce and a lot of materials. Moisture problems appeared frequently and the whole thing was particularly inert. Inert in the sense that the mass and composition of the walls were such that they had a large heat capacity: a house with such walls is difficult to heat in winter (disadvantage) but keeps a pleasant coolness in summer longer (advantage ).
  • The solution to these problems came from the invention of the hollow wall. An inner wall, the supporting part of the wall, is built with hollow concrete blocks or hollow terracotta blocks ). Better market and also faster to implement. Along with this supporting wall and connected to him for the stability of the whole, is placed the exterior wall, built in brick format classic. Between the two, avoid. Moisture that passes through the exterior wall can be evacuated by open vertical joints in the bottom of the wall.

This method of construction reduces the inertia of the wall. The hollow blocks in concrete or elbow type inevitably use less material and therefore have a lower mass. And this method of construction also increases heat losses.

  • The first oil crisis quickly revealed the importance of losing these precious calories. Since then, the insulation must prevent them from escaping through the walls. The hollow of the wall was presented and always presents itself as the ideal place where to install this insulation. Placed against the inner wall, the insulating material functions as an important barrier to heat loss. In addition, so laid, it is safe from moisture.

Concrete blocks

# The concrete blocks are made of cement, sand, and gravel. By its composition, the concrete is hollow but it is possible to remedy (partially) by incorporating some additives or by “vibrating” to prevent the formation of air bubbles.

# Solid concrete blocks can withstand heavy loads. This is why they are used extensively for foundations and basements (underground and load-bearing masonry). They are obviously also very heavy, which is a disadvantage not only in terms of their transport but also for their implementation on the site.

# Masonry above ground is usually made of hollow blocks: they always have a high lift but are lighter and therefore easier to masonry.

There are huge differences in quality and price in hollow concrete blocks due to the diversity of locations and manufacturing conditions. So always demand the Benor label as a guarantee of quality.

The Benor label guarantees that the product meets the Belgian standard (NBN).

The problem does not arise for other types of blocks, manufactured by large firms and under controlled production conditions. They not only have the Benor label but often also a technical approval.

# Concrete is a heterogeneous product: it has open pores and is therefore not waterproof, neither with water nor with the wind. A defect that can still be reinforced by cracks or cracks in mortar joints. Because of its high weight, the concrete block offers good acoustic insulation.

Concrete blocks of expanded clay balls

# Generally called Argex blocks … which is actually a brand name. The mixture of which they are made replaces the round gravel or the pebble by balls of expanded clay. As these expanded clay balls are much lighter, so are the blocks and are therefore much easier to handle.

# Expanded clay balls also contain a lot of trapped air that gives these blocks better insulating power. By cons, their lower weight plays against the sound insulation. They also have lower lift than hollow concrete blocks.

Terracotta hollow blocks

# These are large perforated bricks, much larger than the traditional facade bricks that everyone knows (for example 29cm long, 9, 14 or 19cm high and 9, 14 or 19cm wide).

# Compared to concrete blocks, they are lighter and therefore easier to implement for the mason. They are mainly used for the construction of the inner load-bearing walls, but their lift is lower than that of concrete hollow blocks and from a mechanical point of view, they are also more fragile.

# The hollow clay bricks are more efficient than the bricks full in terms of thermal insulation. But because of their lower mass, they are a less acoustically insulating agent than solid concrete blocks. However, there are, as always, exceptions: Terca offers the Porotherm brick, which provides better sound insulation than the others.

Note: there have also been for some time, hollow clay bricksĀ  that can be glued instead of being masonry. The technique of assembling the blocks with a thin layer of special glue is relatively recent. The adhesive layer must be uniform and the placement of the blocks must be precise. This gluing, however, requires special tools and experienced distributors. This method improves the airtightness of the wall.

Cellular concrete blocks

# These blocks are made of a mixture of sand, lime, air, water, and cement. The blocks of cellular concrete are light and white in color.

# By the very fact of their manufacturing method, these blocks contain a lot of small air bubbles which give them a better insulating power. Used in 24 and 30 cm thickness, they make it unnecessary to install additional insulation to meet the standards of PEB (energy performance of buildings).

The blocks are large but remain very light because of their composition. Which makes their use very easy and less tiring.

# Because of their production mode (large blocks cut), they are easy to cut to measure and have smooth surfaces. These blocks are usually not mortared, but with special glue cement. They are windproof and the bonding technique virtually excludes the presence of air leaks.

# When working with cellular concrete blocks, the lintels, slabs and roof panels must be of the same material to avoid thermal bridging.

# Cellular concrete is a soft material in which it is easy to dig ducts to embed pipes for electricity, sanitary or heating. Holes can be drilled just as easily with a simple drill. It is also a material in which it is easy to nail, which can be interesting when you want to affix some wall or ceiling coverings.

# The flatness of the walls allows the installation of an external plaster, with or without installation of an additional insulation. This obviously saves the costly work of masonry an exterior wall, but this finish is not allowed everywhere (urban planning requirements, but especially subdivision requirements) and everyone is not amateur. In other words, these blocks can do without a hollow and an outside wall.

Silicone blocks

  • This material is made of sand, lime, and water, without additives. Silicone blocks are among the building materials that have high dimensional accuracy. This criterion is particularly controlled in the context of the Benor approval. Silicone blocks are white.
  • The high compressive strength of silicate makes these blocks an ideal material for load-bearing walls. They can even be used for cellar walls or walls that have to withstand heavy loads.
  • Silicone blocks can be glued. Combined with an insulation placed on the slide (an insulating hollow), they give good thermal insulation. Thanks to their good sealing and mass, they also provide good sound insulation. Finally offering a great thermal inertia, they make it possible to avoid the strong variations of temperature.

How to choose?

All these materials have already proven their qualities in practice. All have their advantages and disadvantages. The main aspects that must be taken into consideration are their specific advantages (solidity, insulation coefficient, etc.), the price, the speed of implementation, the urbanistic prescriptions and the contractor’s experience of the material. selected. An entrepreneur who is used to working with concrete blocks and less with blocks made of silicate or cellular concrete will tend to inflate a little his price offer if he has to work with the latter.

All the blocks are manufactured industrially and this manufacturing process requires energy. For some, this criterion can be important.

Finally, the house must meet certain requirements in terms of energy consumption (EPB in Flanders and new regulation planned for late 2007 in Wallonia and the Brussels region). The choice will have to be decided in agreement with the architect and according to the relative calculations of the future consumption of the house. This last criterion is even more important because when you have paid the house, you will have to start paying the energy bills. The more you reduce it, the more you will gain in the long run.

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