NZ729239A - Breathable boundary wall system - Google Patents

Abstract

breathable boundary wall system for closely spaced “Zero lot” building constructions comprising: at least one load-bearing substrate for supporting a first wall section; the first wall section comprising: a frame section 130, the frame section comprising at least first and second opposing major faces 131 and 132. A breathable cladding material 140 is fixed to the first major face of the first frame section, for forming an external cladding on the first wall section; and a second wall section erected on a load bearing substrate and spaced apart from the first wall section to define a gap 180 therebetween; wherein the first wall section and the gap defined between the first wall section and the second wall section together define the breathable boundary wall system. In preferred forms the wall system includes a capping across the gap. ces 131 and 132. A breathable cladding material 140 is fixed to the first major face of the first frame section, for forming an external cladding on the first wall section; and a second wall section erected on a load bearing substrate and spaced apart from the first wall section to define a gap 180 therebetween; wherein the first wall section and the gap defined between the first wall section and the second wall section together define the breathable boundary wall system. In preferred forms the wall system includes a capping across the gap.

Description

BREATHABLE BOUNDARY WALL SYSTEM FIELD OF THE INVENTION The present invention relates to building construction and in particular to boundary wall systems in building construction.

The invention has been developed primarily for use as a breathable boundary wall system for use in medium density residential construction and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

BACKGROUND OF THE INVENTION Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.

Medium density residential construction methods are known, requiring a smaller sized residential construction block of land for each dwelling than in traditional house construction. This results in smaller amounts of land that are not occupied by dwelling space, and therefore in smaller parcels of land to be maintained by occupants. To achieve this, medium density development dwellings may be constructed as “row” housing or attached dwellings. In row housing, each tenancy is separated from its adjacent tenancy by a single “common” wall, resulting in an attendant reduction in acoustic isolation of each tenancy.

In such medium density construction, the whole “terrace” or “row” of buildings is usually constructed at once and the whole row has to be completed before a builder can begin selling individual dwellings.

Multi-residential medium density developments, where individual dwellings are constructed on a single block of land, are known. However, as the size of available land blocks decreases and the pressure for an increased number of dwellings per block of land increases, with existing cladding construction techniques there is still a minimum gap required between freestanding dwellings to allow for construction activity and post- construction building maintenance such as painting of exterior walls for weather protection.

This limits the number of dwellings per lot and also adds costs to a dwelling construction by requiring additional paving or landscaping and the like between individual dwellings.

The most recent evolution of this trend of multi-residential medium density developments has been the “Zero Lot” style of construction where buildings extend to, or very near, their boundary line. Typically, these have been built using masonry type construction due to the access restrictions that prevent building in the normal “light construction” style of erecting a structural frame and then fixing cladding to it to form an exterior wall surface.

It is also possible to use a panelised system which is constructed at an alternate location and then moved into place for installation on the “Zero Lot” multi-residential medium density development. Typically, the panelised system uses exterior cladding fixed to a structural frame section. In practice, difficulties arise, as the panelised system is often constructed in an area adjacent to the “Zero Lot” multi-residential medium density development. Usually, the panelised system is created in a horizontal orientation relative to ground level and then tilted into a vertical orientation and moved into the correct position for installation on the “Zero Lot” development. The exterior cladding is also usually painted and allowed to dry prior to finalizing installation, meaning the builder has a cost burden of additional trades skills and time delay prior to completion of installation.

In buildings having an internal and external cladding fixed to a structural support frame, and both claddings are covered by a surface barrier layer such as a paint, there is an opportunity for any water that ingresses into the cavity between the cladding materials to be trapped and unable to dry out in a timely manner if insufficient cavity venting has been provided or vents have been compromised by accumulation of debris. In a Zero lot construction style, in particular, where post-construction access to the external wall cladding is limited or impractical, remedying any such issues is problematic.

It is desirable to provide a breathable boundary wall system for use in medium density construction.

OBJECT OF THE INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

It is an object of the invention in its preferred form to provide a breathable boundary wall system for use in medium density construction to reduce time and cost of construction, to reduce or eliminate post construction maintenance, and to enable drying of moisture from wall cavities.

SUMMARY OF THE INVENTION According to the invention, there is provided a breathable boundary wall system comprising: at least one load-bearing substrate for supporting a first wall section; the first wall section comprising: a frame section, the frame section comprising at least first and second opposing major faces; a breathable cladding material fixed to the first major face of the first frame section, for forming an external cladding on the first wall section; and a second wall section erected on a load bearing substrate and spaced apart from the first wall section to define a gap therebetween; wherein the first wall section and the gap defined between the first wall section and the second wall section together define the breathable boundary wall system.

Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

The term wall section is used herein to refer to the portion of a wall that forms part of a boundary wall system. For example in a row of longitudinally aligned buildings, the wall section may comprise the whole boundary wall. By contrast, if the adjacent buildings are offset transverse to the direction of the row, the wall section may comprise only that portion of the wall that overlaps with the adjacent wall to form part of the boundary wall system.

In one embodiment, the first and second wall sections each comprise; a frame section, the frame section comprising at least first and second opposing major faces; a first breathable cladding material fixed to the first major face of the frame section for forming an external wall cladding on a wall section; and wherein the first and second wall sections are supported on the load-bearing substrate, the first wall section being spaced apart from the second wall section to define a gap therebetween, the first wall section and the gap defined between the first wall section and the second wall section together defining a breathable boundary wall system.

Preferably, a capping or flashing is provided across the top of the gap between the first wall section and the second wall section.

In one embodiment, the first breathable cladding material is impermeable to water when in a liquid phase but permeable to water vapour wherein water is in a gaseous phase.

In one embodiment, the first breathable cladding material is a substantially rigid material.

In one embodiment, the first breathable cladding material is fibre cement.

In one embodiment, the first breathable cladding material is panelised wherein the first breathable cladding material comprises a panel having at least two major opposing faces, wherein the at least two major opposing faces are spaced apart from each other; and a side edge intermediate to and contiguous to the spaced apart at least two major opposing faces. In one embodiment, at least a portion of the side edge of the panelised first breathable cladding material is profiled. Conveniently in a further embodiment, at least two portions of the side edge of the panelised first breathable cladding material are profiled. In a further embodiment, the at least two profiled portions of the side edge are opposing profiled portions. In use, the opposing profiled portions provide complementary interlocking panel engaging means for adjacently seated panels.

In one embodiment, the first and second wall sections further comprise an insulating material. Conveniently, the insulating material is positioned on or within each frame section intermediate the first breathable cladding material and the second cladding material.

In one embodiment, the first wall section and second wall section may be supported by a single load bearing substrate.

In other embodiments, the first wall section and second wall section are each supported by a discrete load bearing substrate.

In one embodiment, the second wall section is a pre-existing boundary wall section.

In one embodiment, the width of the gap defined between the first wall section and the second wall section is less than 0.5 metres.

In one embodiment, the frame section comprises a timber frame.

In one embodiment, the frame section comprises a metal frame.

In one embodiment, a flexible weather barrier is disposed between the first breathable cladding material and the first frame section.

In one embodiment, the first wall section further comprises a second cladding material fixed to the second major face of the first frame section.

In one embodiment, there is provided a method of constructing a breathable boundary wall system comprising the steps of: a. building a wall section frame; b. cladding the first major face of the frame section with an uncoated weather resistant and breathable first cladding material; c. erecting the first frame section spaced apart from a pre-existing wall section to define a gap therebetween, wherein the first wall section and the gap between the first wall section and the pre-existing wall section together form the breathable boundary wall system.

In one embodiment, there is provided a method of constructing a breathable boundary wall system comprising the steps of: a. building a first wall section frame; b. cladding the first major face of the first frame section with a weather resistant and breathable first cladding material; c. erecting the first frame section d. building a second wall section frame; e. cladding the first major face of the second frame section with a weather resistant and breathable first cladding material; f. erecting the second wall section spaced apart from the first wall section to define a gap therebetween, wherein the first wall section and the gap between the first wall section and the second wall section together form the breathable boundary wall system.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cross-sectional side view of a breathable boundary wall system according to one embodiment of the invention, where the second wall section is a pre- existing wall section; Figure 2 is a cross-sectional top view of a breathable boundary wall system according to one embodiment of the invention, where the second wall section is constructed in the same manner as the first wall section; Figure 3 is a schematic top view of a prior art example of medium density construction showing “common wall” construction between tenancies; Figure 4 is a schematic top view of medium density construction using a breathable boundary wall system according to the present invention; Figure 5 is a cross-sectional view of a further embodiment of the invention wherein the first and second wall sections are constructed in similar manners showing a first equal height roofing and capping example; and Figure 6 is a cross-sectional view of a further embodiment of the invention wherein the first and second wall sections are constructed in similar manners showing a second stepped roofing and capping example.

