DIN 4109 is the German standard for sound insulation in buildings (Schallschutz im Hochbau). Part 1 of the 2018 edition sets the legal minimum between flats: 53 dB for the party wall, 54 dB for the party floor and an impact sound level of no more than 50 dB. Part 5 of 2020 defines the higher level that a buyer or tenant can agree in a contract. The values below explain what a neighbour's footsteps and voice will sound like at each level.
What DIN 4109 is and why the 2018 edition is the legal minimum
DIN 4109 is the German standard for sound insulation in buildings, and Part 1 in the edition of January 2018 (DIN 4109-1:2018-01) defines the minimum sound insulation (Mindestschallschutz) that every new residential building in Germany must reach between flats, towards stairwells and against outdoor noise; the minimum applies through the state building codes and is owed even when a contract says nothing about sound. The engineering guide of KHB Ingenieure on sound insulation in housing under DIN 4109 summarises the values of Part 1 and of the enhanced Part 5.
The standard uses two measured quantities. The weighted apparent sound reduction index R'w, in decibels, describes airborne sound insulation of a wall or floor including flanking paths: a higher number means less sound passes through. The weighted normalised impact sound pressure level L'n,w, also in decibels, describes footstep noise transmitted through a floor: a lower number means quieter. R'w and L'n,w are both measured in the finished building, which is why the apostrophe appears in the symbols.
The 2018 edition replaced DIN 4109 of 1989. The presentation of the Lärmkontor consultancy on the new DIN 4109:2018 and what changed lists the differences: the impact sound requirement for party floors fell from 53 dB to 50 dB, the party wall between terraced houses rose from 57 dB to 62 dB, and the building acoustics guidance of the German timber industry notes that the minimum applies under Sections 3 and 15(2) of the model building code (Musterbauordnung, MBO).
Which decibel values DIN 4109-1:2018 requires between flats
DIN 4109-1:2018 requires a weighted sound reduction index R'w of at least 53 dB for the wall between two flats (Wohnungstrennwand), at least 54 dB for the floor between two flats (Wohnungstrenndecke), an impact sound level L'n,w of at most 50 dB for that floor, and at least 52 dB for a stairwell wall next to a habitable room, according to the KHB Ingenieure summary of Part 1. The guidance of the Informationsdienst Holz on regulations for sound insulation in timber construction, January 2023 reproduces the same figures in a comparison table and adds the values for terraces, walkways and stairs.
| Building element, DIN 4109-1:2018 | Airborne R'w | Impact L'n,w |
|---|---|---|
| Wall between two flats | 53 dB or more | not applicable |
| Floor between two flats | 54 dB or more | 50 dB or less |
| Stairwell wall to a habitable room | 52 dB or more | not applicable |
| Roof terrace or loggia above a living room | not applicable | 50 dB or less |
| Floor under an access walkway (Laubengang) | not applicable | 53 dB or less |
| Stair flights and landings | not applicable | 53 dB or less |
| Party wall, terraced or semi-detached house | 62 dB or more | not applicable |
The Lärmkontor presentation adds two values that the tables above do not show: a door from a corridor into a habitable room needs a sound reduction index of 27 dB, and a door that opens directly from a stairwell into a flat needs 37 dB. The same presentation notes that the standard now works with measured values instead of calculated ones, with a 2 dB safety margin (R'w,P minus 2 dB) for walls and floors and a 5 dB margin for doors, so a door tested at 42 dB in the laboratory is rated at 37 dB in the building.
The values apply to sound transmission between different dwellings or between a dwelling and a foreign work unit. Walls and doors inside one flat have no minimum under DIN 4109-1; a bedroom next to the same flat's bathroom is not covered, and a buyer who wants insulation there must specify a value in the contract. Sound insulation is also separate from the barrier-free requirements: a threshold-free entrance door built to the 90 cm clear width of DIN 18040-2 still has to reach the 37 dB that DIN 4109-1 assigns to a door from a stairwell into a flat, as the article on DIN 18040-2 dimensions for a barrier-free flat sets out.
How DIN 4109-5:2020 raises the requirements and what the difference sounds like
DIN 4109-5, published in August 2020 (DIN 4109-5:2020-08), defines the enhanced sound insulation (erhöhter Schallschutz) that a developer, buyer or landlord can agree in a contract: R'w of at least 56 dB for the wall between two flats, 57 dB for the floor between two flats, an impact sound level of at most 45 dB, and 55 dB for a stairwell wall, according to the KHB Ingenieure summary and the January 2023 timber-construction table. The enhanced level therefore adds about 3 dB of airborne insulation and cuts impact sound by at least 5 dB compared with the minimum.
