If you can hear your neighbour's television through the party wall, footsteps crossing the ceiling above, or a toilet flushing next door as clearly as if it were in your own hallway, your first instinct is probably to assume that's just what new build soundproofing is like. It isn't, necessarily. English and Welsh building regulations set a legally defined minimum standard for sound insulation between separate dwellings — the wall or floor between your home and your neighbour's — and every new build must meet it, either through independent testing on site or by being built to a pre-approved "Robust Detail" specification. If the standard genuinely isn't being met, that's not an inevitable feature of modern construction — it's a snagging issue, and in some cases a building control failure, that you can and should raise.
The difficulty is that most buyers have no idea what the standard actually is, how it was verified on their specific plot, or how to tell the difference between "this is mildly more audible than I'd like" (normal, and not something any builder will fix) and "this wall does not perform anywhere near the regulatory minimum" (a genuine defect worth pursuing). This guide walks through how Part E of the Building Regulations works for new build party walls and floors, what Robust Details are and why they matter to you specifically, how to gather the kind of evidence that gets a developer to actually investigate rather than dismiss you, and what happens if a post-completion sound test shows your home falls short.
Two things are worth saying upfront. First, some sound transfer between semi-detached houses, terraces and flats is completely normal and expected — no construction method eliminates sound entirely, and the regulations don't require silence, only that transmission stays below defined thresholds. Second, a failure to meet that threshold is often invisible to the eye: it can stem from a gap behind a socket, a skirting board that breaches the acoustic seal, or flanking transmission through a shared floor junction that no amount of visual inspection would catch. That's precisely why understanding the testing regime, rather than just trusting your ears, matters if you want a case the developer has to take seriously.
How Part E sound insulation standards actually work
Part E of the Building Regulations ("Resistance to the passage of sound") applies to any wall or floor that separates one dwelling from another — so it covers party walls between semi-detached and terraced houses, and separating floors and walls between flats. It does not apply to internal walls within your own home, which is why a stud wall between your bedroom and your own bathroom can sound far more hollow than the party wall next to it; that's expected and not a Part E matter at all.
The regulation sets two separate types of performance requirement, because airborne noise (voices, music, television) and impact noise (footsteps, furniture scraping, items dropped on a floor above) behave differently and are measured differently:
- Airborne sound insulation is measured in decibels (dB) using a metric called DnT,w — broadly, a measure of how much a loudspeaker's output on one side of the wall is reduced by the time it reaches the other side. A higher number means better performance.
- Impact sound insulation (relevant to separating floors, so mainly flats and some house types with rooms above a neighbour) is measured as L'nT,w — here a lower number means better performance, because it's measuring the sound level transmitted, not the reduction achieved.
As of 2026, the typical minimum values set out in Approved Document E for new build dwellings are around 45 dB DnT,w for airborne sound through walls and floors, and around 62 dB L'nT,w for impact sound through floors — always check the current Approved Document E figures and any amendments in force for your build's regulations edition, since the applicable version depends on when the development was approved. These are legal minimums, not aspirational targets: a newly built separating wall or floor that is verified below them has failed the regulatory test that was supposed to confirm it was fit to be signed off.
The standard is a minimum performance threshold, not a guarantee of silence. Meeting Part E means normal speech is significantly attenuated and footsteps are muffled — it doesn't mean you won't hear a neighbour's subwoofer at full volume or a door slammed hard.
Crucially, these standards apply at the point of construction and are meant to be verified before the home is sold. How that verification happens — individual testing on your actual plot, or reliance on a pre-approved generic construction type — is the single most important thing to find out, because it determines what evidence already exists (or doesn't) for your specific home.
Robust Details vs pre-completion testing: two routes to compliance
Builders have two legitimate ways to demonstrate that a new party wall or separating floor meets Part E, and which route was used for your home has a direct bearing on how you pursue a complaint.
