Domakihub How to Fit Acoustic Insulation in a Wall: A Step-by-Step Guide
Cut noise between rooms with the right materials, the right order, and no costly mistakes.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Noise travelling through walls is one of the most common complaints in Greek apartments, holiday rentals, and hotels — thin partition walls built in the 1970s and 1980s offer almost no sound barrier at all. The video above shows a full hands-on installation of mineral-wool acoustic batts inside a timber stud wall; this article walks through the same process in ordered steps and adds the context you need before you pick up a Stanley knife. Whether you are upgrading a bedroom in a villa for quieter guest reviews or insulating a home office against street traffic in Athens, the fundamentals are the same.
Understanding How Sound Travels Through Walls
Sound moves through a wall in two ways: airborne noise (voices, TV, music) passes through gaps and porous materials, while impact noise (footsteps, scraping furniture) travels through the solid structure itself. Most DIY acoustic upgrades target airborne noise, which is controlled by mass, absorption and decoupling — adding heavy, dense material, filling cavities with absorptive wool, and breaking the rigid connection between the two wall faces.
A stud wall filled with acoustic mineral wool can achieve an improvement of 10–15 dB Rw compared to an empty cavity, which is noticeable but not complete silence. For demanding applications — a home cinema, a recording studio, or a hotel room next to a lift shaft — a specialist acoustic contractor should model the construction and may recommend a fully decoupled 'room within a room' solution, which is beyond typical DIY scope.
Permits, Regulations and When to Call a Pro
In Greece, fitting acoustic insulation inside an existing non-structural partition wall does not generally require a building permit (οικοδομική άδεια), provided no structural element is altered and no change of use is involved. However, if the wall you plan to open is load-bearing, or if the work involves rerouting electrical conduit or plumbing buried in the wall, you must engage a licensed engineer (μηχανικός) and submit the appropriate notification to your local urban planning office (Υπηρεσία Δόμησης). Always confirm with your local authority before starting, as rules vary by municipality and building age.
Damp is the other watch-out. If you see staining, efflorescence, or smell mould before opening the wall, stop and call a damp-proofing specialist. Trapping moisture behind new insulation turns a noise problem into a structural and health problem.
Electrical work inside the wall cavity — moving sockets, adding new circuits, re-routing cables — requires a licensed electrician (ηλεκτρολόγος) with a valid installation certificate (ΥΔΕ). Plan that work before the wall is closed, not after.
How to Fit Acoustic Insulation in a Wall: 5 Steps
- 1
Assess the Wall and Gather Materials
Identify whether you have a timber stud, metal stud, or solid masonry wall — the method differs significantly. For stud walls (the most common modern partition type), measure the stud spacing (typically 400 mm or 600 mm centres in Greek construction) and buy acoustic mineral-wool batts sized to friction-fit without gaps: a 100 mm slab of glass or rock mineral wool with a density of at least 40 kg/m³ is the standard minimum for airborne sound. You will also need a heavy-layer acoustic membrane (mass-loaded vinyl or a proprietary acoustic board such as Fermacell or two layers of 12.5 mm plasterboard), acoustic sealant, resilient bar or metal hat channel if decoupling is planned, and self-tapping screws.
- 2
Remove or Open the Wall Lining
For a new or renovation wall, fix the framing first, then insulate before boarding. For an existing wall, carefully remove one face of plasterboard — score along the edges with a Stanley knife, unscrew fixings and lever gently to avoid cracking adjacent plaster. Before reaching inside, use a cable detector and pipe finder to locate any services hidden in the cavity. Mark and protect any cables or pipes with a protective conduit sleeve. Set the old plasterboard aside — it is unlikely to be reusable because the paper face tears, but recycle it at your local waste point.
- 3
Fit the Acoustic Batts
Wear gloves, safety glasses and a dust mask rated FFP2 or better — mineral wool fibres are an irritant. Cut batts with a serrated knife or a panel saw, leaving the batt 10–15 mm wider than the stud bay so it compresses slightly and friction-fits without falling out and without being forced so tight that it loses its open, absorptive structure. Work from the top of the wall downward and fill every bay, including any narrow offcuts at the edges. Push the wool back so it sits flush with the front face of the studs — bulging wool will telegraph as a hump behind the new board. If you are adding a second layer of insulation for a wider cavity, stagger the joins between layers so there are no continuous air paths.
- 4
Seal All Gaps and Add Acoustic Board
This step is where most DIY jobs lose the gains they worked for. Acoustic performance depends on airtightness: run a continuous bead of acoustic sealant (non-hardening, permanently flexible) around every perimeter — floor, ceiling, adjacent walls and around any electrical back-boxes. For maximum performance, fix a layer of resilient bar horizontally across the studs at 400 mm centres; this decouples the new board from the frame and reduces structure-borne transmission. Screw your first layer of 15 mm acoustic plasterboard to the bars (not to the studs directly if you are using resilient bar), then apply sealant to all joints and perimeter before adding a second layer with staggered joins. Tape and fill all joints with acoustic joint compound.
- 5
Finish and Test
Once the compound is dry and sanded, apply a skim coat or tape-and-joint finish, prime and paint as normal. Before handing back a room in a rental property or hotel, do a simple listening test with a radio playing at normal conversation volume in the adjacent space — you should notice a clear reduction in clarity and level. If you still hear distinct words at close range, check your perimeter seals first: a 1 mm gap at a skirting board junction can undo the performance of the entire system. For a formal acoustic rating (useful when marketing a rental as 'soundproofed'), engage an acoustic consultant to carry out an airborne sound insulation test to ISO 16283-1.
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FAQ
- Can I fit acoustic insulation without removing the plasterboard?
- Yes, but with limitations. You can add mass to the existing wall by bonding a layer of acoustic board directly to the current surface using acoustic adhesive and perimeter sealant — this is sometimes called 'direct bonding' or 'dry lining'. You gain mass but lose the filled-cavity benefit, so the improvement is smaller (typically 5–8 dB rather than 10–15 dB). It also reduces the room size slightly. For serious noise problems the full cavity-fill method is more effective.
- What is the difference between thermal insulation and acoustic insulation?
- Thermal insulation (e.g. EPS foam boards, low-density glass wool) is optimised to trap air and slow heat transfer. Acoustic insulation is mineral wool — glass or rock — with a higher density (40–100 kg/m³) that absorbs sound energy within the fibrous matrix. Some products do both jobs adequately, but if your priority is sound you should specify a product with a published NRC (Noise Reduction Coefficient) or an Rw value, not just a thermal lambda value. Low-density foam has almost no acoustic benefit.
- Does acoustic insulation need a building permit in Greece?
- For a non-structural interior partition wall with no change of use, no permit is normally needed. The work falls under minor maintenance. However, if the wall is structural (load-bearing), if you are altering the layout of a listed or heritage building, or if the renovation changes the use of a space (for example converting a storage room into a habitable bedroom), you will need to notify your local Υπηρεσία Δόμησης. When in doubt, ask a licensed civil or structural engineer before opening any wall.