AU783624B2 - Building Construction - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

r Name of Applicant/s: Actual Inventor/s: Address for Service: Fletcher Challenge Limited Kevin James Golding and Robert Malcolm Hallows BALDWIN SHELSTON WATERS 60 MARGARET STREET SYDNEY NSW 2000 'BUILDING CONSTRUCTION' Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me/us:- File: 31165AUP00 BUILDING CONSTRUCTION

BACKGROUND

The present invention relates to improvements in and relating to building constructions and in particular to building constructions having improved sound control characteristics.

Building codes throughout the world set standards for test methods, such as the ISO Testing Standards and the American Standards Testing Methods, in respect of "airborne and impact sound". These include, by way of example, a Sound Transmission Class (STC) and Impact Insulation Class

(IIC).

To achieve, in current building constructions, the prescribed performance targets has proved to be difficult, particularly those relating to habitable spaces. A particular problem is in respect of sound transmissions performance targets for floors and the insulation of floors against impact sound, especially with hard floor coverings or light timber frame construction.

In addition to objective measurement requirements, research has shown the physiological and psychological effects on occupants of buildings of impact sound, see "Physiological Evaluation of Floor Impact Sounds in a Two- Storey House", Morikawa et al Proceedings of Pacific Timber Engineering •Conference, Rotorua, New Zealand 14-18 March 1999 (Forest Research Bulletin 212).

The applicant has in testing found the surprising benefit of using at least one layer of high density gypsum fibre board in a building construction, insofar as this has been found to provide surprising sound control characteristics.

Although the use of high density gypsum fibre board (GFB), which includes its variant known as gypsum wood fibre, has proven in trials to be surprisingly effective as sound insulation and sound control, further 0o•0 testing has indicated that new and surprising improvement in sound control and sound insulation is achieved by the creation of what may be termed intersurfacial damping, created by the contacting of at least two sheets of building materials.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved sound damping, control, and/or insulation hereinafter "sound control" by the creation of intersurfacial damping or to at least provide the public with a useful choice.

Further objects of this invention will become apparent from the following description.

SUMMARY OF THE INVENTION According to one aspect the invention provides a method of impact sound control for a building construction including the provision of intersurfacial damping (as herein defined) in a floor of the building construction by securing together of at least two sheets of material so that their respective adjacent surfaces are in contact over at least a S• 20 substantial portion of their respective surface areas and wherein at least one sheet of material is of gypsum fibreboard, gypsum wood fibre or plasterboard.

In one embodiment the method as above defined includes the provision of at least one sheet of a high density gypsum fibre board.

According to a second aspect the invention provides a building construction utilising an impact sound control method according to the method of the first aspect.

According to a still further aspect the invention provides a multi-layer assembly S• 30 of sheets of material to provide impact sound control by intersurfacial damping (as herein defined) in a floor of a building construction in which the assembly includes at least two sheets of material secured together so that there is contact between at least a substantial portion of their respective surface areas and wherein at least one of the sheets is of gypsum fibreboard, gypsum wood fibre or plasterboard.

3a Further aspects of this invention which should be considered in all its novel aspects will become apparent from the following description given by way of example of possible embodiments of the invention and in which reference is made to the accompanying drawings.

*2 *3 2 *e*e I 1 4 BRIEF DESCRIPTION OF DRAWINGS FIGURE 1: shows diagrammatically one possible floor construction according to one possible embodiment of the invention; FIGURES 2 A B C: show very diagrammatically further possible floor constructions according to further possible embodiments of the invention; FIGURE 3: FIGURE 4: shows very diagrammatically one possible wall construction according to one possible embodiment of the invention; shows very diagrammatically one possible intertenancy floor structure according to one possible embodiment of the invention; shows very diagrammatically a typical existing intertenancy floor; FIGURE 5: FIGURES 6 B: shows very diagrammatically a multi-layer system according to possible embodiments of the invention; FIGURES 7 TO 11: show graphical comparisons of the present invention according to possible embodiments with existing systems.

