Soundproofing Floors

Soundproofing Floors

Sound is an issue that affects most of us at some point even if we don’t realize it at the time. How often do you hear the noise of talking or TV from an adjacent room or some walking across the floor above? Soundproofing will greatly reduce these sounds however it must be done correctly.

We commonly come across this issue during refurbishment projects such as conversion of large houses into flats. Guidelines for reduction of sound in all types of properties (new build and conversions) are described in detail in Approved Document E of the Building Regulations. However this might not be how you like to spend your evenings reading such documents!

Sound is classified into two categories – Airborne or Impact. A simple way to determine what type of sound is affecting you is as follows:

1. If you want to stop the sound of a TV or conversation in an adjacent room then you are trying to stop airborne noise.

2. If you are trying to stop the sound of footsteps, objects being dropped or the noise of furniture being moved around then you are trying to stop impact noise.

Or a more technical explanation would be:

Airborne Sound – This occurs when a sound transfers directly from a source to the receiver. Typically this would be through small holes or openings in the construction, along ductwork, or through voids such as ceiling cavities. Airborne noises are conversation, TV noise, music, barking dogs.

Impact Sound – Impact noise is structural vibration, transmitted from a point of impact through a structure and experienced as radiated sound from a vibrating surface. This is commonly caused by an item hitting the floor, from where the impact results in vibrations being transferred through the buildings structure. The most common path for the noise is generally to the ceiling of the lower property or room. Impact noises are footsteps, dropping items on the floor, or children running.

  • a TYPICAL wooden separating floor IS constructed of timber joists and floorboards

This type of floor construction is used in most domestic properties; the typical floor construction will be plasterboard or lathe and plaster ceilings, timber floor joists and wooden floorboards or chipboard flooring over the top. Floors constructed in this way with little or no insulation and no absorbent or resilient layer on the floor will allow airborne and impact noise too easily pass between rooms from one room to another through the floor.

  • HOW WE Stop airborne sound transferring through a floor

Insulating between the floor joists with acoustic insulation will reduce airborne sound transmission through wooden floors. Building Regulations stipulates using 100mm 45kg/m³ insulation between the floor joists as part of a separating floor solution to comply with Part E. Generally we prefer an increased level of soundproofing and we recommend and install a minimum of 80/m³ acoustic insulation slab, the higher density will reduce more airborne noise. Compliance with Part E does not mean sound will not transfer between the floors. The higher density 80kg/m³ insulation slab will block and absorb more airborne noise. However we should note that acoustic insulation should not be confused with rolls of thermal insulation which are lower in density, therefore do not offer the same level of sound insulation.

An example of dense insulation slab  

When we install acoustic insulation between floor joists, we cut the slabs to size using a hand saw, cut them slightly larger than the opening so the slabs will friction fit between the floor joists, ensure the whole area is filled with insulation using any off cuts to fill any small gaps. Using acoustic insulation below the floor will reduce all types of airborne noise.

There are alternative materials available is the client does not want the hassle of lifting floorboards. An alternative material is a high density rubber mat that can be laid over the top of the floorboards to reduce airborne noise. It looks similar to carpet underlay however it is a much denser material….and more expensive!

  • Stop impact sound transferring through a floor

To effectively reduce impact sound through a floor you need to reduce the vibration caused as an item hits the floor. The level of noise that will transmit through the floor depends on the force of the impact, the vibration transmission characteristics of the floor structure and the floor covering.

There are two types of floor soundproofing solutions to reduce impact noise, acoustic matting or floating floors; both solutions will reduce impact noise transferring through wooden and concrete floor structures.

Deciding which type of flooring suits your requirements will depend on certain factors.

A. Floor finish

  • Carpet
  • Laminate
  • Tiled
  • Wooden

B. Height requirements

  • What is the height restriction?
  • What height can you raise the floor?

C. Building Regulations

  • Do you have to meet certain requirements?
  • Use acoustic matting to soundproof floors

Acoustic matting is the most common form of floor soundproofing used to reduce impact noise. These types of products are specifically designed to be used over any floor below most floor finishes including, carpet, wooden floors, laminates and tiled floors. Again similar to a carpet underlay just a denser material.

An example of acoustic underlay

NSSF7+ acoustic underlay mat

This type of flooring can be laid down quickly and easily. The mats are cut with a sharp knife, laid with joints staggered with the edges butted together. A strip of matting can be laid around the perimeter of the room if you are using carpet underlay and carpet.

If you are laying a hard floor finish over the mats you might need to use a layer of 9mm ply or equivalent over the matting to reduce movement.

Acoustic mats can be used to soundproof separating floors to meet the requirements of Approved Document E when combined with acoustic insulation and the correct ceiling construction. We will cover ceilings in another blog post.

  • Floating floors reduce high levels of impact noise

A floating floor refers to flooring that is not mechanically fixed in place with nails or screws. Floating floors are normally supplied as interlocking flooring that has a tongue and groove edge that fit together locking the floor in place, soundproof floating floors have a resilient layer bonded to the underside, this layer is to isolate the floor from the buildings structure, this isolation will reduce sound transmitting through the floor and joists into the room below.

Floating floors can be laid over wooden and concrete floors to reduce high levels of sound and to ensure new build and conversions achieve the requirements of Approved Document E. Floating flooring can be laid either directly onto the joists or over the existing floor.

Install a floating floor in rooms that require the highest level of sound isolation. Floating floors can be used in specialist applications such as recording studios to reduce vibration along the floors from one room to another.

The flooring needs be isolated from the wall to reduce “flanking” noise. Flanking noise is where the sound finds the least path of resistance and travels behind skirting and under the floor down the room below. To prevent this, flanking tape or isolation tape can be fixed between the floor and the skirting to help isolate the flooring from walls. An alternative is to seal around the perimeter of the floor with an acoustic sealant.

Watch out for our next article on soundproofing walls………