CLADDING SYSTEM FOR BUILDINGS
A cladding system, intended to exclude water from within a building having a cavity wall structure, includes passive means (a) for minimising any flow of water from the exterior that may reach the interior, and (b) open guides or enclosed channels for diverting such water so that it flows by gravity down the cavity to be drained outwardly. One implementation provides impervious battens modified to have water-diverting sides, and another provides solid slabs including channels connected by drainage cuts along their length to a surface to be drained.
This invention relates to a cladding system, related components, and a cladding method for use on buildings and in respect to exclusion of water from the building. More particularly the invention provides physical items capable of serving as moisture insulation means.
ABBREVIATIONSBatten=a nailable or fastenable elongated strip of material, its thickness sets the cavity depth. May be vertical or horizontal.
DPC=Damp Proof Course
EIFS=Exterior Insulation and Finishing System
EPS=expanded polystyrene
Stud=a vertical timber member of a wooden frame, such as in a house wall.
Nog (also called dwang)=a horizontal timber member of a wooden frame, (fixed in between studs) such as in a house wall.
Plate=a horizontal timber member of a wooden frame, above or below the studs, such as in a house wall.
BACKGROUNDBuildings to be inhabited are meant to keep water (such as rain) out and in any case should remain substantially dry, in order to prevent rotting and to maintain a comfortable internal environment. Many cladding systems for buildings use external sheets of EPS, EIFS, fibrous cement board, plywood, metal, wood or any other material, and generally rely on an exterior coating such as a paint finish over the outer cladding sheets to prevent the penetration of moisture from the outside. This barrier can be easily breached, allowing moisture (that is, water) to enter or pass through the cladding material. Thereafter the water can accumulate behind the cladding layer, in part owing to the inability of the water to exit this layer. Water may penetrate by mass flow, by capillary action, or may be blown in by pressure from wind.
Water management difficulties can sometimes arise, from water evolved within a building such as by human activities and by gas heating. For instance water vapour migrating from the inside of a building may pass through a breather type building paper/vapour barrier, which permits the vapour to condense and become trapped between the outer cladding layer and an inner supporting structure. Any accumulation of moisture will tend to migrate to adjacent drier materials or colder surfaces due to water equalisation. In time the accumulated water passes through building paper/vapour barriers in part because such barriers generally are attached to the structure beyond by fixing systems that penetrate the barrier.
In particular where the supporting structure is timber or a stud and nog wall, such trapped dampness or water can lead to rotting of the supporting structure, which is dearly disadvantageous. Equally, for masonry structures, the collection and migration of water may cause undesirable internal dampness, and the physical and visual degradation of adjacent materials, which is equally disadvantageous.
In recent times, use of a cavity within an exterior wall, enclosing an inner structure, has become accepted building practice. Hence the water-resistant cladding becomes separate from the internal walls. One advantage of having a cavity in a wall, between the external cladding member (which acts as a weather barrier and can become very wet) and a building's support structure, which is preferably kept relatively dry, is that a cavity helps prevent water from reaching the support structure inside. Industry authorities recommend that the cavity (separation) should be a minimum of 20 mm wide.
In order to cope with a problem of damp habitations, the construction industry has recently suggested it should be (a) mandatory to include a cavity that is a minimum of 20 mm wide behind any monolithic plaster cladding, and (b) desirable to supply a cavity behind other cladding materials. Such a cavity could be made by using vertical battens outside a vapour barrier and inside a cladding material, so as to allow moisture to run downwards and drain to the outside of a building. But, horizontal battens are generally also required to support cladding sheet edges and to prevent the middle of some types of cladding sheet from flexing or “scalloping” when being subjected to strong winds or other external forces. Unmodified horizontal battens tend to obstruct moisture from exiting the building quickly. If the battens are “water absorbent”, they can hold and absorb the escaping moisture and transfer it to the vulnerable building structure through moisture equalisation, also, perhaps, rotting as a result of fungal or insect attack. This is dearly undesirable.
Treated timber battens may be used as spacers (i,e, to create a cavity) over the wall support structure; also with a DPC between the batten and the rear face of the cladding sheet to prevent moisture migrating into the timber batten. Another problem is that the fasteners used to fix the DPC to the batten, as well as fasteners used for the cladding sheets will puncture and therefore compromise the DPC's integrity, potentially allowing moisture to soak into the batten and into the structure beyond.
