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Using hardwood & cypress Processing
Log Products Log products involve the minimum amount of processing, and are commonly used for pole, pile or landscape applications. The sapwood of log products may be preservative treated to help meet durability requirements. This involves leaving the sapwood in place to accept preservatives, while in other instances – such as in power poles – sapwood is purposely removed (i.e 'de-sapped'). Basic types of log products are shown in Figure 3. Sawn Products Sawn products involve cutting logs into large slabs, then re-sawing into smaller sections. There are two main categories – backsawn and quartersawn sections (refer Figure 4) as well as a hybrid of the two. Each has a different effect on the way growth rings appear in the cut timber. As discussed later, this affects the appearance and manner of shrinkage in the timber. After sawing, joinery and visually exposed structural timbers are usually kiln dried and dressed to actual size. The same is true for lintel, truss and other framing elements requiring dimensional stability. Other framing timbers and certain types of cladding only require a 'sawn finish' (off the saw), and are generally unseasoned and nominally sized. Exceptions occasionally occur. Some unseasoned hardwoods and Cypress may be dressed when only partly seasoned. It is best to inquire with suppliers for specific products for intended applications. Nail Plated Timber Nail plated timber makes greater use of small and short timber sections. They are mechanically joined to provide increased length or depth. The timber pieces are generally kiln dried and machined to size before plating. The process is carried out as a manufacturing operation to ensure the quality of jointing. As the nail plates are exposed, these elements are usually used for structures that are concealed from view. The nail plates may be affected by exposure to weather and should only be used in protected locations. Engineered Timber Products Engineered timber products offer the most advanced usage of raw timber. A common example is glue laminated beams which use small timber sections glued together as shown in Figure 6. The benefit of this approach is that natural imperfections in the timber can be significantly reduced – creating a stronger, straighter, and more stable product – compared to sawn timber. In addition, large beams can be produced to suit standard or customised structural situations. For instance, beams can be produced with curves, tapers and cambers to suit specific needs. Advanced elements include portal frames and arches. Sheet timber products and veneers Sheet timber products and veneers take a different approach to utilising the raw material. Plywood and decorative veneers are made by peeling or slicing logs. Peeling is usually for structural purposes and slicing for decorative. Plywood involves gluing layers on top of each other until reaching the desired thickness. The knots and other imperfections are isolated into single veneers rather than continuous as per a solid product. The grain of each veneer is run in a perpendicular direction to adjacent layers. This creates strength in both length and width. Uses are mainly for formwork and decorative flooring. Decorative veneers have multiple fitout and furniture uses and are often overlaid on plywood or medium density fibre board. Another sheet application is hardboard. It is made of fine hardwood fibres held together with natural lignin from the wood – applied under heat and pressure. It is commonly used for cladding, bracing and is also used for linings (especially where sheets are perforated to reduce noise). |
