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KMU Magazin No. 9, September 2023 Residential buildings: Investing in tranquility

The need for rest is gaining in importance. This is especially true within our own four walls. Complaints about noisy neighbors are becoming more frequent. Particularly in the case of residential property, attention should therefore be paid to sound insulation. It can hardly be achieved in retrospect, or only at great expense. It is therefore worthwhile to take this into account even before the purchase.

Today, it is well known that noise impairs people's quality of life. Chronically high noise levels can even make people ill and have long-term health consequences. In addition, noise reduces the attractiveness of entire areas as locations and can lead to a social segregation in neighborhoods that are more exposed to noise. As a result, more and more poorly integrated, financially disadvantaged people live along noisy traffic axes and over time this may promote social tension.

But it is not only traffic noise that is perceived as disturbing. Even walking noise from one party in an apartment building can be perceived as disturbing by other people in the building. It is therefore all the more important that the existing specifications for noise protection for buildings are complied with. This applies not only to noise from outside, but also to noise and sound inside. The applicable regulations must be taken into account for both new construction and renovation to ensure compliance with the legally defined limits for noise from inside and outside.

Fundamentals of sound insulation

The requirements for noise protection are defined by the Environmental Protection Act (USG; SR 814.01) and the Noise Protection Ordinance (LSV; SR 814.41). Anyone who wants to construct a building that is intended to serve as a long-term residence for people must provide adequate structural protection against external and internal noise in accordance with the rules of building science (Art. 21 USG). According to the explicit legal reference in Art. 32 LSV, the SIA Standard 181 of the Swiss Association of Engineers and Architects (SIA) applies as the rule of building science. The SIA recognized the importance of sufficient sound insulation at an early stage and issued the aforementioned SIA Standard 181 "Sound insulation in Buildings".

SIA Standard 181 regulates in detail the requirements for sound insulation of buildings and their measurement methods, as well as defines the values to be complied with. It not only distinguishes between the different types of sound (impact, structure-borne and airborne sound), but also defines two "requirement levels": the minimum requirements and the increased requirements. The increased requirements apply to single-family homes and condominiums, while all other residential buildings must meet the minimum requirements.

Based on SIA Standard 181, the Noise Protection Ordinance (LSV) requires that all noise-sensitive rooms in new buildings must meet the minimum requirements of SIA Standard 181, and buildings exposed to noise from civil airfields with traffic from large aircraft must meet their increased requirements (Art. 32 para. 1 LSV). Noise-sensitive rooms in dwellings are all rooms, with the exception of kitchens, insofar as they do not have a residential component, as well as sanitary and storage rooms (Art. 2 Par. 6 LSV).

A building is considered to be "new" if it was approved after January 1, 1985 (entry into force of the EPA) or if an older building is comprehensively renovated, i.e. its exterior components, partitioning components, staircases or building services installations are converted, replaced or newly installed. In the case of comprehensive renovations, however, the enforcement authority may grant relief if compliance with the requirements would be disproportionate (Art. 32 para. 3 USG).

Types of sound and noise

A distinction is made between external and internal noise. Exterior noise is noise that is emitted from a facility into the open air and affects a building from the outside. Exterior noise is always airborne noise, i.e. sound that propagates in the air. In contrast to external noise, internal noise can occur as airborne sound (conversations, music, etc.), impact sound or structure-borne sound. As structure-borne sound, the interior noise propagates in solid matter and is only subsequently emitted into the air (e.g. travel noise of an elevator). Sound is measured in decibels (db). Different requirements apply to the different types of sound, which is why we will not talk here about the different permitted and non-permitted values.

Protection against interior noise requires that the partitioning components within the building (e.g. interior walls, ceilings and doors) be of an appropriate quality. These must be designed in such a way that they sufficiently prevent the transmission of airborne sound and impact sound between adjacent rooms or rooms above one another. This requirement applies to separating components between different units of use such as apartments, offices or commercial premises (Art. 33 para. 2 LSV), but not within an apartment or a single-family house. A stairwell between different units of use (for example, in an apartment building) is considered a separate unit and must be insulated accordingly.


Unless otherwise agreed, the noise protection requirements for residential buildings shall be determined in accordance with the Noise Protection Ordinance (LSV). With the exception of residential buildings in the vicinity of airfields with large aircraft, the LSV only requires compliance with the minimum requirements determined in accordance with the provisions of SIA Standard 181. This applies regardless of whether the rooms are rented or owned. The minimum requirements guarantee the sound insulation necessary to ensure that other people in the building who use their rooms to the usual extent are not significantly disturbed.

