Posted: 2nd November 2021

How to improve sound insulation for a timber joist floor

Effective sound insulation should be pre-planned into any new development as new homes are subject to Building Regulations Approved Document E, which aims to protect residents from noise in other rooms or adjoining properties.

If you’re seeking effective ways to insulate existing timber floors when forming new residential flats in an existing building, there are two types of sound transmission you should consider:

1) Impact sound is created when objects come into contact with a wooden floor, imparting energy into the structure that travels through the building.  A common example of impact noise is footsteps, but may also occur when objects are dropped onto the floor.

2) Airborne sound is caused by many different sources in a dwelling, such as voices, music, pets, or the television.

Compared to concrete floors, timber joist floors pose a very different problem in terms of sound transmission.  Concrete floors will generally provide a good level of airborne sound insulation and only require a resilient layer above to control impact sound transmission.  Controlling impact and airborne noise is challenging because wooden floors lack the structural mass of concrete floors, requiring additional mass layers and, most importantly, introducing separation into the structure.


Effective strategies to improve sound insulation and noise control

1) Improve the mass of the floor and incorporate separation

Improving the mass of a timber joist floor can be achieved by installing high density products, such as a secondary plasterboard ceiling to the underside, if access is possible.  This eliminates the need for more expensive acoustic products and can achieve excellent airborne sound insulation.

Where this mass layer can be acoustically separated from the existing structure, for example by using independent timber joists, acoustic hangers, or resilient bars, then there is a significant jump in the benefit achieved compared to simply adding additional layers of plasterboard to the existing ceiling.


2) Include a resilient layer

Including a resilient layer will significantly improve impact sound insulation through the floor.  This can be achieved with a platform floor on a resilient layer such as dense mineral wool or proprietary acoustic foam, or through specialist acoustic overlay boards where chipboard or MDF is bonded to the foam layer.

High-quality underlay, overlaid with carpet, is one of the cheapest and easiest ways to retrospectively improve impact sound transmission of a separating floor; however, carpet/underlay must be lifted when undertaking impact pre-completion sound insulation tests for Approved Document E and therefore cannot be accounted for when designing the appropriate floor construction.


3) Install acoustic insulation

All successful timber joist separating floor constructions will incorporate mineral wool insulation within the ceiling void or between timber joists to reduce the transmission of sound between rooms.

It is important the insulation is fibrous mineral wool or Rockwool type rather than PIR foam and similar thermal insulation, which offers almost no benefit for sound insulation.


Preliminary sound insulation tests

Before carrying out any work to improve the sound insulation of existing timber joist floors, it is often best to carry out preliminary sound insulation tests on the existing structure.  This will show how well the existing floor is performing.

It might be that the existing floor already achieves the requirements of Approved Document E.  In which case, you don’t need to carry out any work and can save yourself from unnecessary expense.  On the other hand, the preliminary tests can identify the extent of any shortfall, allowing experienced acoustic consultants to design appropriate improvement works.  This will make sure that the final tests pass first time, again saving you money in the long run.


Contact ACA Acoustics for professional sound insulation testing

In new or conversion residential houses or apartments, sound insulation testing is a requirement to comply with Approved Document E of The Building Regulations.

At ACA Acoustics, we offer a complete service from reviewing initial plans and designs, carrying out preliminary tests on existing separating walls and floors, undertaking site inspections during the construction works, through to formal pre-completion sound insulation tests for Building Regulations.  We are fully accredited to undertake sound insulation testing on completed properties. To find out more, please get in touch.


Image Source: Pexels

Posted By:ACA Acoustics