PREFERRED EMBODIMENT OF THE INVENTION The terms dwelling and tenancy, either in their singular or plural forms, are used interchangeably throughout the specification and refer to an occupancy space in a building.

Dwelling is more commonly used for building spaces with a residential purpose, whereas tenancy is a broader term and can refer to occupation of a building space for either residential and non-residential purposes. The invention is described in terms of residential dwellings but is equally suitable for non-residential construction.

Throughout this specification, construction details which are not relevant to the present invention, such as those regarding decorative trims and the like, have been omitted in the interests of clarity. Persons skilled in the art will understand that, although they are not detailed here, they would form part of normal building practice.

Referring to the drawings, Figure 1 shows a breathable boundary wall system 100 which comprises at least one substrate 110, each substrate supporting at least one wall section; a first wall section 120 comprising: a first frame section 130 erected on a substrate; a breathable first cladding material 140 fixed to a first major face 131 of first frame section 130, for forming an external cladding on the wall section; and a second cladding material 150 fixed to a second major face 132 of first frame section 130, for providing an interior wall cladding in a wall section, and second wall section 170, erected on substrate 110 and spaced apart from first wall section 120 to define a gap 180 therebetween, wherein first wall section 120, second wall section 170, and gap 180 defined therebetween together define a breathable boundary wall system.

Typically substrate 110 is a raft or mat type foundation in the form of a concrete slab or the like. It would be constructed to support the entire footprint of a construction project, such as a single dwelling or a number of adjacent dwellings. Alternate substrates, such as piers, strip footings, piles, and the like, may be used according to local building practice and regulations and may vary between adjacent dwellings.

In this building system, the constructed breathable boundary wall is too closely positioned against another building to allow for the traditional construction practice of constructing the whole building frame and then installing the exterior cladding. In one embodiment of this invention, construction of first wall section 120 is begun by building a first frame section 130 as a standalone unit, generally laying flat on a support surface, such as the ground, near its intended installation position. Frame section 130 may be constructed of timber or metal according to applicable local building code or regulations.

Each frame section 130 for each wall that will be immediately adjacent a lot or sub- lot boundary is constructed separately.

Breathable first cladding material 140 fixed to first major face 131 of the frame section 130, for forming an external cladding on first wall section 120. The breathable first cladding material 140 is a fibre cement building product in the form of a substantially rigid panel or plank product. In all embodiments of the present invention, the fibre cement product is formulated or treated to be permeable to water vapour but not to liquid water, thereby allowing for drying of any water that ingresses the wall cavity. It is important to this invention that the fibre cement product has no full barrier coating at the boundary region, such as paint, applied prior to or after installation, so that its water vapour permeability is not compromised in service. If adjacent dwellings are offset, such that portions of the walls are exposed, then painting of the exposed regions is acceptable and recommended.

Where breathable first cladding material 140 is a fibre cement material, it is made permeable to water vapour and impermeable to liquid water either by inclusion of an additive such as a polymeric material, for example a long chain copolymer, into the formulation, or by post-autoclaving treatment with a breathable hydrophobic material such as a polymeric material such as a copolymer, or silane or siloxane or silicone based compounds, without forming a barrier layer on the surface of the fibre cement. The resultant fibre cement product is an uncoated, weather resistant, breathable fibre cement product. Suitable copolymers for use in the formation of a breathable fibre cement material include terpolymers derived from ethylene, vinyl chloride and/or vinyl laurate. The terpolymers optionally also include silane based functional groups. Either approach, unlike conventional paints, does not require the formation of a barrier type coating as an applied surface layer. One advantage of breathable first cladding material 140 is that no further treatment is required during construction, and breathable first cladding material 140 can be installed by fixing to first frame section 130 in the “as received” condition. Not requiring the on-site application of a barrier coating provides a benefit to builders in reducing the number of trades required during construction, reducing the time of construction, and therefore also reducing the cost of construction. All of which also are of benefit to a consumer, in this case, a tenant or dwelling occupant, by reducing the time they must wait before being able to occupy their dwelling or tenancy.

Optionally, a flexible weather barrier 142 such as a building wrap or building paper can be used between the frame section 130 and breathable first cladding material 140, to provide additional water management, and/or thermal insulation performance to the wall construction.