The January 2023 guidance of the Informationsdienst Holz describes what each level means for a listener in the neighbouring flat. At the DIN 4109-1:2018 minimum, loud speech is generally understandable, speech in a raised voice is generally understandable, normal speech is generally not understandable but still audible, and footsteps are generally disturbing. At the DIN 4109-5:2020 level, loud speech is generally not understandable, raised and normal speech are not understandable, and footsteps are no longer disturbing. The guidance's comfort level (Komfort), with a 59 dB party wall, a 60 dB party floor and an impact sound level of 46 dB rated with the low-frequency spectrum adaptation term, makes normal speech inaudible and footsteps barely perceptible.
| Building element | Minimum, DIN 4109-1:2018 | Enhanced, DIN 4109-5:2020 | Comfort level, timber guidance 2023 |
|---|---|---|---|
| Wall between flats, R'w | 53 dB | 56 dB | 59 dB |
| Floor between flats, R'w | 54 dB | 57 dB | 60 dB |
| Floor between flats, L'n,w | 50 dB | 45 dB | 46 dB with CI,50-2500 |
| Stair flights and landings, L'n,w | 53 dB | 47 dB | 46 dB |
| Party wall, terraced house, R'w | 62 dB | 67 dB | 67 dB |
| Door from stairwell into flat, Rw | 37 dB | 42 dB | not listed |
The Lärmkontor presentation gives the door values of DIN 4109-5:2020 as 32 dB for a door from a corridor and 42 dB for a door from a stairwell, 5 dB above the Part 1 values. The enhanced level is voluntary: a contract for a new flat in Germany must name DIN 4109-5 or a specific decibel value, otherwise the purchaser can claim only the Part 1 minimum.
What a tenant or buyer can check and what the numbers mean for interior finishes
A buyer or tenant in Germany can check three documents: the sound insulation certificate (Schallschutznachweis) that the building application requires under the state building code, the purchase or construction contract, which must name DIN 4109-5 or a decibel value for any level above the minimum, and, after handover, a measurement report from an acoustics engineer, because DIN 4109 values are verified by measurement in the finished building. The timber-construction guidance of January 2023 states that the Part 1 minimum "darf nicht unterschritten werden und ist auch ohne Vereinbarung immer geschuldet" (may not be undercut and is always owed even without an agreement).
Interior finishes change the impact sound result more than the airborne result. The impact sound level of a floor is a property of the whole build-up, so a floating screed on an insulation layer, or a floor covering with a resilient underlay, is what brings a concrete slab from a raw value to the 50 dB or 45 dB target, and a tenant who replaces carpet with hard flooring can move the measured value in the wrong direction. Whether a tenant may make such a change, and who pays to restore the floor at move-out, is a question of the lease and of the cosmetic-repair rules explained in the article on Schönheitsreparaturen and tenant painting rules.
- Ask for the Schallschutznachweis before signing; the document names the target values for every party wall and floor.
- Read the contract for the words "DIN 4109-5", "erhöhter Schallschutz" or a stated R'w and L'n,w; without them the Part 1 minimum applies.
- For a terraced or semi-detached house, look for the 62 dB party wall of the 2018 edition rather than the 57 dB of buildings planned under the 1989 edition.
- After handover, a measurement by an engineer is the only proof; the standard rates measured values, with a 2 dB margin for walls and floors and 5 dB for doors.
How DIN 4109 fits with the other standards that shape a flat in Germany
DIN 4109 governs sound, DIN 18040-2 governs accessibility and DIN 5034-1 governs daylight, and the three standards apply to the same walls, doors and windows of a flat in Germany without replacing each other: a door that meets the 90 cm clear width of DIN 18040-2 still needs the 37 dB of DIN 4109-1 where it opens from a stairwell into a flat, and a window that meets the 55 percent glazing width recommended by DIN 5034-1 still needs the outdoor-noise rating that DIN 4109-1 assigns from the noise level range of the street.
The outdoor-noise requirement of DIN 4109-1:2018 is set from a noise level range (Lärmpegelbereich) derived from the measured or calculated traffic noise outside, with separate day and night plans in the 2018 edition instead of the 5 dB classes of 1989, as the Lärmkontor presentation explains. The window is normally the weakest element of an external wall, so the glazing width that daylight planning asks for and the sound rating that the street asks for must be resolved together; the article on daylight and window rules under DIN 5034-1 gives the daylight side of that calculation.
Frequently asked questions about building standards in Germany
The answers below repeat the figures and legal references from the article in short form, so that each answer can be read on its own.
- What is the minimum sound insulation between two flats in Germany?
- DIN 4109-1:2018 requires an airborne sound reduction R'w of at least 53 dB for the wall between two flats and 54 dB for the floor, and an impact sound level L'n,w of at most 50 dB for the floor; the minimum is owed even without a contractual agreement.
- What does DIN 4109-5 add?
- DIN 4109-5:2020 is the enhanced level: R'w of at least 56 dB for party walls, 57 dB for party floors and an impact sound level of at most 45 dB, which is 3 dB more airborne insulation and 5 dB less impact sound than the minimum.
- What are the requirements for a terraced or semi-detached house?
- DIN 4109-1:2018 requires R'w of at least 62 dB for the party wall between terraced or semi-detached houses, up from 57 dB in the 1989 edition, with 59 dB accepted for the wall section in the lowest storey.
- Does DIN 4109 apply between rooms of the same flat?
- No. DIN 4109-1 sets requirements between different dwellings or work units and towards stairwells and corridors; walls and doors inside one flat have no minimum under Part 1.
- Can a neighbour's normal conversation be heard at the DIN 4109-1 minimum?
- At the DIN 4109-1:2018 minimum, normal speech through a party wall is generally not understandable but still audible, raised speech is generally understandable and footsteps are generally disturbing, according to the verbal descriptions used in the German timber-construction guidance of 2023.