Route one: pre-completion testing (PCT)
Under this route, a sample of the actual separating walls and floors on the development is tested on site by an approved acoustic tester once built, using a calibrated loudspeaker and sound level meters, before building control will sign off the relevant plots. Not every single home is tested — a statistical sample across similar construction types on the site is usually sufficient to satisfy building control that the method of construction is performing as designed. If your plot was one of the tested ones, a test certificate should exist and can, in principle, be requested. If it wasn't tested directly, the developer is relying on the assumption that it performs the same as the sampled plots of identical construction nearby.
Route two: Robust Details
The more common route on volume new build developments is to use a Robust Detail — a specific, pre-approved wall or floor construction (a particular combination of blockwork, cavity width, insulation, plasterboard layers and isolation strips) that has already been tested extensively by Robust Details Limited and shown to reliably exceed Part E minimums when built correctly. Using a registered Robust Detail removes the need for individual pre-completion testing on each plot, because the construction method itself is the evidence of compliance — provided it is actually built exactly as specified.
This distinction matters enormously if you end up disputing a defect. If a Robust Detail was used, the regulatory compliance route accepted that the design meets the standard — so a complaint about poor sound transfer is really an allegation that the detail was not built correctly on site (a workmanship issue), which is a snagging matter for the developer to investigate and potentially remediate under warranty. If pre-completion testing was used and your specific plot was tested and passed, you have documentary evidence the wall met the standard at handover, which shifts the question to whether something has since changed (a later alteration, a gap introduced during fit-out) or whether the test was flawed. If your plot wasn't individually tested under either route, you may need to request testing to establish a factual baseline before the developer will engage seriously.
Normal sound transfer vs a genuine testable failure
This is the part most buyers get wrong in both directions — either accepting a genuine failure as "just how new builds are," or escalating ordinary, compliant sound transfer as if it were a defect. A rough guide to telling the two apart:
| What you're hearing | Likely normal (Part E compliant) | Possible testable failure |
|---|---|---|
| Neighbour's TV/music | Muffled, bass-only, indistinct voices at normal volume | Clearly intelligible speech or music at normal household volume through the wall |
| Footsteps from above | A dull, soft thud, barely noticeable during the day | Sharp, loud impacts audible throughout a room, especially at night in bedrooms |
| Conversation | You can tell people are talking but not what's said | Individual words and sentences clearly audible at conversational volume |
| Doors/drawers | A dull bump occasionally | Startling, sharp bangs that sound like they're in your own room |
| Plumbing/flushes | A faint, brief sound of water movement | Loud, sustained flushing or shower noise clearly traceable to next door |
None of this is a substitute for a proper acoustic test — your ear is a poor, subjective instrument, and perception of loudness varies hugely by time of day, background noise and how sensitive you personally are to particular frequencies. But as a filter for deciding whether it's worth pushing for a test, this kind of pattern matters: compliant walls still transmit some sound, but they should meaningfully attenuate speech and impacts, not merely soften them slightly.
If you can hold a normal conversation with your neighbour through the wall without raising your voice on either side, that is a strong indicator of an actual installation defect, not a design limitation.
Also worth separating out: sound transfer that is loud because your neighbour is being genuinely unreasonable (late-night parties, subwoofers at volume, children running) is a behavioural and possibly environmental health or lease-covenant issue, not a construction defect — no wall built to any residential standard will make that inaudible. Keep a clear mental (and written) distinction between "this wall transmits too much of normal, reasonable household noise" and "my neighbour is being loud" when you're deciding what to raise with the developer versus what to address directly or via the managing agent.
Common causes of acoustic failure in new build homes
When a separating wall or floor does genuinely underperform, it's almost always a workmanship issue rather than a design flaw — Robust Details and tested wall types are engineered with margin above the minimum standard precisely because real-world site conditions introduce small losses. The most frequent culprits found by acoustic consultants investigating new build complaints include:
- Flanking transmission — sound bypassing the separating wall or floor entirely by travelling through a continuous element that runs past it, such as a floor screed, skirting board, or service void that wasn't properly broken or isolated where it meets the party line.
