Home

Treated Plywood

Home » Treated Plywood

Protecting plywood
Plywood may be subject to decay and/or termite attack under certain conditions. In-ground applications can cause both decay conditions and termite attack. Correct preservative treatment against fungal attack, or rot, is essential for all plywood, either painted or unpainted, that is to be permanently exposed to the weather.

Infestation with termites is usually not a problem for plywood when used in above ground applications.

When should plywood be treated?
Plywood can either be treated by impregnation of veneers, prior to manufacture or by pressure treating manufactured plywood. Pressure treating plywood is an 'envelope treatment' only, treating the outer veneers, edges and ends of sheet. The preservative may not penetrate through the glue lines to the middle veneers. If plywood is cut, then localised paint on preservative treatment is required to the cut edge. This treatment is only practical for thicker panels.

It is important to note that preservative treating after manufacture or surface treating with 'brush on' preservatives should be done only after machining, sawing and boring has been completed. Some preservation treated plywood will be difficult to bond, particularly if phenolic or resorcinol adhesives have been used.

Preservative treated plywood is suitable for painting provided manufacturers recommendations are followed.

Plywood treatments
A range of preservative treatments are available for plywood including CCA (copper chrome arsenate), LOSPs (light organic solvent preservatives) and for veneers, Ruply and ACQ (Alkaline Copper Quaternary Compounds).

For building construction, the most suitable treatments are CCA and LOSP.

Plywood with a Type A bond used as exterior cladding must be treated against fungal and insect attack. This should be with a minimum of hazard level H3 for 'outdoors above ground' as per AS/NZS 1604.3.

Most softwood species can be treated with non-leachable preservative salts, which will impart decay resistance. The level of preservative treatment specified for softwood laminated beams used in Service Class 3 applications should be H3. Similarly LOSP envelope treatment can be used satisfactorily. It is always best to check with the manufacturer for recommended use.

Ongoing maintenance and inspections will help to make sure rot/infestation does not occur in structural above-ground applications.

Learn more
You can find out more detailed information about plywood here.

Cladding, External

No other cladding material can offer the design freedom, ease of handling, range and natural beauty of timber. Timber cladding can create a building to suit almost any environment, taste or style.

Timber cladding has an inbuilt flexibility that provides natural advantages on sites subject to high winds, extreme climate, highly reactive soils, subsidence or earth tremors. And unlike masonry and other rigid materials, the natural resilience and high strength to weight ratio of timber enables it to withstand far greater stresses and movement.

Modern finishes give a long lasting and attractive appearance to timber cladding and can be used to change the colour and style of the building, making it a versatile material that will keep pace with changing tastes and fashions.

 

Framing

Lightweight timber construction typically comprises framed and braced structures to which one or more types of cladding are applied. Framing configurations can range from the closely spaced light timbers commonly seen in stud frame construction to large, more widely spaced timbers. A timber framed building can be placed on a concrete slab or on posts/poles or bearers resting on piers/stumps supported on pad footings.

Used in houses or multi-residential dwellings, lightweight timber construction offers the flexibility of a wide range of cost effective design options.

When the timber comes from sustainable sources, this construction method can be environmentally advantageous as it combines timber's low embodied energy with its capacity to store carbon.

Joinery

Timber joinery products offer a classic, unique and stylish touch to any interior or exterior design. The products are produced for a variety of internal applications including door and window frames, cabinetry, skirtings, mouldings and architraves. When looking to the outdoors, joinery products range from decorative eaves and posts to eye-catching railings.

Many timber species are suitable for joinery products and care should be taken in selecting the perfect timber for the particular product and its intended finish. Rare and exotic species such as Teak and Rosewood can generate pieces of outstanding beauty but material cost and availability are also important considerations.

Commercially available species like Tasmanian oak, Australian cypress, spotted gum and the like, often make the more practical choice, with the added benefit that they can be easily matched with other timber products within the building, like flooring.

Solid timber for joinery products is generally supplied as ‘clear finish grade' but ‘paint grade' options are available and these are usually comprised of a composite material like MDF or glulam.

A large number of specialist suppliers and producers offer the consumer extensive choice of profiles for all of the most common and popular joinery products. Choice is in many cases, limited only by imagination.

Cabinetry is often associated with joinery and most typically includes, cupboards, benches and other similar ‘built in' furniture. Like joinery, cabinetry is generally specified as either paint or clear finish grade and naturally for clear finish grade timbers, appearance and surface finish are critical in achieving a successful application.

 

Portal Frames

Timber portal frames are one of the most favoured structural applications for commercial and industrial buildings whose functions necessitate long spans and open interiors. As a material choice, timber offers designers simplicity, speed and economy in fabrication and erection.

Timber portal frames offer a strong, sound and superior structure. Structural action is achieved through rigid connections between column and rafter at the knees, and between the individual rafter members at the ridge. These rigid joints are generally constructed using nailed plywood gussets and on occasion, with steel gussets.

From material selection to finishing, this application guide provides a comprehensive overview of the process of using timber in the specification, fabrication and erection of portal frame structures.

Shear walls

Framed timber buildings, of post and beam or stud and joist construction, resist lateral loads (wind, earthquake or impact) by using rigid frames (portals), braced frames (trusses and cross-bracing) or structural sheathing elements (diaphragms).

Diaphragms are an efficient structural solution to resist lateral forces. The sheeting materials that are generally used as lining or cladding can usually be upgraded to resist shear loads, easily and economically. The framing then performs dual functions, resisting both horizontal and vertical loads.

In cases where diaphragms comprise structural sheathing, additional design efficiencies can be incorporated to resist loads normal to walls, floor and roofs using the composite stressed skin action developed between the sheathing and the timber frame.

The advantages of timber shear walls and diaphragms include:

  • architectural design freedom (curves, cantilevers, clear spans) 
  • lightweight construction 
  • high impact load resistance 
  • resilience (no brittle cracks) 
  • fast conventional construction 

In this section you'll find information about the design and construction details of timber framed diaphragms (both horizontal and vertical) used in domestic, low rise commercial and industrial buildings.

Framing design for dead loads, or dead and live loads acting normal to the framing are covered in AS 1720.1 Timber Structures and AS 1684 Residential timber-framed construction. To develop efficient diaphragm action, some adjustments, particularly connection details, are usually required.

Information about diaphragm materials and systems is included, however the majority of the design and construction details provided herein are for structural plywood diaphragms for which documented design information is available.

Stairs, Exterior

All exterior stairs serve a functional purpose, but the choice of timber in the application will turn a functional building element into an aesthetically pleasing feature. And while the construction of stairs is demanding, the investment of time will be returned, with a well constructed timber staircase typically lasting decades.

Exterior stairs are usually built from treated softwood and durable hardwoods and typically finished with paint. The construction procedure described here applies to most general type stairs of either conventional or contemporary construction.

When it comes to stairs there is a multitude of variations available for application depending on the structural requirements of the building. This guide discusses the most commonly specified stair types.

Are you looking for a supplier?