The minimum requirements
Minimum sound insulation under building regulations law is governed by the relevant standard, whose first part contains the requirements and whose further parts describe the verification procedure. Its parts separate the requirements from the verification methods.
That minimum must be met in every case. It serves protection against health hazards and unreasonable disturbance, not comfort.
The revised standard largely retained the level of requirement of its predecessor. In individual areas it was nonetheless raised, expressly in view of decisions of the Federal Court of Justice, for instance on impact sound through floors and on sound insulation in semi-detached and terraced houses.
A note on method: spectrum adaptation terms and insulation across an extended frequency range are not taken into account in the official verification procedure in Germany. They are nonetheless significant for perceived quality.
Meeting the minimum does not exclude a defect
This is the central point and the reason this article exists. It concerns the relation between consentability and conformity with the contract.
| Level | Standard |
|---|---|
| Public law | the minimum of the standard; observing it does not mean the work conforms to the contract |
| Contract | what is owed are the recognised rules of technology and the agreed characteristics |
What governs contractually is therefore the expectation the contract justified. It follows from the building description, the price level and the statements made in marketing.
The system of the recognised rules is covered in the article on recognised rules of technology. It also sets out when a standard has that rank at all.
The bodies of rules for enhanced requirements
Several bodies of rules give guide values for insulation above the minimum. None of them applies without agreement.
| Body of rules | Content |
|---|---|
| Part 5 of the relevant standard | enhanced sound insulation |
| Supplementary sheet 2 to the standard | guide values for enhanced insulation |
| VDI guideline | three insulation grades with rising requirements |
| Further specifications | supplementary guide values |
One point deserves particular attention. The lowest grade of the VDI guideline already sits around 3 decibels above the requirements of the minimum standard and therefore well above the statutory minimum. The two higher grades sit far above it.
Agreeing the lowest grade of a body of rules for enhanced insulation therefore already means agreeing considerably more than the minimum. That bears on contract drafting and on cost work.
What belongs in the contract
The conclusion is simple and nonetheless rarely drawn. The sound insulation owed belongs expressly agreed, and before the contract is concluded.
Four entries make the agreement robust. They belong in the contract rather than in the building description.
| # | To be stated | Why |
|---|---|---|
| 1 | The body of rules and its edition | several exist side by side and are updated |
| 2 | The level or grade of requirement | where the body of rules recognises more than one |
| 3 | The elements concerned | requirements differ between party walls, floors, stairwells and internal elements |
| 4 | Sound insulation within the dwelling itself | it differs from the requirements between units and is frequently forgotten |
Without these, a dispute turns on an expert's view of what expectation was justified. The outcome is open and the route there expensive.
The link with fire safety
Sound insulation and fire safety concern the same elements, and their requirements do not always run in parallel. A construction must satisfy both requirements at once.
A separating wall between two dwellings must provide both fire resistance and airborne sound insulation. A floor construction concerns structural safety, fire resistance, impact sound and airborne sound at once.
The strictest of the requirements involved always governs. For cost work it follows that an element must be assessed against the bundle of requirements rather than against a single certification.
The article on fire safety evidence covers the other side. It also sets out how elements are classified.
What follows for cost work
Two points are regularly underestimated in early assessments. Both concern the transferability of benchmarks.
| Point | Cost effect |
|---|---|
| Enhanced sound insulation is not a surcharge but a different construction | it acts on wall build-ups, floor build-ups, screeds and services at once |
| Benchmarks presuppose a level | a benchmark from a project with minimum insulation does not transfer to one with enhanced insulation |
Related articles
This article reflects the position of the rules and case law at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace assessment of the individual case.