- Service penetrations — electrical sockets, light switches or pipework installed back-to-back on opposite sides of a party wall, or holes cut for cabling, that create a direct acoustic bridge through what should be a continuous barrier.
- Missing or compressed isolation strips — the resilient strip that should sit between a floating floor and the surrounding walls/skirting to stop impact noise transferring into the structure; if it's missing, crushed, or bridged by a nail or screw, impact performance collapses.
- Incomplete cavity fill or wrong insulation — a party wall cavity partially filled, or filled with the wrong density or type of mineral wool, reduces airborne performance even if the rest of the wall looks correct.
- Loft void bridging — in houses, sound travelling over the top of the party wall through a shared, uninterrupted loft space where the fire/acoustic barrier wasn't properly built up to the roof line.
- Doors and hatches in the wrong place — loft hatches, built-in wardrobes or cupboards positioned directly against a party wall can thin the effective barrier at that point.
- Poor sealing at junctions — gaps around the perimeter of a separating wall or floor where it meets external walls, ceilings or the roof structure, which should be fully sealed with acoustic sealant but sometimes aren't.
Because most of these causes are hidden inside the structure, you generally cannot diagnose them yourself by inspection. What you can do is document the pattern of noise carefully enough to give an acoustic tester or the developer's technical team a strong starting hypothesis — for example, noting that the problem is worst near a particular socket, or close to where a wardrobe sits against the party wall, can point investigators straight at the likely cause.
Building the evidence before you raise it as a defect
Developers deal with a steady stream of noise complaints that turn out to be ordinary living sounds, so a vague "I can hear everything" email is easy to deflect. A well-documented complaint, by contrast, is much harder to wave away. Before you contact the developer or site manager, try to gather:
- A noise diary. Log date, time, duration, what you heard, which room, and how it compared to background noise — kept consistently over at least two to three weeks, ideally covering different times of day.
- Specific, repeatable examples. "Every evening between 9pm and 10pm I can hear my neighbour's television dialogue clearly enough to follow the programme while sitting in my living room" is far more actionable than "it's really bad at night."
- Location mapping within the room. Note whether the sound is loudest near a particular wall, socket, or piece of fitted furniture — this can point directly at a flanking or penetration issue.
- A basic comparison. If you have access to a smartphone decibel meter app, rough readings (with the caveat that phone apps aren't calibrated instruments and won't stand as formal evidence) can still help you describe intensity more objectively than "loud."
- Confirmation of the construction method. Ask the developer, in writing, whether your separating wall/floor was built to a registered Robust Detail (and request the registration number) or was covered by pre-completion testing (and request the test certificate, if one exists for your plot or the sampled plot type).
- Your build date and regulations version. This affects which edition of Approved Document E and which Robust Details catalogue applies.
The single most useful document you can obtain is the Robust Detail registration number or pre-completion test certificate for your specific wall or floor type — it tells you exactly what standard your home was supposed to achieve and under what construction method, which is the baseline any further testing will be measured against.
It's also worth checking whether your neighbour is experiencing the same issue from their side. A shared complaint from both households describing the same pattern of noise carries considerably more weight with a developer or warranty provider than a single, isolated report, and rules out the possibility that unusual furniture placement or a sensitivity on one side alone explains it.
If you have a snagging app tracking your other defects, log the noise issue there too, with dates and any correspondence attached, so it sits alongside your formal snagging record rather than as a separate, easily lost email thread.
How to raise it with the developer: the process
Treat a suspected sound insulation failure as a formal defect, not an informal grumble, from the outset. The process generally runs as follows:
- Written notification. Email your site manager or customer care team describing the issue, referencing your noise diary, and explicitly asking for confirmation of the construction method (Robust Detail number or PCT certificate) for your separating wall or floor.
- Initial developer response. Expect an acknowledgement and, if the developer takes it seriously, a visit from a site technical manager or NHQB-aligned customer care representative to discuss the complaint and inspect accessible areas (sockets, skirtings, loft hatches) for obvious workmanship gaps.