EPS battens are known, but have similar moisture absorption issues to the timber battens, as well as a whole range of other limitations. Most battens are not strong and may need to be installed vertically over the studs of the underlying support structure which can be impractical when the cladding sheet borders, as supplied, do not correspond to the location of the studs (where the battens are attached) resulting in waste, and increased costs in time and labour to mark and cut the sheets so that they match the lines of the studs. Also, in a typical 2.4 metre high timber stud frame, two horizontal rows of nogs would normally be provided, equally spaced between the top and bottom plates. Hence any proposed vertical battening system would need to span the 800 mm (approx) between nogs and top and bottom plates. Treated timber battens, being 20 mm to 30 mm deep (corresponding to the depth of the cavity required), are usually too flexible for cladding support if used to span gaps between the nogs. In addition, driving, screwing or hammering a fastener into a timber batten while constructing a wall is likely to split that batten.
A disadvantage of members that bridge the gap between the cladding and the interior wall is that the members may serve as bridges for water that contacts, drains down, and permeates the inner structure. For example, when the wind drives rainwater into window or door openings, it can be forced across and up the sill or threshold of the opening, toward the window/door joinery unit itself. It is common for cracks or gaps to exist where a window/door joinery unit abuts the sill of a cladding member below, because they have different expansion characteristics. Such a crack permits the entry and accumulation of water behind the joinery unit.
PRIOR ARTRelevant prior art is described along with corresponding examples in the Preferred Embodiment.
OBJECTIt is an object of the present invention to provide water expulsion and water expulsion means for use as part of a cladding system for a building, or at least to provide the public with a useful choice.
STATEMENT OF INVENTIONIn a first broad aspect the invention provides a cladding system for use underneath an external surface of an exterior wall of a building, wherein the cladding system provides a combination of physical, passive means within a cavity of the wall, the means capable of at least partially obstructing the movement of water across the cavity towards an internal, water-susceptible structure of the building, and means capable of at least partially causing the water to flow out of and be expelled from the cavity, thereby protecting the internal, water-susceptible structure from water.
In a first related aspect, the cladding system is comprised of a plurality of elongated, substantially impermeable members herein called battens, each batten having a first surface for receiving an exterior cladding panel and a second, opposed surface for mounting upon the underlying inner structure, the surfaces of the batten being separated on each side by a side surface bearing water path diverting means, so that when in use in a substantially vertical orientation, water drops, films or droplets attempting to pass towards the internal structure are intercepted and encouraged to flow downwards and out from a base of the wall.
Preferably the water diverting means as applied to a vertically oriented batten comprises at least one longitudinal fin and so that a pocket between the fin and the cladding panel comprises an open channel; thereby creating a preferential path for water flow.
Preferably the water diverting means comprises at least one longitudinal everted ridge, or optionally, the water diverting means comprises at least one longitudinal inverted valley.
In another version, a preferred water path-diverting means comprises at least one series of elongated, slanted surface modifications, each surface modification being slanted towards the cladding side at a lower end, so that, when in use, water is guided by the slanted orientation of the surface modification downwards and towards the cladding side of the batten.
Alternatively the or each surface modification comprises an elongated raised dome.
A further alternative surface modification comprises an elongated depression.
A yet further surface modification comprises an elongated aperture.
Preferably the water diverting means as applied to a horizontal batten comprises providing at least one longitudinally sloped side on the batten, so that, when in use, the slope is oriented downwardly and outwardly away from the internal structure so that water is diverted in a direction away from the internal structure and towards.
In a second related aspect, the cladding system provides a plurality of masses as an array of substantially rigid slabs; each slab having a first surface for receiving a cladding sheet and a second, opposed surface for mounting upon an underlying structure; each slab containing a plurality of continuous parallel internal channels, which channels, when oriented in an at least partially vertical direction, are capable of conveying the water towards a lower end of the channel.
In one option, each channel is parallel to and is at least intermittently connected through a slit to the first surface.
Preferably, when in use, each substantially rigid slab employs capillary action through the slit to draw water from the first surface towards the internal channel
Optionally each substantially rigid slab includes several rows of internal channels each channel being connected at least intermittently through a water-receiving slit to the first surface.
