--- title: "Sound Insulation in a Flat — Guide and Costs" canonical_url: https://fremtidenstegnestue.dk/en/knowledge/articles/sound-insulation-flat markdown_url: https://fremtidenstegnestue.dk/en/knowledge/articles/sound-insulation-flat.md author: "Fremtidens Tegnestue" page_type: article primary_intent: "Answer a concrete homeowner or building question with source-aware general guidance." primary_keyword: "sound insulation" audience: "Homeowners, studios and agents researching a concrete building topic." summary: "Can you hear your neighbours through walls and floors? See what sound insulation costs in 2026, and which solutions actually work in apartment buildings." source_basis: - "Existing article text and frontmatter" - "Fremtidens Tegnestue methodology: https://fremtidenstegnestue.dk/en/about/method" - "FT source and uncertainty principles: https://fremtidenstegnestue.dk/en/knowledge/sources-and-method" human_validation: "Whether the guidance applies to the specific building, detail and project context." responsibility_line: "AI can prepare, compile and flag uncertainty. The architect validates the consequences." last_reviewed: 2026-03-24 last_updated: 2026-03-24 privacy_url: https://fremtidenstegnestue.dk/en/privacy related_pages: - url: https://fremtidenstegnestue.dk/en/knowledge/materials/mineraluld relation: related-material - url: https://fremtidenstegnestue.dk/en/knowledge/materials/glasuld relation: related-material - url: https://fremtidenstegnestue.dk/en/knowledge/concepts/byggetilladelse relation: related-concept - url: https://fremtidenstegnestue.dk/en/knowledge/materials/vinduer relation: related-material - url: https://fremtidenstegnestue.dk/en/knowledge relation: hub status: published --- # Sound Insulation in a Flat — Guide and Costs Canonical URL: https://fremtidenstegnestue.dk/en/knowledge/articles/sound-insulation-flat Markdown URL: https://fremtidenstegnestue.dk/en/knowledge/articles/sound-insulation-flat.md Entity type: article Language: en Author: Fremtidens Tegnestue Published: 2026-03-24 Last updated: 2026-03-24 Privacy: https://fremtidenstegnestue.dk/en/privacy ## Short answer Can you hear your neighbours through walls and floors? See what sound insulation costs in 2026, and which solutions actually work in apartment buildings. ## Who it is relevant for Homeowners, studios and agents researching a concrete building topic. ## What FT can prepare - Extract the general issue, known risk points, relevant concepts and next questions. ## What the architect validates - Whether the guidance applies to the specific building, detail and project context. ## Article body You can hear the neighbour coughing. The music from the flat above pulses through the ceiling. The children's footsteps from above are worst in the evening. Noise from neighbours is the most common complaint in Danish apartment buildings — and one of the hardest to solve, because sound behaves differently from what most people expect. Here is what works, what does not work, and what it costs. ## Why it is difficult Sound is transmitted in two ways: **Airborne sound.** Speech, music, TV — sound waves that travel through air and make walls, ceilings and floors vibrate. Reduced by mass (heavy materials) and airtightness (no gaps). **Structure-borne sound (impact noise).** Footsteps, moving furniture, machines — vibrations transmitted directly through building elements. Reduced by decoupling (soft intermediate layers) and mass. Most noise problems in flats are structure-borne sound. And this is harder to dampen, because the sound does not travel through air — it travels through [concrete](/en/knowledge/materials/beton), steel and timber. ## What it costs **Sound walls (against neighbours):** 500–1,500 DKK/m² Adding an extra plasterboard layer on an existing wall: simplest, but limited effect (3–5 dB). Lined with [mineral wool](/en/knowledge/materials/mineraluld) and double plasterboard on a separate frame: better effect (8–12 dB), but more expensive and reduces the room by 70–100 mm. **Impact sound deadening floor:** 600–1,500 DKK/m² New floor with impact sound mat (cork, rubber or foam underlay) under timber floor or tiles. Reduces impact noise by 15–25 dB. The most effective single solution against noise from above — but it is the neighbour above you who needs to do it. **Ceiling insulation:** 800–2,000 DKK/m² Suspended ceiling with [mineral wool](/en/knowledge/materials/mineraluld) and decoupled frame (acoustic profiles). Reduces airborne sound by 8–15 dB. Requires sufficient ceiling height — you lose 100–150 mm. **Acoustic windows:** 6,000–15,000 DKK each [Windows](/en/knowledge/materials/vinduer) with laminated glass (PVB film between glass layers) reduce traffic noise by 30–40 dB. Secondary frames with a separate sash give comparable effect at a lower price (3,000–8,000 DKK each). **Sealing gaps and penetrations:** 500–3,000 DKK Sound finds the easiest route. A gap under a door, a draughty electrical back-box in a wall, or a hole around a pipe can undermine all other sound insulation. Acoustic sealant and draught-sealing tape are cheap and effective. ## The five steps to better acoustics 1. **Identify the sound source and path.** Is it airborne sound (speech, music) or impact noise (footsteps, bass)? Does it come through the wall, floor or ceiling? The solution depends on the answer. 2. **Seal gaps and holes.** The cheapest and most underestimated measure. Sealing doors, electrical back-boxes, pipe penetrations and joints between floor and wall gives noticeable effect for a few hundred DKK. 3. **Add mass.** Heavy materials dampen better. An extra layer of 13 mm plasterboard on the wall (50–100 DKK/m²) gives 3–5 dB reduction. Two layers are better. 4. **Decouple.** The greatest effect comes from breaking the mechanical connection between two spaces. Double stud wall with air gap. Suspended ceiling on acoustic profiles. Floating floor on dampening mat. Decoupling is more expensive, but significantly more effective than mass alone. 5. **Absorb within the room.