- Request for acoustic testing. If the initial inspection doesn't resolve it, or no visible cause is found, ask formally for an independent sound insulation test to be carried out by a UKAS-accredited acoustic testing firm, measuring against the Part E DnT,w and L'nT,w thresholds that applied when your home was built.
- Test result and remediation. If the test shows a genuine shortfall against the applicable minimum, the developer is responsible for investigating the cause and carrying out remedial work — which might mean resealing junctions, replacing an isolation strip, re-fitting a floating floor, or in more serious cases opening up and reworking the wall or floor build-up.
- Escalation if refused. If the developer disputes the finding or refuses to act, escalate via your structural warranty provider (NHBC, LABC, Premier Guarantee or similar), the New Homes Quality Board if your purchase is covered by the New Homes Quality Code, or ultimately the relevant building control body if it's a regulatory compliance question rather than a warranty one.
| Who pays for testing | When this applies |
|---|---|
| Developer | If your plot was never individually tested and reasonable evidence suggests a possible failure — most developers will commission a test rather than risk a warranty dispute escalating |
| You, reimbursed if failure confirmed | Some developers ask you to commission an independent test first, agreeing to reimburse costs if a genuine shortfall is found — get this agreement in writing before booking |
| You, not reimbursed | If a test confirms the wall meets Part E minimums — i.e. you're hearing compliant, if unwelcome, everyday noise |
Keep every piece of correspondence. If this ends up going to the New Homes Ombudsman Service or a warranty claim, a clear paper trail showing you raised it promptly, provided evidence, and gave the developer reasonable opportunity to investigate will matter.
Flats vs houses: why the acoustic picture differs
The nature of likely sound issues, and the standards that apply, differ meaningfully between house types.
Flats and apartments
In a block of flats, you potentially face both airborne transfer through separating walls and impact transfer through separating floors from the flat above — footsteps, dropped items, dragged furniture. Impact sound is generally the more common and more intrusive complaint in flats, because it's harder to fully isolate a floating floor build-up than it is to get a masonry or timber-frame party wall right, and because upper-floor residents' daily habits (hard flooring instead of carpet, for instance) directly affect what transmits downstream. If your lease or management company's rules specify flooring requirements for upper flats — commonly a minimum carpet/underlay specification or an acoustic-rated flooring requirement for any hard flooring — a neighbour fitting non-compliant hard flooring is a lease enforcement issue for the managing agent, separate from any construction-level Part E question about the floor build-up itself.
Houses (semi-detached and terraced)
In houses, the main concern is airborne transfer through the party wall, plus the loft void risk mentioned earlier where sound can travel over the top of a party wall through a shared roof space if the barrier wasn't built up correctly to meet the roof covering. End-of-terrace and semi-detached houses typically have only one party wall to worry about; mid-terrace houses have two, which doubles the number of potential junctions and workmanship opportunities for a gap to be missed.
If you're buying a flat and sound insulation is a significant concern for you, it's worth asking at reservation stage (before exchange) what floor construction is specified, whether it's a Robust Detail floor type, and what flooring restrictions apply to units above yours — this is far easier to establish before you commit than to unpick after you've moved in and discovered a noisy neighbour above with hardwood flooring and no rug in sight.
Warranty cover and timing: does it matter when you raise it?
Most new build homes come with a 10-year structural warranty (NHBC Buildmark, LABC, Premier Guarantee or similar), but the detailed protection differs significantly between the first two years and the remaining period, and this matters a great deal for a sound insulation complaint.
| Period | Typical cover | Relevance to sound insulation |
|---|---|---|
| Defects/Rectification period (usually first 24 months) | Developer is contractually obliged to fix defects reported, including workmanship issues, under the builder's own warranty obligations and the New Homes Quality Code where it applies | This is your strongest window — a sound insulation shortfall traced to poor workmanship is squarely a defect the developer should remediate at no cost to you |
| Years 3–10 (structural warranty) | Cover narrows to significant structural defects affecting load-bearing elements, weatherproofing and similar; most warranty providers do not cover general snagging or acoustic performance in this period | A sound insulation failure is unlikely to be covered once you're past the initial defects period unless it can be framed as a structural defect, which is a high bar |
If you suspect a sound insulation problem, raise it as early as possible — ideally within the first weeks of noticing it and certainly well within your defects period — because your contractual leverage to get it fixed free of charge is dramatically stronger in that window than later.
