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Page | 26 GUIDE TO THE SPECIFICATION, INSTALLATION AND USE OF PRESERVATIVE TREATED ENGINEERED WOOD PRODUCTS Damp proof course strip above H3 treated LVL deck joists to isolate from decking and weather (Maryborough) Courtesy Stephen Bolden Roof overhangs are regarded as particularly useful in providing physical shielding of buildings from the weather. The building zone in side the 30˚-fromvertical line under a roof overhang is commonly accepted as being protected from weather exposure (i.e. H1/H2 when above ground). One of the most common and easiest forms of shielding is the application of damp proof course (DPC) above decking joists and under the decking boards. This relatively simple measure can add at least 5 to 10 years to the service life of exposed decking joists. Isolation Isolation of EWPs involves separation from moisture sources, moisture traps, or direct contact with other exposed or potentially damp members. Isolation of members or connections can be achieved by: Building in air gaps to prevent bridging of water Damp-proof courses Sarking Drainage EWP members and connections should always be designed to allow free drainage of water. Where possible slope or profile top Figure 8: Back cut rafter / beam overhangs Naturally durable hardwood Glulam post isolated from ground (Courtesy Holmes McLeod) Figure 7: Isolation of Timber from Moisture Traps Reference: Timber Service Life Design Guide, FWPA 2007
Treated Glulam and plywood structure isolated from ground (Courtesy Harry Greaves) Figure 10: Slope horizontal members GUIDE TO THE SPECIFICATION, INSTALLATION AND USE OF PRESERVATIVE TREATED ENGINEERED WOOD PRODUCTS surfaces or provide drainage holes to prevent water sitting on the surface. Ventilation Ventilation is essential to prevent moisture accumulation from a variety of sources including rain, leaky plumbing, rising damp from foundation soils and condensation. Rising damp under sub-floors is handled by building regulations which specify minimum cross-flow ventilation. Figure 12: Beam capping / end flashing Figure 9: Drainage holes Reference: Timber Service Life Design Guide, FWPA 2007 Figure 11: DPC to isolate joists Page | 27
Page 1 and 2: MARKET ACCESS & DEVELOPMENT PROJECT
Page 3 and 4: Publication: Guide to the specifica
Page 5 and 6: TABLE OF CONTENTS GUIDE TO THE SPEC
Page 7 and 8: GUIDE TO THE SPECIFICATION, INSTALL
Page 9 and 10: Figure 1: Design Process APPLICATIO
Page 25: Good design and detailing Design an
Page 29 and 30: Finishing of preservative treated E
Page 31 and 32: Special considerations GUIDE TO THE

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