DESCRIPTION OF PREFERRED EMBODIMENTS In many areas of building construction there is a need to provide sound control and the laboratory rating of IIC 55 is one which has been sought to be achieved at least in New Zealand in respect of some buildings.

In some types of building constructions such as constructions including e *1 a concrete floor it may be extremely difficult to achieve any acceptable sound rating especially if the concrete is left uncarpeted in a domestic dwelling.

Impact sound transmission through floor-ceiling systems is a worldwide problem. This is especially so for systems with a hard surface finish e.g.

tiles or timber strip flooring. Building developers often struggle to meet impact transmission requirements between occupancies. The ability to improve a single number sound transmission rating by only a few points can mean the difference between the failure and success of a building construction. There is also a world-wide concern to keep the thickness of impact insulating systems small e.g. to minimise a step between hard surfaced and carpeted areas. Another concern is to reduce mass so that there is less dead load and hence lesser serviceability and structural requirements. The applicant has in experimentation found surprising benefits when multiple thin layers of a material reduced impact sound transmission significantly more than a single thicker layer of the same material. The applicant refers to this phenomenon responsible for impact sound transmission improvement in multiple layer 20 systems as "intersurfacial damping". The applicant has no definite explanation for the phenomenon and it may be that when the phenomenon is °better understood that a new term will be used to describe it. The term "intersurfacial damping" does however, appear to define the phenomenon S.succinctly in that it is the creation of an unexpected and symbiotic effect of two surfaces of material providing a better impact sound transmission characteristic than a single layer of the same thickness.

In order to achieve improved sound control the present inventors have found that sound control can be achieved by the creation of intersurfacial damping, this by providing a "sandwich" of two or more layers of suitable building materials.

More particularly, the present inventors have found that impact sound insulation may be significantly improved by providing sound damping and/or sound insulation by way of contacting the surfaces between multiple sheets of sub-flooring covering. It is believed that the intersurfacial damping/isolation across the sheets of material may be primarily due to slipping between the surfaces and/or viscous pumping of air between the surfaces. It is therefore "IV *9 6 believed that the sheets of material should not be laminated but would preferably be loose laid or may be firmly fixed at points for example screwed, nailed or spot glued together, for example at 200mm centres.

It is further believed that at least one sheet should have the following properties: thickness between about 5mm and (ii) flexural stiffness between about 1.5 gigapascals and gigapascals.

Additionally the sheet should have a suitable surface hardness and S"surface roughness.

l• **In one particular trial providing an improved sound control the 20 intersurfacial damping was provided by a 7mm 7mm thick layer of gypsum fibre board (GFB) laid under a 20mm sheet of particle board. This performed ooooo 4 to 5 dB better between 350Hz and 4000Hz than a single sheet of sheet beneath a sheet of particle board.

It is believed that the intersurfacial damping created by the positioning of the two sheets relative to each other provides a symbiotic effect, more than would have been expected from the combined characteristics of the separate sheets.

It is therefore believed that the layering of such sub-flooring covering with or without other building elements, possibly augmenting inherent characteristics, is the major reason for the improved sound control and particularly in the case of impact sound insulation.

In the selection of the most appropriate materials to use in creating the intersurfacial damping, the frequency which is sought to be controlled may be particularly relevant.

In Figure 1, by way of example only, a floor/ceiling construction, generally indicated by arrow 1, is shown with intersurfacial damping provided across the floor 2 by positioning adjacent one another a sheet of particle board 3 next to a sheet of gypsum fibre board 4. The sheets 3 and 4 may be screwed, nailed or glued together in creating he necessary boundary. It is believed that all-over gluing of the adjacent sheet surfaces should be avoided.

This floor 2 is shown laid across timber joists 5 and would be intended to deal with sound control issues.

This construction of Figure 1 is given merely by way of example and in the case of a concrete floor again at least one layer of gypsum fibre board or gypsum wood fibre or similar may be positioned next to the concrete, in forming part of the floor construction and in creating the intersurfacial damping, using spot glue, nail or other spaced mechanical fasteners.