In a second broad aspect, the invention provides a method of installing a cladding system as previously described in this section, wherein the method includes the steps of affixing a plurality of substantially rigid slabs on to an underlying structure so that the internal channels in each slab are oriented vertically, and in line with channels on other slabs above or below them, then of affixing at least one cladding panel over the plurality of substantially rigid slabs, and of arranging draining means to carry water from the lowest point of the internal channels towards an exterior of the building.
In another related aspect, the method includes the further steps of providing articles within apertures included within a wall with drainage means, by use of substantially rigid slabs with draining slits adjacent the aperture as well as adjacent the cladding.
Preferred EmbodimentsThe description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention.
Throughout this specification, unless the text requires otherwise, the word “comprise” and variations such as “comprising” or “comprises” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. Orientation terms such as “vertical” or “horizontal” should be construed broadly.
This invention applies to a variety of methods intended to resist the horizontal movement of water that has appeared within a wall, across the wall and into an internal structure, and to encourage the vertical movement of the water downwardly and directing it away from the structure, so that it can be passively expelled from the building before reaching the structure of the building and causing the well-known problems associated with damp or leaky buildings.
Each method of this cladding system may be used alone or in combination with the others.
This invention relates to providing cavities within exterior walls for buildings, of the type where an outer, weatherproof panel (at least as defined in terms of water ingress) is fixed over an inner structure that may be only partially moisture-proofed (such as by a layer of tarred paper or a reflective or permeable (breathable) foil sheet, and is itself susceptible to degradation in the presence of water and in the “leaky building problem”. There is an empty cavity between the inner and outer walls. The usual construction sequence creates the inner structure or panel layer first. By “degradation” the inventor includes attack by microbes, especially fungi, and physical change and deterioration of materials, adhesives and components of composite materials over the intended lifetime of a building. Further, the existence of dampness within an inhabited space is undesirable, unhealthy and unpleasant.
A preferred method to fix the cladding panel over the internal structure is by means of nailable battens first fixed onto the inner structure, preferably over joints, and then the outer panel is fixed over the battens. Typically the battens run in vertical and also horizontal directions. This is a widely practiced procedure, but improvements have recently been made: see for example the prior art publication WO2007/087681, which provides improved battens with a “finish ready panel supporting surface”. It is silent about water ingress or water management.
This invention serves to discourage water transfer from the cladding panels (including water arising by condensation) into an internal structure, and serves to encourage the formation of a gravity-driven flow of water down through the cavity to be expelled out of the bottom of the cladding system. It does so by passive means, relying on shapes, gravity, and the properties of water.
Refer to
See also
Where a non-sheet cladding element 40 is used (e.g. weatherboards etc), the battens 1 can be installed at vertical spacings capable when in use of satisfying all relevant design loads and requirements for the specific application. If the support structure is masonry, concrete, brick masonry or any other substantially planar structure 30, the battens 1 can be installed over that structure as “strapping” with appropriate fixing elements 19 at spacings that suit the requirements of the cladding material 40.
Prior art: One alternative to a nailable batten is provided by the dual effect of sloped fingers on an impervious though perforated panel: U.S. Pat. No. 6,298,620. Another alternative is provided by the rolled corrugated material of CA2469365; also perforated in places. Both examples define a cavity wall space but neither is believed to be as useful in the structural sense as are battens.
For the wall system as described to this point, a problem relates to the physical connection made by the battens 1 and 10, and the Z-flashing between the cladding panel and any inner structure 30. Even impervious battens may carry water (perhaps arising from condensation from saturated air within the cavity space, against a cold cladding panel, or from a leak to the outside through or bypassing the cladding panel) over their sides across the cavity 7 and to make contact with the inner support structure 30. Furthermore, wind may assist migration of this water across the cavity. As a result, even despite the presence of the barrier or DPC 36, degradation may be initiated. Many means to prevent such transfer are known for ties between bricks, such as GB151755 Ashgrove, or U.S. Pat. No. 4,177,617, both of which provide a point or line that serves as a focus for the formation of a drip.
Therefore the cladding system of the invention, in a first version, makes improvements to the batten sides in order to obstruct and divert frank water as drips or funnels downwards and to escape from the wall cavity. Regarding prior art, the inventor is aware of U.S. Pat. No. 5,634,300 which is called a “post” for use in supporting the edges of cladding panels. This elongated member has a number of side ridges, but they are specifically formed for use as T-bolt attachment means for post-to-post attachments. The patent document does not mention water exclusion. A number of non-limiting examples of improved battens will now be described.
