How much does sound insulation testing cost? A plain guide.

Sound insulation testing is usually priced per test, per set or per visit. We price per visit, as a fixed fee from £675 + VAT. That covers the tests agreed for the visit, the calibrated equipment, and certificates suitable for building control. What decides your final sound insulation testing cost is how many tests the development needs, how many visits it takes to reach them, and whether any of them fail.

This note sets out how the number of tests is worked out, why conversions and new build behave differently, where Robust Details fits, and what a failure adds to the bill. If you only need the pass values, our Approved Document E explainer has them. Approved Document E applies in England, and Wales has its own version. Scotland and Northern Ireland set their own requirements, so the sample there follows those rules rather than this note; the fee is fixed in the same way.

How sound insulation testing is priced

Per-test and per-set rates can look small until they are multiplied by the sample. Our visit fee covers every test the sample needs on that day, fixed and agreed before anything is booked. Whichever basis is used, the cost is mostly engineer time on site and time writing up, set by the number of tests and how quickly the rooms can be worked through.

A fixed fee from £675 + VAT covers:

• The site visit, with the tests agreed at quote stage
• Airborne tests of separating walls and floors, and impact tests of separating floors, to the standard field test methods
• Class 1 sound level meters holding current traceable laboratory calibration certificates, field-checked before and after testing
• Results checked against the Approved Document E standards on site, so you know where you stand before we leave
• Certificates suitable for building control within five working days of the test
• Advice on the sample to agree with building control, so you do not pay for tests Approved Document E does not ask for

What it does not depend on is where the site is. The fee is fixed and the programme runs the same wherever the building stands.

What a set of tests is

Approved Document E does not ask for every wall and floor to be tested. It asks for a sample, organised in sets. A set is a small group of individual tests taken together, and what it contains depends on what separates the homes.

The difference between airborne and impact testing is explained on our sound insulation testing page. For pricing, what matters is simple: walls need airborne tests only, and floors need both. That is why a block of flats takes far longer to test than a terrace with the same number of homes.

How many tests your development needs

The sampling rule is at least one set of tests for every ten houses, flats or rooms for residential purposes in each group or sub-group of construction. Approved Document E sorts the work into groups (houses, flats, and rooms for residential purposes) and then into sub-groups by how they are built: the separating wall, the separating floor and the flanking details around them. Change the construction and you start a new sub-group, with a sample of its own.

Take a block of 20 new-build flats, all built the same way, with separating walls and floors. That is two sets, so twelve individual tests. Now add four flats formed in a converted building at the back of the site. They are a different construction, so they need a set of their own, even though there are only four of them. A handful of plots in an unusual construction can add more testing than people expect.

Building control decides the final sample for your site, and it is worth agreeing it in writing before anything is booked. A planning condition or a BREEAM or similar sustainability target can also ask for more than Part E does, or set a higher standard to meet. Send the decision notice and any sustainability brief with your enquiry and we will price against what they actually ask for.

What moves the sound insulation testing cost

• The number of sets. Every set adds tests, and every test adds time on site.
• Houses or flats. A house set is two tests; a flat set with walls and floors is six. The same number of plots can mean a very different day.
• The number of visits. Phased completions often mean the full sample cannot be reached in one visit. A block finished weeks after the last one is usually its own visit.
• Readiness on the day. Rooms that are not finished cannot be tested, and coming back is a second visit.
• Retests. An element that fails has to be tested again once it is fixed, which normally means another visit.

The first three are set at quote stage from your plot schedule and programme, and go into the fixed fee. The last two are in your hands, and most of the rest of this note is about avoiding them.

New build versus conversion

New build and conversions are both subject to pre-completion testing, though new-build houses and flats can use Robust Details instead. Dwellings formed by a material change of use, which is what most conversions are, have slightly less demanding performance standards, set out in our Approved Document E explainer. That margin is rarely enough to make up for the building a conversion starts with.

Joists that run across the separating line, old chimney breasts, original walls that continue past the new floor, floors bridged at the edges: these are flanking paths, routes for sound around the separating element rather than through it. They are much harder to control than in a building designed for separation from the start. Conversions cannot use Robust Details either, so a conversion that creates separating walls or floors relies on pre-completion testing.

New build is more predictable when the design is right, but it fails in the same places: junctions, service penetrations and isolating layers bridged during the build. Whether it is new build or a conversion sets the target. The workmanship sets the result.

Robust Details: the alternative to testing

Robust Details is a scheme of pre-approved separating wall and floor constructions for new-build houses and flats. Plots registered with the scheme and notified to building control before building work starts on site, and built strictly to a listed detail, do not need pre-completion testing. Each plot has to be registered with the scheme, and the specified products are not always the cheapest way to build.

Whether it saves money depends on the job. It suits repeated, simple house types built to a standard detail. It does not suit a design that departs from a listed detail, which cannot be registered in the first place, and it suits less well where substitutions are likely on site, because a departure from the listed detail puts the plot back into testing, usually late. Any plot that is not registered, conversions included, is tested in the normal way, so mixed sites often end up using both.

What a failed test costs

The fee for the test is the smallest part of a failure.

The real cost is finding the cause, carrying out the remedial work, the return visit to retest, and the handover that waits for all three. If the cause is a detail repeated through the block, the fix is repeated too, including on plots that were never tested. Approved Document E also expects the rate of testing to go up after a failure, until building control is satisfied the problem has been put right.

Many failures come through flanking paths rather than a weak separating element, so the money is saved by finding the actual path on site before any remedial work starts. Our Approved Document E explainer sets out the usual causes.

How to avoid a failed sound test

• Have the separating constructions and their junctions reviewed at design stage, before a weak detail is drawn into every plot.
• Look at the first plot before it is closed up. Resilient layers, cavity insulation, edge strips and service penetrations are easy to check before the plasterboard goes on and impossible after.
• Brief the trades who follow. Many failures are built in by someone fixing something else: a socket back to back, a downlight cut through a ceiling, a skirting fixed through a floating floor.
• Test the first completed plots early, so a problem shows up once rather than across the whole block.
• Have the rooms ready on the day. What they need is set out on our sound insulation testing page, and we run through it with your site manager when the visit is booked. A site that follows it rarely needs a return visit for readiness.

When to book

Book as soon as the handover date is known, and test close to completion but before carpets and other soft floor coverings go down. Test too early and rooms can fail that the finished building would pass, which means a second visit. Test too late and carpets have to come up for impact tests, or handover waits on a test that could have been done sooner.

On a phased site, plan the visits around the phasing rather than leaving everything to the end. Testing the first block as soon as it is finished is cheap protection against repeating a mistake through the rest. Short-notice visits are often possible, and certificates follow within five working days of the test.

For a fixed fee, send the postcode, the number of plots, the construction types and your handover date through the quote form. Quotes come back within 10 minutes on average, and we will set out the number of sets the sample is likely to need before you commit to anything.