In further embodiments of the invention it is envisaged that multiple **intersurfacial damping layers may be created by the use of several layers of one or more materials. It is envisaged that in some embodiments layers of the same material may be used adjacent one another so that for example two oole• layers of gypsum fibre board may be positioned together.

Referring now to Figures 2A, B and C there are shown embodiments of this invention in its application to floor systems although shown very diagrammatically.

In Figure 2A a finishing surface 6 is shown provided above in this example, a layer of gypsum fibre board 7 laid over a sheet of flooring board material 8 so that the sheets 7 and 8 provide for the intersurfacial damping layers.

In Figure 2B the layers 7 and 8 are transposed so that the gypsum fibre board or the like is provided as the lower layer.

In Figure 2C, the same reference numerals being used where appropriate, multiple layers 7 of gypsum fibre board are shown provided above a flooring board material 8. It will be appreciated that although only 8 three layers 7 are shown, any number of layers may be used as appropriate, the adjacent sheets of material 7 and 8 providing for the intersurfacial damping.

Referring to Figure 3 a single frame or double frame wall which will have a mirror image on the other side or other lining system is shown by way of example with a finishing board 9, which itself could be GFB, and one or more layers 10, two layers being shown, of gypsum fibre board or the like and a wallboard material 11, again possibly GFB, so that the layers 9, 10 and 11 provide for the intersurfacial damping.

Referring now to Figure 4 the present invention is shown in its application to an intertenancy floor in a building. A surface finishing layer or system 12 is shown provided over one or more layers 13 of gypsum fibre board or the like (only one layer being shown) and above a flooring board material 14, the sheets 13 and 14 providing for the intersurfacial damping.

*•Below the floor a ceiling board arrangement 15 is supported on clips 16.

In contrast, as shown in Figure 5, a typical existing intertenancy floor would merely have the provision of a surface finishing layer or system 12 provided over the flooring board 14.

V In Figure 6A a loose laid layer 16 is provided over a further flooring layer 17 and above a concrete floor 18.

In Figure 6B multiple layers 16 of the gypsum fibre board or the like are provided.

In all possible embodiments of the invention it is envisaged that the boards providing the intersurfacial damping system may be spot adhered, mechanically fixed such as by nails, screws or staples or use self-locking tongue and groove systems built into the boards for example. The fixing of the boards may in fact be any system which allows for a substantial area of the adjacent layers to come into direct contact with each other. It is further envisaged that the multi-layered boards may be provided as a prefabricated product and not assembled in situ.

9 It is emphasised that the intersurfacial damping system may be used throughout a building construction whether this be for intertenancy floors/ceilings, walls or the like.

Also it is emphasised that the layering of the materials may be such that the same materials are not in contact. For example, the layers could be; floor covering/particle board/GFB/other material/GFB/floor covering. Also GFB could be the floor covering itself; in sufficient layers it becomes a structural component.

The gypsum fibre board which is a preferred material for use with intersurfacial damping (although it is stressed that other materials may be used) may suitably have a thickness of between 7 and 20 millimetres.

Preferably the gypsum fibre board is a high density fibre board including gypsum and paper fibre with a paper fibre included in the order of 10% to by weight. Preferably the gypsum fibre board may have a density of at least 20 1000kg/m 3 A board density of the order of 1300kg/m 3 may be utilised. It will be appreciated by those skilled in the building and engineering arts that any Salternative building materials could be substituted.

.In the following graphs, intersurfacial damping has for the sake of 25 simplicity been expressed in terms of, 0 degree, 1 degree, 2 degree, to state the number of effective intersurfacial damping interfaces.

In the testing of the building systems leading to the present invention a comparison of the present invention against the use of a resilient clip system, where a clip and batten system is used, was carried out. This is shown in Figure 7. It is seen that above 160Hz the intersurfacial damping provides improved sound control as shown by the bottom line in the graph.

