What the standard covers
The Belgian standard on acoustic criteria for residential buildings addresses four subjects. Each criterion is checked by measurement on the finished building.
Airborne sound insulation, that is voices, music and sound transmitted through air.
Impact sound insulation, that is footsteps, falling and moving objects.
Noise from building services, ventilation and equipment.
Reverberation in common circulation spaces serving several dwellings.
The criteria bear chiefly on the completed building, not on laboratory performance of materials. That is an important feature: a theoretically effective build-up poorly executed does not meet the standard.
| Subject covered | What is targeted | Method of verification |
|---|---|---|
| Airborne noise | Voices, music, sound carried by air | Measurement on the finished building |
| Impact noise | Footsteps, falls, moving objects | Measurement on the finished building |
| Technical installations | Ventilation and equipment | Measurement in operation |
| Reverberation | Common circulation serving several dwellings | Measurement on the finished building |
The confusion about binding character
This is the point deserving most attention, and professional sources contradict one another. It concerns the applicable version of the standard.
Some present the standard as having been made mandatory, relying on its publication in the Official Gazette.
Others, including the technical reference bodies, present it as applying as rules of good practice.
The second formulation is the more prudent, and the contradiction is explicable. Publication in the Gazette corresponds to approval, the act conferring on a document the status of Belgian standard. Approval does not make a standard mandatory: it gives it its status, which is different, as the article on voluntary and mandatory standards explains.
In practice the consequence is limited but real. The standard counts as good practice in all cases, which suffices to engage the liability of anyone departing from it without justification. It becomes binding in the strict sense as soon as a permit or specification cites it.
What the revision changed
A revised version was published in July 2022, applying to permit applications submitted from 1 January 2023. The version named in the contract prevails over any other.
Three structural changes.
A move to three performance classes, A, B and C, aligned on an international classification system, replacing the two comfort levels of the previous edition.
Class C is the minimum level required by the standard, higher classes following from a specific request or undertaking.
A tightened requirement between distinct new residential buildings, notably between two new terraced houses, where a level above the minimum is expected for airborne and impact sound.
A technical novelty is added: low frequencies are taken into account, driven by the growing share of lightweight construction, which performs less well there. It changes the constructive solutions to be retained.
What this imposes on construction
Three design consequences, independent of precise values. They concern the walls, the flanks and the equipment.
Decoupling becomes the rule rather than the exception. Meeting impact sound requirements between floors calls for dedicated construction measures, to be provided from structural design onwards.
Party walls call for particular treatment. Building new work against an existing party wall does not suffice; technical guidance recommends a new independent wall.
Lightweight construction demands more attention. Low-frequency requirements penalise it more than heavy construction, which may alter a decision on construction method.
Why measurement takes place at the end
A point making this field risky and justifying continuous vigilance. Conformity is measured on the finished building, not on the plan.
Since the criteria bear on the completed building, conformity is established only after completion, by measurement on site. A workmanship defect, an unplanned rigid connection or a poorly treated penetration can ruin a correctly designed build-up.
The practical consequence is that checking must happen during execution, at the sensitive points, rather than discovering the result at handover.
Those checks are covered in the article on inspection bodies. Their scope of accreditation is explained there.
What this means for a professional
Four rules.
Check what the permit and the contract cite, rather than settling the question of binding character in the abstract.
Fix the class targeted in the contract, or the minimum will apply and a client expecting better will be disappointed.
Provide the measures from structural design, since they cannot be retrofitted in finishes.
Check the applicable version, the standard having been revised and the regime depending on the date of the permit application.
This article reflects the position of the rules at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace consulting the applicable standard.