EXAMPLE 1A fastenable batten in elongated shape is provided. The wide choice of preferred materials includes those that are preferably nailable, are rigid and robust, and are fit for purpose. Hence materials range from strips of wood, preferably treated so as to be fungi-resistant and impervious to moisture, through plastics, composite materials such as fibro-cement (water-impervious), and metals; for instance rolled, corrosion-resistant steel and extruded aluminum.
The batten 1 has a generally 4-sided shape wherein the side that shall be used to face the cladding wall panel is identified in the drawings as 2 and sometimes called “the front flange”; the side to face the inner wall panel is also identified as 4 and sometimes called “the rear flange”, and hence the sides that shall face into the wall cavity are also defined. (Of course the batten could be used the other way round—with flange 4 in contact with the cladding side). Those cavity-facing sides 3 are shaped in order that any water attempting to pass over the surface is (a) impeded, and (b) tends to arrive at drip-forming and flow-channeling means such that the water then flows out of the wall cavity under the influence of gravity and hence does not arrive at the inner wall panel. Each batten 1 according to the invention includes at least one of the following means to reduce or prevent the transfer of water from a cladding surface to any inner structure 30.
The battens shown in
Any feasible combination of the decorations to the sides of a batten as described herein may be used. The size or extent of the decorations is not important, so long as the are large enough to influence water movement yet not so large that they may contact the rear of the cladding panel (or perhaps spider webs or the like, that appear in time). Also, the decorations should not detract from the overall strength of the batten, serving as a cladding support means.
The battens may be formed by any economical method from any suitable material. In general the material should be relatively impervious to water, even though nylon (which takes up some water) would be acceptable. Sharpish outer edges help to control the water drops and make films into drops. An impregnated or wood, or a composite material based on wood should also be satisfactory, even though none of the drawings of sections through battens show an appropriate profile for a solid member made for example of wood. Paraffin wax is an example impregnating material. Example methods for manufacture include casting, milling, extrusion (as for plastics or some metals such as aluminum) or rolling a strip made of metal sheet, perhaps in more than one pass. Preferably a galvanizing, paint or other surface anti-corrosion protection is applied after rolling. In the case of hollow battens, fastening is preferably made through pre-formed holes into the support structure 30, and then the second panel is fastened to the batten most likely blindly or through drilled holes, so that the batten should be able to receive penetrating fasteners such as self-tapping screws or the like. Preferably each batten is sufficiently long that a single one will cover a wall, such as 3 to 4 metres long, but should allow for end-to-end contact and alignment so that the ridges carrying drips downward are aligned.
The system of the invention also provides a thick water-diverting layer for use in, or comprising a cavity wall. Preferred slab materials include expanded polystyrene, other structural plastics preferably foamed plastics, concrete such as a lightweight concrete as long as the material is capable of being formed with channels and slits within the slab. The material may be at least in part water-permeable.
Preferably the slab is from about 20-30 mm to about 400 mm thick and includes a series of channels that are formed a minimum of 10 mm into the slab from the front face of the slab. See, in particular
The mass of expanded polystyrene (EPS) is preferably selected from the available range of densities after expansion so as to be substantially impervious to the transfer of moisture. The “HD” grade (moderately dense though not as dense as geotechnical grades) is preferred, although any grade will do. The more water-permeable grades may be enhanced with a non-permeable coating on the face 72 which lies against the inner structure 30 of the building, opposite to the outer face 71 bearing the slits and opposite to the cladding.
The principle of this aspect of this cladding system for buildings invention is to implant a parallel series of relatively wide internal channels within the mass of EPS. Each channel of the example slab has a relatively narrow slit to the exterior along one side. Capillary action through the corresponding narrow slit will tend to draw any free water into the internal channel. Hence the slab acquires a preferred use orientation, in which the channels run vertically.
Prior art: It has been noted that U.S. Pat. No. 6,247,874 teaches a draining strap for use in drying soil in a garden or field, using a similar principle. This draining strap is somewhat flexible and can be laid down into the soil. U.S. Pat. No. 5,615,525 teaches a similar construction for “below-grade” lining of basements, wherein panels of the material are placed in the soil around a basement and serve to remove water from the soil into a drain so that the basement does not get so damp. U.S. Pat. No. 5,056,281 teaches a similar type of channeled EPS, for the same application as U.S. Pat. No. 5,615,525.
