Two winters ago I helped a friend soundproof the bedroom wall she shares with a neighbour who plays Call of Duty until 2 a.m. We packed the cavity with mineral wool, added a second layer of plasterboard, sealed every edge with acoustic sealant — and the low bass thump barely changed. Not because we did it wrong. Because the noise wasn't coming through the wall. It was coming through the floor joists, the shared chimney breast, and a gap under the skirting board she'd never noticed.
That story matters here because old houses are the worst possible starting point for soundproofing. There is no cavity to fill in a solid brick wall. Lath and plaster crumbles if you look at it wrong. And the building's acoustics were designed before anyone cared about noise from a neighbour's subwoofer. So if you want to soundproof interior walls in older homes, you need to think differently from what most guides tell you.
Key Takeaways
- Soundproofing an old wall fails most often because people treat the wrong problem — the wall is usually not the main path for noise.
- Old houses leak sound through gaps, joists, chimneys and door frames before they leak it through the plasterboard itself.
- A cheap, targeted gap-sealing job can outperform thousands spent on extra layers of mass.
- Adding mass works, but only if you decouple it from the existing structure and seal it completely.
- Never trap moisture inside an old wall without thinking about ventilation — you'll trade noise for damp.
Why old walls are a different problem entirely
Modern stud walls are forgiving. There's a cavity you can fill, a clear structure you can add to, and materials that were engineered with some acoustic thought in mind. Old homes don't give you any of that.
Lath and plaster, solid brick, and no cavity
A solid brick party wall has no air gap. Sound travels through the brick, through the mortar, and radiates on the other side. You can't fill it with insulation because there's nothing to fill. And if you demolish original lath and plaster to rebuild, you're looking at a much bigger project than most people plan for — plus, in older properties, the possibility of lead paint or asbestos in older layers that needs proper handling before anyone touches it.
Old lath and plaster is also surprisingly heavy. It has real mass, which is one of the reasons it blocks mid and high frequencies reasonably well. What it does badly is stop low frequencies, and low frequencies are what keep you awake at night.
The noise paths nobody checks first
Here's what I learned from that bedroom project: you don't soundproof a wall, you soundproof a room. Sound gets in through the smallest opening before it gets in through the largest surface.
- A gap under a skirting board the width of a coin can let through more noise than an extra layer of plasterboard blocks
- Electrical sockets in the shared wall act like small speakers
- Chimney breasts and flues run through the whole building and couple noise from floor to floor
- Door frames are usually the weakest acoustic point in a room, full stop
- Floor joists under floorboards carry impact noise from a neighbour's footsteps straight into your ceiling
Before spending anything, spend a couple of evenings finding where the sound actually arrives. Put your ear against each surface while the noise is happening. Cup your hands around sockets. Listen at the base of the skirting. This diagnostic step is missing from most advice online, and it's the one that will save you money.
The cheap fixes that actually work
Soundproofing a wall cheaply in an old house means prioritising sealing before mass. Acoustic energy leaks through holes with almost no resistance, and even a small gap undoes a lot of expensive work.
What you'll need for a basic pass: acoustic sealant, a couple of tubes of it, some neoprene or foam gasket strip, door draft excluders that actually seal (not the flimsy brush type), and a tube of patience. That's it.
Sealing gaps and flanking paths
Run a bead of acoustic sealant around the perimeter of the wall where it meets the floor, ceiling and any adjoining walls. Seal behind skirting boards where you can reach. Pull back the faceplate of every socket on that wall, check whether the back box has a hole behind it into the cavity or the neighbouring room, and if it does, seal around the edges of the box with acoustic putty.
Fit a solid-core door or add a layer of mass to the existing one, and seal the frame with a proper gasket. In the case of that friend's bedroom, replacing a hollow door with a solid one and fitting a compression seal around the frame cut the perceived noise from the landing more than anything else we did.
What soft furnishings will and won't do
Heavy curtains, rugs and soft furnishings absorb reflections inside a room. They make a space feel quieter and less echoey. They do almost nothing to stop noise coming through a wall.
This is one of those distinctions that gets blurred in a lot of advice. If your complaint is a harsh, echoing room, soft furnishings help. If your complaint is a neighbour's television, they don't. Honest answer: they're worth doing for comfort, not for soundproofing.
