Treat the acoustic comfort of floors
Batirama.com 05/20/20080
Traditional wooden floors are not renowned for their acoustic performance. Simple and inexpensive techniques make it possible to correct one of the weaknesses of these systems: the absence of mass.
A traditional wooden floor has never given good results acoustically, both in terms of airborne noise and impact noise. These are the easiest to treat, through the floor covering, textile or rigid by interposing a resilient acoustic underlay. When the floor is lined on the underside of a suspended ceiling, the interposition of fibrous insulation attenuates transmission noise, but not much impact noise. The ideal is obtained with floating screeds.
Stay pragmatic
Acoustic improvement between two floor levels is complex to deal with. Airborne noise can be treated in the same way as in partitions, based on plasterboard on a metal frame and insulation, but impact noise is very little attenuated by this type of treatment. The ideal is to be able to treat them at the source, which is necessary to intervene at the higher level. In this case, there are many thin underlays for tiles, floating floors and laminates. Unlike airborne noise, it is the texture of the floor covering that makes the difference: a parquet floor is bad with respect to impact noise, while a simple carpet attenuates the main effects.
Source: batirama.com / P.Valaire
The acoustic underlays must be implemented between the floor covering and the floor.
These underlays reduce impact noise, unless the covering itself is sufficiently efficient to be able to do without it (carpets, certain PVCs and linoleums). They are generally made of polyethylene foam, wood fibers or cork. Their composition must make it possible to resist settling while maintaining their acoustic qualities. The factory-bonded underlay on the underside of the covering is even more efficient. Comparative tests show that it saves 4 dB compared to the same product used on an underlay in rolls and laid “loose”. In addition, installation is faster and easier. Full bonding of the floor covering with acoustic underlay is even better. This technique is nevertheless expensive, because of the slowness of the installation and the high price of the glues, specially formulated not to bring humidity to the parquet or the laminate.
Depending on their composition, some floor coverings may or may not require an acoustic underlay.
Textile coverings have to compete with hard floors, which are more "in tune with the times", yet they are very efficient in terms of attenuating impact noise.
TO REMEMBER :
Interests: Limited investment; Ease of implementation; effectiveness against impact noise
Limits: Variable qualities from one product to another; No effect on airborne noise
When the ceiling height is high, the realization of a suspended ceiling in plasterboard on a metal frame proves to be an interesting solution.
A suspended ceiling makes it possible to incorporate a significant thickness of fibrous insulation, which limits the transmission of airborne noise. The use of anti-vibration hangers, which are more expensive than conventional hangers, further improves the result, including with respect to impact noise. Better still, the implementation of a self-supporting ceiling represents the ideal solution, by total absence of mechanical connections. This technique consists of carrying metal profiles from partition to partition, without any mechanical link with the original ceiling. In the attic of old houses, the space between the floor and the ceiling of the lower level can be effectively filled with loose fill insulation. It is an effective way to limit the transmission of airborne noise, without having to add thickness to an attic floor, a place often already limited in available height.
In new construction, the plenum of a wooden floor can be effectively filled with insulation. On this site of a log house, the company insulates the plenum using wood shavings generated by the site.
In new construction as in renovation, the implementation of a suspended ceiling incorporating acoustic insulation is a good response to airborne noise.
TO REMEMBER :
Advantages: Effective for the reduction of airborne noise
Limitations: Require available volume; Limited effect on impact noise
The floating screed solves the problem of airborne noise and impact noise in a single operation.
Two techniques are possible: the dry screed and the liquid screed, the aim being to separate the floor from the supporting structure, with the interposition of an acoustic insulation dense enough not to generate settlements over time. Dry screeds come in the form of special plasterboards which incorporate insulation or an insulating underlayer applied in bulk on the underside. This solution has several advantages for wooden floors: no water supply, no drying time, clean worksite, limited overloads and possibility of horizontalizing a sloping or sagging floor. Liquid screeds are reserved for floors capable of supporting a certain overload. The organization of the site also influences the technical choice. A masonry company already present on the site and equipped with a cement mixer tends to turn to the liquid screed, a plasterer automatically chooses the dry way.