None of these specifications suggest use of an EPS draining panel installed within a building wall including a cavity space, with objective of channeling water that may appear within the cavity or the slab, where the EPS incidentally also has the advantage of serving as thermal and/or acoustic insulation, may support an external finishing plaster coating, giving a monolithic appearance, and provides structural rigidity and supports the cladding wall. Indeed, EPS slabs when installed may provide sufficient bracing for the wall to surpass earthquake-resistance requirements. One way to make this drainable EPS is to use a “mole plough” design of hot-wire cutter—or a series of such cutters—to melt the continuous channels and slits into a slab of EPS.
The channeled EPS slabs can be used to create a virtual cavity without battens in a wall, to define and fix the dimensions of the cavity, or may be spaced apart from the cladding panels by a small amount. In a preferred method of use, the slabs could be glued or otherwise fastened onto the interior support wall at the time of installation, or glued to the frame of studs and nogs, or on to the water-resisting membrane. Fasteners may be used. Further water resistance is obtained by using one layer of channeled EPS slab on top of another layer of channeled EPS slab, with the joints staggered so that there is no direct path for water between the cladding panels and the interior walls of the building.
The sill flashing 90 has a sloping sill platform 91 over which a finishing plaster 88 can be applied. Any water entering a crack between the plaster 88 and the joinery 86 will be resisted in the first instance by the vertical up-stand 92 of the flashing, which sits behind the joinery section 86. However, should a storm be particularly strong, forcing water in and over the top of the vertical up-stand 92, the moisture will then drain by gravity down into the collection channel beyond. This channel has a floor 94 and two side walls 93 and 95. The side wall 93 abuts the support structure and laps up behind a sill tray flashing 98 above, thus protecting the structure 30 from water damage. The side wall 95 connects the sill platform 91 to the channel section that is fixed to the structure. This side wall 95 also leads the infiltrating water to the floor 94 of the channel without contacting adjacent materials. The water can then exit the channel through apertures 96 formed in the channel floor 94, and subsequently exits the cladding system by flowing downwards through the cavity 7 behind the cladding sheets 40, which are supported off the structure 30 by the vertical battens 1. Also, in
The invention provides an acceptable and cost effective method of creating a cavity system about a new or an existing structure yet of overcoming the tendency of water to travel into the structure.
Unlike other battens, those of this invention may be located in order to suit the dimensions of prefabricated cladding panels. They also determine the thickness of the cavity of the cavity wall.
Battens according to the cladding system of the invention are capable of minimising the inwards migration of water, yet of maximizing the diversion of water downwards into draining means discharging it safely from the cladding system with virtually no risk to adjacent moisture and rot sensitive materials (of the support structure)
Draining slabs according to the cladding system of this invention are (a) capable of minimising the inwards migration of water, and of maximizing the diversion of water downwards and beyond the cladding envelope, and (b) are capable of serving as structural elements, by (a) supporting cladding means, and (b) providing bracing, if adequately fixed to the underlying interior structure.
Said draining slabs can be added to existing buildings, if the outer cladding is taken off, so as to reduce moisture admitted into the building, or to render existing buildings compatible with new regulations concerning moisture resistance.
Finally, it will be understood that the scope of this invention as described and/or illustrated herein is not limited to the specified embodiments. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth in the following claims.
Claims
1. A cladding system for an exterior wall of a building, characterised in that the cladding system provides a combination of physical, passive means within a cavity underneath the cladding of the wall, the means capable of at least partially obstructing the movement of water across the cavity towards an internal, water-susceptible structure of the building, and means capable of at least partially causing the water to flow out of and be expelled from the cavity, thereby protecting the internal, water-susceptible structure from water.
2. A cladding system as claimed in claim 1, characterised in that the cladding system is comprised of a plurality of elongated, substantially impermeable members herein called battens, each batten having a first surface for receiving an exterior cladding panel and a second, opposed surface for mounting upon the underlying inner structure, the surfaces of the batten being separated by at least one side surface bearing water path diverting means, so that when in use in a substantially vertical orientation, Water drops, films or droplets attempting to pass towards the internal structure are intercepted and encouraged to flow downwards and out from a base of the wall.
