Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Name of Applicant: ANDREW PETER BEATON Actual Inventor(s): ANDREW PETER BEATON Address for Service: SANDERCOCK & COWIE 180B SLADEN STREET CRANBOURNE VICTORIA 3977 Invention Title: PLASTIC SUB-FLOOR DECK FLASHING - 1 - - la TITLE: PLASTIC SUB-FLOOR DECK FLASHING FIELD OF THE INVENTION 5 This invention concerns flashing for timber constructions especially the sub-floor structures of dwellings. These structures support decks, external patios and verandahs. BACKGROUND OF THE INVENTION 10 Decks are generally subject to weathering and are consequently built of softwood treated -2 to withstand decay with a hardwood as the finishing timber which withstands impact better than softwood. Native hardwoods and imported hardwoods withstand pedestrian traffic, dropped implements and the wheels of children's toys, better than softwood. All decay eventually due to the effect of rain. Rain leaches out water soluble preservatives 5 and encourages the incursion of fungus which feed on the cellulose in the timber. The joists and bearers are in mutual contact and the joints are in contact with the decking which receives most rain. Thus an unbroken moisture path leads from the decking through to the lowermost part of the structure. 10 The timbers dry out but the sites which do not dry completely are at the timber crossover sites. The thinner decking strips which may be 18-19mm thick dry relatively quickly but the thicker joists and bearers are slower and contact sites stay wet longer. 15 SUMMARY OF THE INVENTION An apparatus aspect of the invention provides a flashing comprising a strip of water impervious thermoplastic polymer having a pair of parallel edges and a margin inboard of each edge which margins define a central planar band and in use incline downwardly 20 in relation to the central planar band in order to shed water. The inclination may be 200-70', preferably 40'-50'. In practice, extrusion error may cause the margins to undulate somewhat but the purpose 25 is to drain the timber/flashing boundary. The strip is 55-116mm wide, preferably 50 70mm wide. The thickness of the flashing may be 0.8-1.5mm thick. The margins may be 3-12mm wide. The polymer may be polyethylene filled with carbon but polypropylene and similar polymers and copolymers will perform suitably. These are in the building literature. 30 A method aspect of the invention provides a method of building a timber structure incorporating the flashing, comprising applying the flashing to a lower supporting timber -3 member lying in a first direction by covering the upwardly facing side of the member with the flashing and overlaying a portion of the flashing with an upper supporting or finishing timber member lying in a second direction transverse to the first direction and securing the upper member to the lower member and repeating the sequence. 5 The upper member may be a decking strip. In a lower stage of a deck, the flashing may be laid across two bearers paired side by side. A further apparatus aspect of the invention provides a flashing for weatherboards, 10 comprising a strip of water impervious thermoplastic polymer of L-section, wherein the leg when in use is horizontal and ends in a margin which is inclined to the leg in order to shed water. The horizontal leg may be 45-50mm wide and the margin is 3-8mm wide. The thickness 15 may be 0.8-1.5mm. BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention is now described with reference to the accompanying 20 drawings, in which: Figure 1 is a sectional view of the flashing suitable for a 45mm thick joist. Figure 2 is a sectional view of a wider flashing suitable for a sistered joist 45 + 45mm 25 wide. Figure 3 is a sectional view of a weatherboard flashing. Figure 4 is a diagram of a wooden structure showing incorporation of the flashing. 30 -4 DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS Referring now to the drawings, the narrow flashing is extruded from a die as a continuous molten strip with a flat part 2, 48mm wide with two margins 4, 8mm wide disposed at 5 45'. The strip is 0.8mm thick. The strip is chilled in cold water straight after extrusion which assists the strip in asserting the profile shown. This is retained when the strip is wound in a coil for transport and storage before sale. In Figure 2, a version 100mm wide also has like margins of the same width and 10 inclination. In Figure 3, an extrusion of L-section has an upright leg 6 and a horizontal leg 8, both 40mm in length. Horizontal leg 8 has a margin 4 also disposed at 45'. This protects the horizontal batten fixed to studs in order to incline the topmost weatherboard in a timber 15 wall. In Figure 4, a pair of bearers 10 are covered by the flashing shown in Figure 4. The joist 12 is toe nailed to the bearers. Joist 12 is covered by the flashing shown in Figure 1. Decking strips 19mm thick are nailed to the joist. 20 I have found the advantages of the above embodiments to be: 1. The rain soak path through the structure is reduced to 19mm, namely the thickness of the decking. 25 2. Rain shed by the narrow flashing drips onto the lower wider flashing and is in turn shed. It is to be understood that the word "comprising" as used throughout the specification is 30 to be interpreted in its inclusive form, ie. use of the word "comprising" does not exclude the addition of other elements.
-5 It is to be understood that various modifications of and/or additions to the invention can be made without departing from the basic nature of the invention. These modifications and/or additions are therefore considered to fall within the scope of the invention.