This is also why a pre-completion "snagging survey" focused purely on visible cosmetic issues can miss the acoustic question entirely — you often can't properly assess sound transfer until you and your neighbour are both living in the properties with normal furniture, routines and background noise, which is one of several reasons a second check closer to the end of your defects period is worthwhile. If you're coming up to that point, it's worth reading about what to check before your warranty expires and making sure any lingering acoustic concern is formally logged before the window closes, even if testing hasn't happened yet.
Also check whether your purchase is covered by the New Homes Quality Code, which gives you access to the independent New Homes Ombudsman Service if the developer's own resolution process stalls — this sits alongside, not instead of, your structural warranty provider's complaints process.
What realistic remediation looks like
If a test confirms a genuine shortfall, it's worth understanding what fixing it actually involves, so you can judge whether a developer's proposed remedy is adequate or token.
- Minor sealing works. If the cause is identified as gaps at junctions, missing acoustic sealant, or a bridged service penetration, remediation can be relatively quick — resealing, replacing a fire/acoustic-rated socket back box, or adding missing insulation at a loft void junction. This is the best-case scenario and usually causes minimal disruption.
- Floating floor rework. In flats, if the impact failure traces to a crushed or missing isolation strip or poorly laid floating floor, remediation may mean lifting the existing floor finish, correcting the isolation layer, and relaying — disruptive, but contained to one room or area at a time.
- Partial wall rebuild. If the cavity fill is wrong or a Robust Detail wasn't built as specified at a structural level, remediation can mean opening up plasterboard, correcting insulation within the cavity, and resealing — a bigger job, usually requiring you to vacate the affected room temporarily.
- Retest after works. Any competent developer should retest after remedial works to confirm the fix actually brought the wall or floor above the Part E minimum — don't accept "we've done some work" as closure without a follow-up test confirming compliance.
Be realistic about ceiling: remediation targets getting the wall or floor back up to the Part E minimum it was supposed to achieve, not to some higher bespoke acoustic standard. If you want meaningfully better sound insulation than the regulatory minimum — which some buyers do, particularly in flats with young families above or below — that's typically a self-funded upgrade (secondary glazing-style acoustic panels, additional resilient underlay, soft furnishings) rather than something you can compel a developer to provide once the legal minimum has been met.
Checking this before you buy, not just after
If you're still at viewing or reservation stage on another plot, or buying off-plan, there's a reasonable amount you can find out before you're committed that will save you this whole process later.
- Ask directly about construction method. Ask the sales team whether party walls/floors are built to Robust Details or verified by pre-completion testing, and ask them to point you to the specific detail type if they can — a sales team that doesn't know is a sign the information wasn't front-of-mind during build, though it doesn't necessarily mean anything is wrong.
- Visit at a realistic time. If you can arrange a visit to a similar, already-occupied plot on the same development (or a sister development by the same builder using the same house type), go at a time when neighbours are likely to be home and generating normal noise, rather than only during a quiet weekday viewing slot.
- Check the house type and position. Mid-terrace plots with two party walls carry more risk than end-of-terrace or detached. Top-floor flats avoid the impact-from-above problem entirely but may face it from below if the building has commercial space; middle-floor flats face it both ways.
- Review the development's HBF star rating and recent buyer feedback for recurring acoustic complaints — a pattern across multiple reviews is a stronger signal than any single comment. The HBF star rating comparison guide explains how to read this kind of feedback properly.
- Ask about flooring restrictions for flats in the lease, and whether they're actively enforced by the managing agent — a restriction on paper that nobody checks is of limited practical value.