Once breathable first cladding material 140 has been installed onto the frame section 130, it can be lifted into position and secured to load-bearing substrate 110 with any suitable conventional fixing means, for example mechanical fixing means such as screws, nails, bolts, and the like. First wall section 120 can be installed between 10mm and 500mm from second wall section 170, and more usually first wall section 120 and second wall section 170 are spaced apart by between 12.5mm and 100mm to define gap 180. First wall section 120 and second wall section 170 may typically be spaced apart by between approximately 12.5 and 50mm to define gap 180 and provide the most practical minimum spacing between adjacent wall sections . Gap 180 is substantially protected from direct exposure to environmental agents such as driving rain, windblown grit, or direct sunlight and UV radiation by virtue of its narrow width and use of suitable capping elements, overhangs or flashings and the like as described hereafter with reference to Figures 5 and 6, but with sufficient clearance to enable any moisture vapour transported outwards through breathable first cladding material 140 and into gap 180 to evaporate without condensing on the surface of either second wall section 170 or first wall section 120.

In buildings having an internal and external cladding fixed to a structural support frame, and both claddings are covered by a surface barrier layer such as a paint, there is an opportunity for any water that ingresses into the cavity between the cladding materials to be trapped and unable to dry out in a timely manner if insufficient cavity venting has been provided or vents have been compromised by accumulation of debris. It is an advantage to dwelling occupants or tenants to have a breathable cladding material included in the breathable boundary wall system to allow transport of any accumulated water, as vapour, through the exterior cladding material and into the gap between the first and second wall sections, particularly as post construction access to the exterior cladding on the boundary wall in zero lot construction is limited at best. The gap is sufficiently large that any water vapour transported through a breathable cladding material can be dispersed into the relatively larger air volume of the gap. The gap is also not sealed to an airtight finish, so any water vapour transported into the gap can disperse over time.

Other wall sections of the dwelling that are not immediately adjacent and facing the lot boundary, or which do not have obscured access can then be installed in the traditional way, to complete the exterior building envelope.

Once the exterior wall frame sections are installed, optional insulating material 160 can be used to at least partially fill interior of first frame section 130 to increase the thermal and/or acoustic performance of the wall. Any commercially available insulation that meets local building codes and regulations is suitable. Examples of suitable insulating materials are polymeric or inorganic wools such as rockwool or polyester wool, or polymeric foams such as polyurethane or polyisocyanurate foams.

Second cladding material 150 in the form of an interior cladding material such as fibre cement, gypsum board, timber paneling and the like can then be fixed to second major face 132 of first frame section 130 using fixings 148, to complete the wall section 120.

Completion and occupation of each dwelling or tenancy can occur, irrespective of the stage of construction of any other dwellings or tenancies in the development, providing an advantage to builders and developers.

In one embodiment of the invention, once construction of two adjacent dwellings is complete, a capping material of any suitable construction material such as timber, metal or fibre cement trim, can be used to provide a cover of the gap and for preventing access of pests or accumulation of debris into the gap such as is shown in Figures 5 and 6. If breathable boundary wall system 100 is installed adjacent an existing building then at least part of an existing exterior wall of that building will form second wall section 170. In Figure 1, the existing wall that forms second wall section 170 is a brick wall set on its own supporting substrate 111, independent of substrate 110 supporting wall section 120.

Similarly, a capping material can be used in such an example to provide a cover of the gap between the constructed dwelling and the existing building for preventing access of pests or accumulation of debris into the gap.

The wall section 120 is positioned on substrate 110 and secured by fixings 148.

The positioning of first wall section 120 relative to second wall section 170 defines gap 180.

Second wall section 170, first wall section 120, and gap 180 therebetween, together defining breathable boundary wall system 100.

In one embodiment of the invention, as best seen in Figure 2, breathable first cladding material 140 is a panelised breathable fibre cement cladding material, each panel having at least one pair of opposing side edges comprising first complementary interlocking edge profile 145, and second complementary interlocking edge profile 146 forming respectively the underlap and overlap edge profiles of a complementary interlocking panel means in the form of an overlapping shiplap joint when two panels are installed adjacent each other in a wall section. In some embodiments (not shown)the complementary interlocking panel means, such as a shiplap style joint, may be fixed to first frame section 130 by secret nailing, that is, fixing only through the underlap portion of the shiplap joint into first frame section 130. In such an installation style, the overlap portion of the shiplap joint would further include a separate locking formation that interlocks with the underlap portion and retains the overlap portion in position. Alternatively, the joint strength of an overlapping shiplap joint can be improved by face nailing through both panels and into the first frame section 130, at a recommended distance from each respective panel edge, for additional bracing strength. While the illustrated embodiment show panels joining along a horizontal edge, in other embodiments the joins can be vertical or any other suitable inclination.