3. A batten for a cladding system as claimed in claim 2, characterised in that the water diverting means comprises at least one longitudinal fin, so that when in use the fin acts as a barrier to moisture migrating across the side surface, creating a pocket between the fin and the cladding panel comprises an open channel; thereby creating a path for water flow.
4. A batten for a cladding system as claimed in claim 2, characterised in that the water diverting means comprises at least one longitudinal everted edge.
5. A batten for a cladding system as claimed in claim 2, characterised in that the water diverting means comprises at least one longitudinal inverted valley.
6. A batten for a cladding system as claimed in claim 2, characterised in that the water path-diverting means comprises at least one series of elongated, slanted surface modifications, each surface modification being slanted towards the cladding side at a lower end, so that, when in use, water is guided by the slanted orientation of the surface modification downwards and towards the cladding side of the batten.
7. A batten for a cladding system as claimed in claim 6, characterised in that the or each surface modification comprises an elongated raised dome.
8. A batten for a cladding system as claimed in claim 6, characterised in that the or each surface modification comprises an elongated depression.
9. A batten for a cladding system as claimed in claim 6, characterised in that the or each surface modification comprises an elongated aperture.
10. A horizontal batten for a cladding system as claimed in claim 2, characterised in that the horizontal batten includes at least one longitudinally sloped side so that, when in use, the slope is oriented downwardly and outwardly away from the internal structure so that water is diverted in a direction away from the internal structure and towards a drain.
11. A horizontal batten for a cladding system as claimed in claim 10, characterised in that the horizontal batten includes intermittently spaced passageways at the intersection of the downwardly sloping side and the first surface, to allow moisture to egress past the horizontal batten when in use.
12. A cladding system as claimed in claim 1, characterised in that the cladding system comprises at least one mass of a water-permeable material, inside which a plurality of parallel, continuous, elongated drainage channels are made.
13. A cladding system as claimed in claim 12, characterised in that the cladding system comprises at least one mess of a material inside which a plurality of parallel, continuous, drainage channels are made; each drainage channel being substantially vertical when in use.
14. A cladding system as claimed in claim 12, characterised in that the cladding system comprises at least one mass of a material inside which a plurality of parallel, continuous, drainage channels are made; each channel being accompanied by a corresponding narrow elongated slit.
15. A cladding system as claimed in claim 12, characterised in that the cladding system uses a plurality of masses as an array of substantially rigid slabs; each slab having a first surface for receiving a cladding sheet, panel, or finishing surface and a second, opposed surface for mounting upon an underlying structure; each slab containing at least two continuous parallel internal channels.
16. A cladding system as claimed in claim 12, characterised in that the cladding system uses a plurality of masses as an array of substantially rigid slabs; each slab having a first surface for receiving a cladding sheet, panel, or finishing surface and a second, opposed surface for mounting upon an underlying structure; each slab containing at least two continuous parallel internal channels, each nearby and connected at least intermittently through a slit to the first surface.
17. A cladding system as claimed in claim 12, characterised in that the plurality of parallel, continuous, drainage channels, when viewed in plan, are configured so that they form at least one series of at least two channels, substantially parallel to the first surface of the cladding sheet.
18. A cladding system as claimed in claim 17, characterised in that the plurality of parallel, continuous drainage channels, when viewed in plan, are configured so that they form at least two series of at least two channels, whereby the channels of one series are offset with, or to, the channels of an adjacent series; so that any imaginary line projected perpendicularly from any point on the first surface, will cross or be intercepted by at least one drainage channel.
19. A cladding system as claimed in claim 14, characterised in that each substantially rigid slab employs capillary action through the slit to draw water from the first surface towards the internal channel, which, when oriented in an at least partially vertical direction, is capable of conveying the water towards a lower end of the channel.
20. A cladding system as claimed in claim 14, characterised in that each substantially rigid slab is provided with an array of slits and corresponding channels emerging on to more than one surface.
Type: Application
Filed: Mar 28, 2008
Publication Date: Jun 17, 2010
Inventor: David Peter Dickinson (Auckland)
Application Number: 12/450,482
International Classification: E04B 1/70 (20060101); E04B 1/64 (20060101);