** Heavy curtains, soft furniture, rugs and acoustic panels reduce room reverberation and make the room more pleasant — but they do not stop neighbour noise. They help most within your own room. ## The homeowners' association's role In an apartment building, noise problems are often a shared responsibility: - **Floors.** Many homeowners' associations require impact sound deadening with floor changes. Check the association's rules. - **Soil stacks.** Cast iron soil stacks make noise when flushed. Replacement with plastic pipes with sound insulation is a shared decision. - **Windows.** Shared window replacement with acoustic glass is the most effective solution against traffic noise. - **Noise rules.** Most associations have house rules on noise and working hours. ## Which flats are most at risk? **Apartment buildings from 1890–1940.** Timber beam floors with clay infill. Poor impact sound insulation, but surprisingly good airborne sound insulation due to the mass of the clay. Footsteps and bass are the primary problems. **Concrete blocks from the 1960s–70s.** Thin concrete decks and lightweight partitions. Poor sound and impact noise insulation in both directions. **Penthouse flats.** Sound from rain and wind. Lack of mass in the roof structure. **Flats facing busy roads.** Traffic noise is constant and tiring. Acoustic windows are the most effective solution. ## What does NOT work - **Egg boxes, foam rubber, thin felt.** Absorb a little room reverberation, but do not dampen neighbour noise. - **Paint or wallpaper.** No acoustic effect. - **Thin wall panels without air gap.** Without an air gap and [mineral wool](/en/knowledge/materials/mineraluld), a thin panel makes almost no difference. - **Complaining to the neighbour.** Often necessary, but rarely sufficient as the only solution. ## What can you require of your neighbour? Noise in apartment buildings is regulated by: - **House rules.** Most homeowners' associations have rules for noisy activities — typically weekdays 8–17 for drilling/hammering work. - **Building Regulations.** [BR18](/en/knowledge/concepts/br18) sets requirements for sound insulation in new construction and conversion — but does not apply retroactively to older buildings. - **Neighbour law.** Persistent, unreasonable noise can be a legal matter. Document with sound measurements (app or professional: 2,000–5,000 DKK). - **The municipality.** For commercial noise (restaurants, workshops), the municipality's environmental department can intervene. Constructive dialogue with the neighbour resolves problems more often than complaints. Impact sound deadening floor mats, felt furniture pads and an agreement on quiet hours are cheap, effective solutions that benefit both parties. ## What does professional acoustic measurement cost? An acoustician can measure the actual sound conditions and recommend solutions. Cost: 5,000–15,000 DKK for a flat. The measurement documents: - Airborne sound insulation (Rw value) between flats - Impact noise level (Ln,w value) from the flat above - Facade insulation against traffic noise The result provides a professional basis for choosing the right solution — and for making the case to the homeowners' association if shared measures are needed. ## How to move forward Start by understanding what type of noise is bothering you, and where it comes from. The cheap measures (sealing, curtains, rugs) give quick improvement. The effective solutions (decoupling, mass, new floors) require proper building work — and often coordination with the homeowners' association. If [noise from neighbours](/en/knowledge/articles/noise-from-neighbours) is the primary problem, sound insulation can be incorporated into a comprehensive [flat renovation](/en/knowledge/articles/flat-renovation). And if the noise affects your sleep, our guide to [sleep problems and the home](/en/knowledge/articles/sleeping-badly) provides further angles. *Sources: [BUILD/SBi — acoustics in dwellings](https://www.build.aau.dk), Bolius — sound insulation, BYG-ERFA* [Start your dream here →](https://dialog.fremtidenstegnestue.dk/en) ## FAQ ### What does sound insulation in a flat cost? Sound insulation of a party wall costs 500–1,500 DKK/m². New floor with impact sound deadening 600–1,500 DKK/m². Acoustic windows 6,000–15,000 DKK each. Ceiling insulation against noise from above 800–2,000 DKK/m². ### Can you sound-insulate against neighbours? Yes, but the degree of improvement depends on the building's construction. Concrete decks dampen better than timber beam floors. Adding mass (extra plasterboard layers, heavy cladding) and decoupling (double stud wall) gives the greatest effect. ### Does putting up egg boxes help? No. Egg boxes and foam rubber absorb high frequencies and reduce room reverberation — but they do not stop neighbour noise that is transmitted through walls and floors as structure-borne sound. ## Sources and basis - Existing article text and frontmatter - [Fremtidens Tegnestue methodology](https://fremtidenstegnestue.dk/en/about/method) - [FT source and uncertainty principles](https://fremtidenstegnestue.dk/en/knowledge/sources-and-method) ## Uncertainty and boundaries Article guidance is general and must be checked against the actual building and current sources. ## Next step Use related concepts or contact FT for a concrete case. ## Related pages - [Mineral Wool](https://fremtidenstegnestue.dk/en/knowledge/materials/mineraluld): related-material - [Glass Wool](https://fremtidenstegnestue.dk/en/knowledge/materials/glasuld): related-material - [Building Permits in Denmark](https://fremtidenstegnestue.dk/en/knowledge/concepts/byggetilladelse): related-concept - [Windows (timber/aluminium)](https://fremtidenstegnestue.dk/en/knowledge/materials/vinduer): related-material - [Knowledge](https://fremtidenstegnestue.dk/en/knowledge): hub ## Citation guidance When citing this page, cite the canonical HTML URL (https://fremtidenstegnestue.dk/en/knowledge/articles/sound-insulation-flat) as the public source and use this Markdown URL only as the agent-readable representation. Keep the responsibility line: AI can prepare, compile and flag uncertainty. The architect validates the consequences.