In Figure 8 the bottom line of the graph shows that intersurfacial damping utilising an additional layer of board for the floor layer, provides greater benefit than providing an additional layer for the ceiling.

Turning to Figure 9 this graph shows that in tests of a timber framed intertenancy floor an additional layer, of gypsum fibre board for example, provided for the floor, either beneath or above the floor material itself such as particle board, timber strip flooring, compressed cement board or the like, provides more benefit than providing two ceiling layers.

Turning now to Figure 10 this graph illustrates the improvement obtained using intersurfacial damping of the floor using either a layer of particle board or using 7mm gypsum fibre board with the gypsum fibre board showing its better performance as an intersurfacial damping material compared to the particle board, i.e. interfacial damping effectiveness is dependant on material properties.

Referring now to Figure 11 the bottom line of the graph shows that two 7mm layers of gypsum fibre board provides significantly better sound control S°than a single thicker layer of the same material i.e. it is not the mass of the material which has provided the better sound control but the intersurfacial damping provided by utilising two layers of the material but with lesser mass.

20 In particular it is seen that the single layer system had a Lnw 61 dB whereas the multiple layer system had a Lnw 58 dB. Where "Lnw" is a single number rating from ISO 717-2, being the "weighted normalised impact sound pressure level" of a floor, the ASTM equivalent being IIC.

Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if incorporated as if individually set forth.

a a Although this invention has been described by way of example and with reference to possible embodiments thereof it is to be understood that modifications or improvements may be made thereto without departing from the scope or spirit of the invention as defined in the appended claims..

Claims (9)

1. A method of impact sound control for a building construction including the provision of intersurfacial damping (as herein defined) in a floor of the building construction by securing together of at least two sheets of material so that their respective adjacent surfaces are in contact over at least a substantial portion of their respective surface areas and wherein at least one sheet of material is of gypsum fibreboard, gypsum wood fibre or plasterboard.

2. A method as claimed in claim 1 wherein at least one of the sheets is a high density gypsum fibreboard.

3. A method as claimed in claim 2 including at least two of said sheets of said high density gypsum fibreboard.

4. A method as claimed in any one of the preceding claims wherein at least a second of said sheets is of plasterboard.

5. A method as claimed in any one of claims 1 to 4 wherein the floor is part of a 20 floor/ceiling system. Se

6. A method as claimed in claim 2 or claim 3 wherein the said high density fibreboard has a density of at least 1000kg/m 3 S• 25 7. A method of impact sound control utilising intersurfacial damping and substantially as herein described with reference to any one of the embodiments :of the invention as shown in Figure 1 or Figures 2A, B or C or Figure 4 or S: ~Figures 6A and B. 30 8. A building construction utilising an impact sound control method according to any one of the preceding claims.

9. A multi-layer assembly of sheets of material to provide impact sound control by intersurfacial damping (as herein defined) in a floor of a building construction in which the assembly includes at least two sheets of material secured together so that there is contact between at least a substantial portion of their respective

12- surface areas and wherein at least one of the sheets is of gypsum fibreboard, gypsum wood fibre or plasterboard. A multi-layer assembly to provide intersurfacial damping in a building construction as claimed in claim 9 in which at least one of the sheets is high density gypsum fibreboard. 11. A multi-layer assembly as claimed in Claim 10 including at least two sheets of said high density gypsum fibreboard and at least one sheet of a further board material, all layers being in contact between at least a substantial portion of their respective adjacent surface areas so as to provide said damping. 12. A multi-layer assembly as claimed in any one of claims 9 to 11 which is prefabricated for use in a building construction.

13. A multi-layer assembly for impact sound control substantially as herein described with reference to any one of the embodiments of the invention and with reference to Figure 1, or Figures 2A, B or C or Figure 4 or Figure 6A or B. ooo DATED this 2 9 th Day of September, 2005 Shelston IP Attorneys for: Fletcher Challenge Limited *o o go* oooo* o *go o*