Adding mass the right way
If sealing hasn't been enough, you're into adding mass — and this is where old houses get tricky. Mass works. Doubling the weight of a wall reduces how much sound passes through it. But if you bolt new layers rigidly to an old wall that's already transmitting vibration, you can make things slightly worse in some frequency ranges and you'll definitely add stress to old fixings that weren't designed for the load.
Resilient bars and decoupling
The professional approach is to decouple the new layer from the old wall with resilient channels or acoustic hangers, then add mass on top. This is effective — meaningfully more effective than mass alone — but it eats depth. In a small room, losing 6–8 cm off one wall is a real cost, and in a listed or period property you may not be able to do it at all without consent.
My honest opinion: for most old houses, decoupled construction on the party wall is the only approach that makes a lasting difference to low-frequency noise. Everything else is partial. I'll die on that hill.
Acoustic plasterboard and high-density panels
Acoustic plasterboard is denser than standard board and easier to install than a full decoupled system. On its own, it gives a modest improvement. Combined with a second layer and a damping compound between them, the gain is more noticeable — again, provided the perimeter is sealed completely.
The catch: every extra layer needs to be supported by structure that can carry it. Old timber studs may already be under-spec for the existing lath and plaster. Check before you load them further.
Comparing your options honestly
| Approach | Best for | Realistic improvement | Cost & disruption |
|---|---|---|---|
| Seal gaps, sockets, skirting | All noise types, must be first | Noticeable, sometimes large | Very low, a weekend |
| Heavy curtains, rugs | Echo and internal reflections | Minimal for external noise | Low |
| Extra acoustic plasterboard | Mid and high frequencies | Moderate | Moderate, needs support |
| Damping compound between layers | Broadband improvement | Better than board alone | Moderate |
| Decoupled resilient system | Low frequency, party walls | Best available | High, loses floor space |
Notice what's missing: magic materials. There isn't one. The gains come from combining approaches, and from being thorough at the cheap end before spending at the expensive end.
Questions readers keep asking
Does Home Depot sell soundproof drywall?
Home Depot carries acoustic and sound-rated drywall in many of its stores and via its website, but availability varies considerably by location and by product line. Call your local branch before making the trip — the range on the shelf is not the same as the range listed online. What you'll typically find is denser plasterboard rather than a dedicated "soundproof" board, and it still needs careful installation and sealing to perform.
How can I soundproof my walls?
Start by finding the actual noise paths, then seal every gap, joint and penetration along those paths. After that, add mass — either acoustic plasterboard or a decoupled layer — and make sure the whole assembly is airtight. No single step soundproofs a wall on its own; the combination does the work.
Do you have to cover the whole wall for soundproofing?
No, and this is one of the most useful things to know in an old house. You can treat part of a wall successfully. Sound doesn't need the whole surface to be covered — it needs every possible path to be blocked. Covering the area where noise actually arrives, and sealing the edges of that area properly, is often enough. Covering a whole wall badly is worse than covering half of it well.
Can you soundproof a wall from noisy neighbours?
Partly, and with honest expectations. You can substantially reduce airborne noise — voices, TV, music — with the methods above. Impact noise from footsteps and furniture being dragged is a different problem, and much of it arrives through the structure rather than the wall itself. If that's your main complaint, the ceiling and floor structure matter more than the wall. In rented or shared properties, also check what the tenancy agreement or building rules say before making changes.
A note on moisture before you close anything up
Old walls breathe. They rely on vapour moving through the fabric. Adding impermeable layers to the inside face without thinking about ventilation can trap moisture, and I've seen a project where a well-insulated but badly ventilated internal wall developed damp within two heating seasons.
Before anyone adds a sealed layer to an old wall, confirm where the moisture in that room goes — a vent, a window, a working extractor. Get this wrong and you'll be dealing with mould in eighteen months, which is far worse than a noisy neighbour.
Which brings me back to that bedroom. What actually fixed it, in the end, wasn't the mineral wool or the plasterboard we installed first. It was sealing the gap under the skirting board, fitting a solid door, and sealing a socket we'd completely overlooked. Three days of careful, cheap work. The wall we'd spent a weekend on barely mattered.
So before you buy a single sheet of anything, spend one evening with your ear pressed to the plaster. The answer to where your noise comes from is already in the room, waiting to be heard — and it will tell you more than any product on a shelf ever could.