None of this guarantees a silent home — no viewing exercise can replace actually living somewhere for a few months — but it shifts the odds in your favour and gives you a documented basis for raising concerns early if problems do emerge after you move in.
If you're weighing up a specific development against alternatives partly on this basis, the site's compare tool lets you look at multiple developments side by side, and the developments directory includes build specification details where developers have provided them.
Frequently Asked Questions
Is it normal to hear your neighbour's TV in a new build?
Hearing a faint, muffled presence of a TV — mostly bass, indistinct dialogue — through a party wall is generally within expected limits. Hearing dialogue clearly enough to follow the programme at normal volume suggests the wall may not be performing to the Part E minimum and is worth investigating.
What is a Robust Detail and why does it matter for my complaint?
A Robust Detail is a specific, pre-tested wall or floor construction registered with Robust Details Limited that's deemed to meet Part E without individual on-site testing, provided it's built exactly to specification. If your home used one, a sound complaint is really a question of whether the detail was built correctly — a workmanship snagging issue for the developer to investigate.
How do I find out if my wall was tested or built to a Robust Detail?
Ask your developer's customer care team in writing for either the Robust Detail registration number for your plot's separating wall/floor, or the pre-completion test certificate if your plot (or its construction type sample) was individually tested. This information should exist in the development's building control records.
Who pays for a sound insulation test if I request one?
This varies by developer. Some will commission and pay for testing themselves if you present a credible, documented complaint. Others ask you to commission an independent UKAS-accredited test first and agree to reimburse you if a shortfall is confirmed — always get the payment arrangement agreed in writing before booking a test.
What Part E figures should my new build wall or floor meet?
As of 2026, typical minimums under Approved Document E are broadly around 45 dB DnT,w for airborne sound and around 62 dB L'nT,w for impact sound through separating floors, but always check the specific Approved Document E edition and any amendments that applied when your development received building control approval, as figures and testing methodologies can change between editions.
Can I claim on my NHBC or warranty if the wall fails a sound test?
A confirmed Part E shortfall within your developer's defects/rectification period (typically the first two years) is normally the developer's responsibility to fix directly, separate from a structural warranty claim. Structural warranties (years 3–10) generally don't cover general sound insulation performance, so acting early matters.
My neighbour is just loud — is that a construction defect?
No. If the wall meets Part E but your neighbour's lifestyle (loud music, frequent parties, heavy-footed children) still bothers you, that's a behavioural and, for flats, potentially a lease-covenant matter for the managing agent, not a building defect the developer is responsible for.
Does carpet or rug placement affect impact sound test results?
Yes, but typically only final hard-floor-finish impact performance in the flat generating the noise, not the base floor construction's compliance test, which is usually conducted on the structural floor build-up before final floor finishes are laid. A flat above fitting hard flooring without adequate acoustic underlay can still create a nuisance even where the base floor construction is compliant — which is why lease flooring restrictions exist separately from Part E.
Next steps
If you're currently weighing up whether a noise issue in your new home is worth pursuing, or you're still house-hunting and want to factor acoustic performance into your decision, these tools can help:
- Use the tools section to find snagging checklists and guidance documents that cover acoustic checks alongside the visible defects most buyers focus on.
- Browse the developments directory to compare build specifications, house types and plot layouts (end-of-terrace vs mid-terrace, top-floor vs middle-floor flats) before you commit.
- Check builder track records in the builders directory, including star ratings and customer feedback patterns that can flag recurring quality issues on specific developments.
- Search live listings in properties and filter by house type if avoiding a mid-terrace or double-party-wall position is a priority for you.
- Use the map tool to understand a development's layout and which plots back onto commercial units, roads, or have more or fewer shared walls.
- If you're deciding between two or more specific developments, the compare tool lets you line up specification details, incentives and reviews side by side.
And if you've already identified a likely acoustic failure in your current home, prioritise getting it logged formally and in writing with your developer as soon as possible — your contractual position is strongest within the defects/rectification period, and a documented noise diary plus a request for your wall or floor's Robust Detail number or test certificate is the single most effective first step toward getting it properly investigated.