In other embodiments, some form of metal or polymeric panel jointer system can be used to connect and finish the edges of the panels which may, or may not, include profiled edges.

In Figure 2, both first wall section 120 and second wall section 170 are new construction, part of a multi-residential dwelling development. A benefit of this construction system is that once the dwelling containing second wall section 170 has been completed, it may be sold and occupied while first wall section 120 is still under construction, with no inconvenience to the occupants of the completed dwelling. The advantage to a builder is that they do not need to wait until construction of an entire multi-residential medium density development is completed before selling individual tenancies. A benefit for consumers is that they may purchase and occupy a dwelling without similarly needing to wait until construction of the entire development is complete.

At least both dwellings shown in Figure 2 are supported by a single substrate 110 (not shown) in the form of a concrete slab type raft foundation. Where several detached dwellings may be constructed sequentially using boundary or “zero lot” construction methods, separate concrete slabs may be poured with each slab supporting an individual dwelling. Alternatively, two or more dwellings may be constructed on a single substrate 110 such as a concrete slab, with slab separations with flexible bond breaker where required, or sets of piers. Where new construction is located on a small urban building lot, it is likely that at least one dwelling may be constructed close by a pre-existing building.

An example of a typical “row house” according to prior art construction methods is shown in Figure 3, in which row house 300 has multiple dwelling spaces 320 formed by a combination of exterior walls 310 forming the perimeter of the building and “common walls” 330 between individual tenancies. In this type of construction, all walls, exterior and common walls, are constructed at the same time. The row house is, in effect, built as a single construction and no tenants may occupy their dwelling or tenancy space until the whole building is complete.

In this type of construction, finishing of the building interiors such as by installation of interior wall claddings, cabinets, electrical connections, plumbing and the like are not begun until the wall construction is complete and the roof has been installed. This construction method effectively delays the occupancy of all tenancies until all are complete.

In contrast, as shown in Figure 4 in one embodiment of the invention, a row of medium density zero lot construction style dwellings 400 constructed using the breathable boundary wall system are shown, each dwelling space 420 being completely separate from every other dwelling space. Dwelling 1, for example, may be completed and occupied prior to completion, or even commencement, of Dwelling 2 and so on. It also enables construction with a gap of less than 0.1m, which significantly increases land yield.

Referring next to Figures 5 and 6 there are shown examples of different roofing configurations and capping arrangements suitable for use with those configurations. To this end Figure 5 shows a trussed roof with roof trusses 200 and tiles 210. In this arrangement the first and second walls are of equal height and the gap 180 is covered by a simple horizontal capping arrangement 220.

By contrast, Figure 6 shows a flat stepped roof configuration, where at the boundary the first and second walls are of a slightly different height. In this case the gap 180 is covered by a capping and flashing arrangement 230 that extends over the gap and over the exposed portion 240 of the breathable cladding 140 of the heighest wall section.

A method of constructing a breathable boundary wall system comprising the steps of: building first wall section 120 comprising constructing a first frame section 130 cladding first major face 131 of the first frame section 130 with breathable first cladding material 140; and erecting first frame section 130 on substrate 110, spaced apart from second wall section 170 to define gap 180 therebetween.

Breathable first cladding material 140 is preferably a substantially rigid, breathable panel or plank product, such as a breathable fibre cement panel or plank product, formulated or surface treated during manufacture to be substantially impermeable to liquid water but substantially permeable to water vapour.

Optionally, flexible weather barrier 142 can be installed prior to cladding first major face 131 of first frame section 130.

Optional insulating material 160 can be used to at least partially fill spaces within first frame section first frame section 130.

It will be appreciated that the illustrated breathable boundary wall system for use in medium density construction, reduces time and cost of construction, reduces or eliminates post construction maintenance and enables drying of moisture from wall cavities.

Although the invention has been described with reference to specific examples, it will be understood by those skilled in the art that the invention may be embodied in many other forms.

