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Leca®BLOK - walls with high acoustic insulation

19 of July '22

From what and how to build? Leca®BLOK - the smart choice!
From the series "The most popular facade and wall materials - review 2022".

In residential construction, there are mostly two basic solutions. Single-family buildings and apartments in multi-family buildings. In both types of housing we need to ensure proper acoustic comfort. Practice shows that in single-family buildings the requirements are lower.

Doors to most rooms are often open, rooms are connected by an open cage and the actual insulation of the wall with the door comes down to the level of insulation of the door. In addition, interior doors are often intentionally leaky to facilitate air exchange in the rooms. Therefore, in single-family homes, acoustic comfort depends on how loudly we listen to music and how loudly the occupants of the house behave.

Leca®BLOK – ściany o wysokiej izolacyjności akustycznej

Leca®BLOK - walls with high acoustic insulation


In multi-family housing, effective sound insulation of walls between apartments is definitely more important. Noise generated in one apartment must be effectively stopped by the walls and ceilings between apartments. In the past, no one was concerned about acoustics. The first standard on acoustic requirements appeared in 1970. However, due to very limited access to measuring equipment, it was difficult to enforce compliance.

It was only under the introduction of the standard in 1999 that more active efforts began in the direction of building acoustics. Nowadays, the requirements are very strict. The current standards of 2015[1] and 2017. Developers are commissioning sound insulation tests of walls and ceilings before final inspections. Positive results from these tests provide peace of mind for the Developer, protecting him from potential complaints, but also peace of mind and comfort for the residents.

Of what and how to build?

The answer is simple. Use wisely elements proven in acoustic laboratories and on completed buildings. And how to build - tightly.

It is worth extending these principles. Wise selection of the right elements for the construction of a wall involves the selection of the element in terms of acoustics, strength, economy and sometimes also thermal. In terms of acoustics, attention should be paid to the parameters of sound insulation from airborne sound, both required and declared by the manufacturer.

For example, the required sound insulation for walls between apartments R "A1³ 50 dB[1],while manufacturers of wall construction materials provide values; Rw /RA1/RA1R/ R "A1. All these values are correct and for an example wall can be respectively; 58/ 57 /55/ from 51 to 54 dB. And all this is calculated according to simple formulas.

RA1= Rw+C / RA1R= RA1-2/R "A1= RA1R-K where; C is the spectral index given by the RW value, i.e. the sound insulation index determined in an acoustic laboratory. Minus 2 is a correction for using laboratory test data.
K is a correction that reduces sound insulation due to lateral transmission through walls and ceilings. This correction should be calculated according to the standard, however, it was previously taken from the table, where for solid walls it was determined at a level of -1 to -4. It should be remembered that the authoritative index is R "A1.

In the simplest terms - the value refers to three concepts:

  • the calculated index of sound insulation of the partition,
  • the required indicator in accordance with the standard[1],
  • the measured index on the built object.


[1] PN-B-02151-3:2015-10 Building acoustics - Protection against noise in buildings - Part 3; Requirements for acoustic insulation of partitions in buildings and building elements

Walls between apartments

The Leca® BLOK wall element systemhas beenmanufacturedin Poland for more than twenty years. Keramzite concrete blocks have in their composition granules of lightweight expanded clay, which, thanks to their porous internal structure, support the properties of absorption of sound waves passing through the partition. This property makes it possible to produce lighter elements than other products in the same class of sound insulation.

LB 18 g

LB 18 g


In addition, walls made of expanded concrete blocks already with a thickness of 18 cm allow to achieve sound insulation of more than 50 dB. The most well-known product is the Leca®BLOK acoustic 18g block. The wall thickness of 18 cm + 2 x 1.0 cm of gypsum plaster allows to reduce the thickness of interior walls from the popularly used 24 cm + 2 x 1.0 cm by 6 cm. This is not much for a single wall, however, in a multi-family building, the walls separating apartments are many. Less wall thickness means more usable space. And a larger apartment area means convenience for users and real profit for the Developer.

