Quick guide to sound insulation for floors



Many flats aren’t new buildings; they used to be large houses, offices, even factories.  However, they all need to comply with the Building Regulations.

This sometimes means extra improvements are needed to make sure the building is suitable for modern residential use.

Thermal Economics is well known in the construction industry for our IsoRubber range of sound insulation for floors.  In writing this guide, we hope that you will be better informed of the sound performance requirements in the Building Regulations, and that you’ll find it easier to select the best sound insulation product for you.

Building Regulations and sound performance

The Building Regulations are complicated by the sheer volume of documents and amendments; there is no one publication which explains everything, and there is not even one legislative document which covers all of the requirements.  So, if there are no ‘Building Regulations’, then what are the Building Regulations?

The Building Regulations have a very real power, which is derived from The Building Act 1984; which allows the Government to make and enforce regulations with respect to the design and construction of buildings by statutory instruments, and also to publish ‘approved documents’ which give practical guidance on achieving the requirements.

Despite the frequent amendments to the Building Regulations, the sound performance requirements are largely unchanged since 2010; so the only statutory instrument that needs our attention is: SI 2010/2214 The Building Regulations 2010

Building flats – Building Regulations

Paragraph E1 of Schedule 1 requires that flats should be designed and constructed in such a way to provide “reasonable resistance to sound” from other parts of the same building and from neighbouring buildings.  Or, in other words, the separating building elements between flats must have sound insulation!

Regulation 41 in Part 9 also gives a requirement for sound testing to demonstrate the effectiveness of the sound insulation.  But this still doesn’t explain how much insulation is required or even what the criteria for sound insulation testing are.

Approved Document E

Officially, as an approved document, Approved Document E is guidance only.  However, it is a primary reference document for Building Control Officers and de facto minimum standards.

Moreover, Approved Document E provides some specific requirements for proving compliance with the Building Regulations; which for material change of use in flats is:

Airborne sound insulation
DnT,w + Ctr
(dB)
Impact sound insulation
LnT,w
(dB)
Walls ≥ 43
Floors & Stairs ≥ 43 ≤ 64

 

Material change of use includes where a house is being converted into flats or a care home with individual dwellings within the same building.

Noise transmission is divided into two separate categories: airborne and impact; although impact noise transmission is only applicable to floors and stairs.

Airborne noise can be described as the passage of sound through the air and materials by sound waves; such as radios, televisions, people talking, &c.  However, impact noise sources are always footfall on floor surfaces or similar.

Sound Insulation in flats – Decibels and Sound Pressure Levels

The units for sound transmission are decibels (dB), which are a measure of how loud a noise is.  Although the loudness of how we perceive noise also depends on pitch as well as it’s volume.

We perceive LOWER frequencies to be louder than HIGHER frequencies, even when both sounds have the same amplitude.

A sound pressure level is a measured level of noise in the room measured.  Sound is measured at intervals of one-third octaves to measure a range of frequencies, and averaged across a weighted standardised curve to compensate for the perceived difference in loudness between frequencies.

This is shown by the subscript: “nT,w”.

Measuring Airborne Sound

Airborne noise is measured by adding a noise source with known frequencies and amplitudes to a room (usually via a spherical or hemi-spherical speaker), and measuring the difference between the weighted standardised sound pressure levels in the adjoining flat with and without the noise source.

The sum of the difference between sound pressure levels and a spectral adaption term must be at least 43 dB for the floor to comply with Approved Document E.

Measuring Impact Sound

Impact noise is measured by adding a noise source with a known frequency via a tapping machine to simulate footfall, then the weighted standardised sound pressure level is measured in the room below.

The difference is not important, but it is important that the noise does not exceed a maximum threshold.  Therefore, the floor satisfied Approved Document E if the tapping machine does not raise the sound pressure level above 64 dB.

Insulating floors in flats

In short, a separating floor should absorb airborne noise transmission and isolate against impact noise with a resilient layer.  A good construction detail will also design out sound paths that bypass the sound insulation; leading to unwanted, flanking sound transmission.

However, the first thing that must be established is whether the floor construction is timber (also includes I-beams, web joists and other steel joists); or concrete (including in-situ cast, pre-cast concrete planks and composite profiled decks).

Timber floors in flats

Thermal Economics standard refurbishment solution for joisted floors is now the IsoSonic Dekfloor system.

Where possible, lath-and-plaster ceilings should be retained subject to achieving the correct fire resistance; otherwise replaced with two layers of gypsum plasterboard on either our IsoSonic Ceiling Hangers / Brackets or resilient bars to reduce flanking sound transmission.  Key requirements for the ceiling are:

  • 30 minutes resistance to fire*
  • Staggered joints (for plasterboard)
  • surface mass of 20 kg∙m‑2

* Only applicable for flat conversions with maximum of three storeys, and adequate protection of escape routes.  Seek specialist advice on compliance with Part B.

One hundred millimetres (minimum) of mineral wool (with minimum density of 10 kg∙m‑3) installed between joists to absorb airborne noise transmission.

Impact noise is isolated by replacing the timber deck with IsoSonic Dek 30, which incorporates our IsoRubber resilient layer already bonded to the deck, installed as a direct-to-joist treatment.  Flanking sound transmission is also isolated with the use of our IsoEdge 6 / 75 strip at wall perimeters.

Concrete Floors in flats

Thermal Economics standard refurbishment solution for concrete floors is IsoRubber Top.

Concrete floors are usually easier to upgrade, because providing the concrete slab has a surface mass of 200 kg∙m‑2 there is no requirement to install any other additional absorbent material.  However, a resilient layer of 3 mm IsoRubber Top should be glued to the substrate with IsoBond to isolate against impact noise transmission.

A suspended ceiling should be installed on timber battens using one of our IsoSonic Ceiling Hangers / Brackets or on resilient bars.  However, the ceiling only needs to be a single layer of gypsum plasterboard with a minimum surface mass of 10 kg∙m‑2.

Technical advice for sound insulation in flats

Although this quick guide should be sufficient to help you start designing your separating floor construction, you may need some further help and information.

Thermal Economics has a knowledgeable technical department who can help you to make the right decisions when specifying products for your separating floor; and who can be contacted for advice either by:

  • Calling 01582 544255
  • E-mailing [email protected]
  • Using our free LiveChat service on our website. Just click the speech bubble!