Claims (26)

1. A breathable boundary wall system comprising: at least one load-bearing substrate for supporting a first wall section; the first wall section comprising: a frame section, the frame section comprising at least first and second opposing major faces; a first breathable cladding material fixed to a first major face of the frame section, for forming an external cladding on a wall section; and a second wall section spaced apart from the first wall section to define a gap therebetween, wherein the first wall section and the gap defined between the first wall section and the second wall section together define a breathable boundary wall system.

2. A breathable boundary wall system according to claim 1 wherein the first and second wall sections each comprise; a frame section, the frame section comprising at least first and second opposing major faces; a first breathable cladding material fixed to the first major face of the frame section for forming an external wall cladding on a wall section; and wherein the first and second wall sections are each supported on a load-bearing substrate, the first wall section being spaced apart from the second wall section to define a gap therebetween, and wherein the first wall section and the gap defined between the first wall section and the second wall section together define a breathable boundary wall system.

3. A breathable boundary wall system according to claim 1 or claim 2 further including a capping that extends across the gap between the first wall section and the second wall section.

4. A breathable boundary wall system according to any one of the preceding claims, wherein the first breathable cladding material is impermeable to liquid water but permeable to water vapour.

5. A breathable boundary wall system according to any one of the preceding claims, wherein the breathable first cladding material is fibre cement.

6. A breathable boundary wall system according to claim 5 wherein the fibre cement material is made permeable to water vapour and impermeable to liquid water by inclusion of a suitable additive into the formulation.

7. A breathable boundary wall system according to claim 6 wherein the additive includes or consists of a copolymer.

8. A breathable boundary wall system according to claim 5 wherein the fibre cement material is made permeable to water vapour and impermeable to liquid water by post- autoclaving treatment with a breathable hydrophobic material.

9. A breathable boundary wall system according to claim 8 wherein the breathable hydrophobic material includes or consists of one or more of: a copolymer, or silane or siloxane or silicone based compounds.

10. A breathable boundary wall system according to any one of the preceding claims, wherein the breathable first cladding material is at least one substantially rigid panel.

11. A breathable boundary wall system according to claim 10, wherein each panel comprises at least two profiled opposing side edges.

12. A breathable boundary wall system according to claim 11 wherein the profiled opposing edges facilitate a ship lap joint connection of adjacent panels.

13. A breathable boundary wall system according to claim 10 wherein the panels are configured to be joined by a jointer system.

14. A breathable boundary wall system according any one of the preceding claims, wherein the first wall section further comprises an insulating material at least partially filling each frame section.

15. A breathable boundary wall system according to any one of the preceding claims, further comprising a second cladding material fixed to the second major face of each first frame section.

16. A breathable boundary wall system according to any one of the preceding claims, wherein the first wall section and second wall section may be supported by a single load bearing substrate.

17. A breathable boundary wall system according to any one of claims 1 to 15, wherein the first wall section and second wall section are each supported by a discrete load bearing substrate.

18. A breathable boundary wall section according to any one of the preceding claims wherein the second wall section is a pre-existing boundary wall section.

19. A breathable boundary wall system according to any one of the preceding claims, wherein the width of the gap defined between the first wall section and the second wall section is less than 0.5 metres.

20. A breathable boundary wall system according to any one of the preceding claims, wherein the frame section comprises a timber frame.

21. A breathable boundary wall system according to any one of the preceding claims, wherein the frame section comprises a metal frame.

22. A breathable boundary wall system according to any one of the preceding claims, wherein a flexible weather barrier is disposed between the first breathable cladding material and the frame section.

23. A breathable boundary wall system according to claim 22, wherein the flexible weather barrier is a building wrap or building paper.

24. A method of constructing a breathable boundary wall system comprising the steps of: a. building a wall section frame; b. cladding the first major face of the frame section with a weather resistant and breathable first cladding material; c. erecting the clad first frame section spaced apart from a pre-existing wall section to define a gap therebetween, wherein the first wall section and the gap between the first wall section and the pre-existing wall section together form the breathable boundary wall system.

25. A method of constructing a breathable boundary wall system comprising the steps of: a. building a first wall section frame; b. cladding the first major face of the first frame section with a weather resistant and breathable first cladding material; c. erecting the clad first frame section d. building a second wall section frame; e. cladding the first major face of the second frame section with a weather resistant and breathable first cladding material; f. erecting the second wall section spaced apart from the first wall section to define a gap therebetween, wherein the first wall section and the gap between the first wall section and the second wall section together form the breathable boundary wall system.

26. A breathable wall system substantially as herein described with reference to the accompanying drawings.