Walls separating apartments
from corridors and stairwells

Walls separating apartments from corridors and staircases must additionally meet the requirement of thermal insulation U ≤ 1 W/m2K. Simultaneous provision of thermal and acoustic insulation is reconciling fire and water. As a rule, heavy materials are good sound insulators while light ones provide good thermal insulation. Until now, most of the walls separating apartments from corridors and staircases were made as layered walls made of acoustic blocks and insulation boards not infrequently covered with gypsum boards on the side of the staircase or corridor. Such walls were about 26-28 cm thick and the cladding on the cage was susceptible to damage, for example, when bringing in furniture, bicycles, etc.




In 2021, after several years of research, the new Leca® BLOK acoustic block 22 KKS was introduced into the Leca® BLOK system. The blocks, measuring 30 x 22 x 24 cm, allow walls to be built with a thickness of 22 cm plus 2 x 1.0 cm gypsum plaster on both sides. The block has a shaped pocket for filling with 4 cm thick mineral wool with ʎ ≤0.039 W/mK. The weight of the block is approx. 21.5 kg, and the consumption is 12.9 blocks per 1m2 of wall.

These blocks are mainly dedicated to the erection of infill and structural walls, separating apartments from corridors and stairwells in multi-family housing. A plastered wall made of these elements achieved an acoustic insulation of Rw = 58 (-1;-5) dB, which allows to achieve R "A1 insulation of 51-54 dB (the required minimum of 50 dB). An additional wool insert allows for a thermal insulation of U = 0.858 W/m2K (required maximum of 1 W/m2K). The finished wall after plastering has a thickness of only 22+2x1.0 = 24 cm. In other layered wall solutions, the thickness of this type of wall is usually greater and the labor intensity is more expensive.

TheLeca® BLOK acoustic block 22 KKS was applied for in the Patent Office of the Republic of Poland under No. P.43661. The application concerns both the product itself and the method of making the wall. The idea for such a product was born several years ago. In order to achieve good both thermal and acoustic insulation, a number of expensive tests were carried out on several other prototype products. The application was made in order to reduce the possibility of uncontrolled counterfeiting of blocks,and thus protect Investors and Contractors from the consequences of using technically untested products.

Tight masonry

Remember that in acoustics we are dealing with sound, or more precisely with acoustic pressure. Pressure, on the other hand, is worth associating in this case with the pressure in the wheels of a car. Tight tires mean trouble-free driving. One hole in the tire means trouble on the road. And so it is in construction acoustics. A small leak between masonry units is a reduction in sound insulation by several decibels.

Leca® BLOK acoustic blocks are used to make walls with high acoustic insulation, especially in multi-family housing. Walls should be built with full horizontal and vertical joints using cement-lime mortar. When dealing with a block that has a tongue-and-groove profile, this joint should also be filled with mortar. The required thickness of the joint is 10-15 mm. The mortar should be spread by hand.

Szczelne murowanie

Tight masonry


Depending on the type of wall and the guaranteed strength of the block, the appropriate mortar should be used for masonry. For load-bearing and structural walls, the brand of mortar must be in accordance with the accepted structural calculations. For partition and infill walls, the mortar should have a strength close to that of the blocks.

When connecting walls made of Leca® BLOK acoustic blocks with other walls, typical masonry ties(stiles) should be made in every second or third layer. Connections of perpendicular walls on the so-called "contact" and connections with metal fasteners do not provide the expected acoustic insulation.

In the case of infill walls during masonry, the gaps under the ce ilings should be reduced as much as possible by thickening the last horizontal joints. The gap under the ceiling should not be more than 2 cm. First fill the gap on one side with mortar for approx. 1/5 of the thickness of the masonry. Then, after the mortar dries, from the other side fill the free space very tightly with mineral wool leaving a gap of approx. 1/5 of the thickness of the masonry and also fill this gap with mortar. It is not recommended to fill the gaps with expanding foam from a tube or polystyrene strips. It is permissible to use systemic sealing solutions (putty and bandages).

On the walls, the number of furrows of sockets and boxes recessed into the masonry should be kept to a minimum. In addition, sockets and boxes must not be made in the same place on the so-called "space" on both sides of the wall. The recommended distance between possible installation boxes and furrows on one as well as on both planes of the wall should not be less than 60 cm.

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