Liquid screeds should be reserved for floors capable of supporting a certain overload. Under certain conditions, they allow the incorporation of fluids, including underfloor heating systems.
The dry screed provides a dual response to airborne noise and impact noise. In addition, the installation is fast, without drying time, it also allows to find the horizontality on a deformed floor.
TO REMEMBER :
Benefits: Effective in reducing airborne and impact noise; Leaves the underside of the floor visible; Levels a sloping floor
Limits: high cost; Reduction of the living height (attic constraints); Imposes to take back the plinths, height of doors... To be reserved for heavy renovations
In renovation, the composite wood/concrete floor is used to reinforce existing wooden floors, particularly when you want to keep an exposed underside.
A new, thin concrete or resin mortar floor is poured over the old preserved floor. The connection between the two materials is made via connectors (concrete), or notches made before pouring into the old floor (resin mortar). This technique increases the resistance to the loads of the floor, it ensures horizontality, and brings by its mass a high performance with respect to the reduction of airborne noise. The same principle with the same advantages can be applied to new construction, with the Sylvabat system (protected by a patent filed by Cosylva) or Lignadal (under Archipente licence). This is the combination of a wooden pre-slab and a concrete compression slab, linked by wooden connectors, the wooden underside remaining visible for aesthetic purposes.
Thanks to the implementation of a collaborating floor, this old floor, located in a castle, will be able to support the loads planned on the upper level within the framework of the development of a conference room. This technique makes it possible to preserve the underside, but also to find the lost horizontality.
TO REMEMBER :
Interests: Attenuation of airborne noise; Mechanical resistance ; Restoration of horizontality (old floor)
Limits: High cost (compared to a basic wood floor); heavy work; Drying time to respect; To be reserved for major renovations
“Adapt to the context”
We do a lot of timber frame extensions and elevations. The upper levels are often those of the bedrooms and we are careful to deal with impact noise. The current trend being for parquet or loose laid laminate, we advise the customer to insert an acoustic underlay between the floor and the floor covering. For practical reasons, we rarely leave the underside visible, and produce plasterboard ceilings. It is then easy to fill the plenum with glass wool, which greatly reduces the transmission of airborne noise.
* company FA Décors (94 Limeil Brévannes)
Pascal Ozouf*
“Seek a realistic result”
There are enough simple and inexpensive solutions to improve the acoustic performance of a wooden floor. These applications concern the habitat, and that we are not aiming for absolute silence. The contractor who intervenes on such a building must use common materials, but of quality: mineral wool, acoustic underlays. Precision and quality of implementation are priorities. When it is technically and financially possible, the installation of a floating screed allows high performance. Note that the treatment of impact noise is much more effective when it can be done at the source.
*acoustic engineer, BPB Placo
"Floor plates laid on insulation"
We build cabins. On the first floor, all the floors are made of wood, an aesthetic technique, but with poor acoustic performance. We circumvent the problem by implementing a floating screed on the floor of the first level. An 18 mm thick floor in Northern wood is nailed to the joists. On this floor are laid free Fermacell floor plates. Composed of plaster and cellulose fibres, these slabs have a 30 mm thick rock wool on the underside, dense enough not to compress under the weight of the slabs. This "floating" installation reduces the transmission of impact noise. The high density of the Fermacell sheet (1200 kg/m3), linked to the presence of rock wool, also helps to limit the transmission of airborne noise.
* chalet builder (05 Briançon)
ADDRESSES
• CIDB: www.infobruit.org/FR/info/00
• SFA: www.sfa.asso.fr/pres.htlm
• CSTB: www.cstb.fr
Book on the acoustic behavior of old floors. Brief history of construction techniques to justify the choice of frames tested in the laboratory. Catalog of possible solutions, summary produced globally for in situ measurements and by type of process for laboratory measurements. 01 64 68 82 82
Some manufacturer guides
• Isover: catalog of insulation products and solutions
• Isover: building acoustics guide
• Knauf: the global offer
• BPB Placo: general catalog
• Lafarge: guide to acoustic solutions in housing