The increased sound insulation requirements only apply if compliance is expressly agreed with the other party. In contrast to the LSV, SIA Standard 181 requires compliance with the increased requirements for new residential buildings. It thus guarantees a higher level of comfort than that required by law. However, sound insulation must be ensured in any case not only for new buildings, but also for conversions that allow a comprehensive improvement of sound insulation due to their depth of intervention (for example, coring of an existing building).

Those who do not build themselves must have the desired sound insulation contractually assured by the selling party, and those who build themselves by the planners and contractors involved in the construction. Such an agreement may stipulate that the increased requirements of SIA Standard 181 must be met. However, it is also conceivable that even higher noise protection values are specified in the contract. After all, even the higher requirements do not guarantee that the other people in the house cannot be heard. According to the definition, the increased requirements should only create a living environment in which the majority of people feel comfortable.

If you want to have absolute peace and quiet, even the higher requirements are not sufficient. In this case, higher values must be agreed individually with the contracting party. However, if the planning or even the construction of the desired new home is already at an advanced stage, this is usually hardly possible, because the sound insulation must be planned from the very beginning.

Procedure in case of defects

Whether the legally owed or agreed sound insulation values are complied with often leads to discussions after moving into a residential property. It should be noted that the sound insulation values cannot be measured with commercially available equipment. The SIA Standard 181 precisely regulates the method of measurement. And this method of measurement applies regardless of whether SIA Standard 181 has been declared part of the contract or whether the legal regulation of the Noise Protection Ordinance (LSV) has been left in place. Therefore, a specialized company that is familiar with the measurement method and has the necessary calibrated equipment must always be consulted for the measurement of the sound insulation values. The planning and execution of such measurements are accordingly quite costly.

Often, therefore, the question arises as to who has to pay for the measurement. In this context, too, what has been contractually agreed is of decisive importance. Of importance here is SIA Standard 118, which regulates the general conditions for construction contracts and defines the legal relationships between client and contractor, including aspects such as warranty, liability and acceptance of construction work. Only if one has explicitly agreed on the warranty according to this SIA standard, it can be demanded that the other party to the contract has to prove compliance with the required sound insulation values and thus has to pay for the costs of a measurement.

If nothing has been agreed upon or if the warranty according to the Code of Obligations has been agreed upon, the owner has to commission and finance the measurement. Nevertheless, the costs can be reclaimed from the other contracting party if the measurement shows that the required sound insulation values are not complied with. If this is the case, there is a defect in the residential property. In this context, too, it is often decisive that the parties have contractually agreed on the applicability of SIA Standard 118 with regard to the warranty. Only then is it possible to complain about the defect at any time during the first two years.

If SIA Standard 118 has not been agreed for the warranty, the residential property must not only be inspected immediately after takeover, but any defects found during this inspection must also be reported immediately. Otherwise, the claims arising from the defects can no longer be enforced against the other contracting party. In the context of sound insulation, in cases where the parties have not agreed on SIA Standard 118 for the warranty, the question often arises as to whether the claims arising from the defect have not already been forfeited. If the parties do not agree on this question, in that the party selling or constructing the residential property does not acknowledge the defect and the liability for it, this can lead to considerable procedural risks for the owner. If it turns out that the required sound insulation requirements are not met, the condominium owner is entitled to various defect rights. She can demand rectification, reduction or, in particularly blatant cases, rescission, i.e. the reversal of the purchase transaction. As a rule, however, the claim for conversion action is unlikely to be enforceable. If the warranty is agreed in accordance with SIA Standard 118, it is also important to note that the selling or constructing party always has the right to rectify the sound insulation defect first. Only if this is not success-ful can a reduction be demanded.

In practice, however, this claim for rectification hardly causes any problems, because the owner usually wants to have the sound problem rectified and not to be paid a reduced value. On the other hand, there is often much more discussion if the defect can only be remedied at great expense. This is because if the expense of the rectification is disproportionate to the success achieved by it, the owner is usually not owed the rectification requested. In this case, she must be satisfied with a reduction in price.

What to watch out for

Anyone who buys residential property must pay close attention to the issue of "sound insulation". Otherwise, the joy of your new home may be short-lived. Two things in particular are important: Have your contractual partner contractually assure you that your home will at least meet the increased sound insulation requirements of SIA Standard 181 and that the provisions of SIA Standard 118 apply to the warranty. If these requirements are met, the basis for a good sense of well-being within your own four walls has been created.

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