Select the correct materials for your deck and it will be strong and last for many years.

Choosing timber
The timber will be exposed to all types of weather. If you live in a termite-prone area it must also resist attack from termites.

Unseasoned timber will inevitably shrink, warp or bow. Most hardwood is only semi-seasoned when purchased, as fully seasoned is very difficult to work. Most treated timber, however, is seasoned.

Look for faults such as bowing or twisting. Lightly bowed or twisted timber may be flattened or pulled straight while it is fixed in position, but badly affected timber may be unusable.

Durability
Hardwoods have a high durability and can be used both in and out of the ground. However, it is recommended that any timber in direct contact with the ground be treated with a suitable preservative.

Any timber used in the ground will require a higher level of protection than that being used above the ground. Durability is rated as class 1, 2, 3 or 4 with class 1 having the highest durability and resistance to attack. Any hardwood placed in the ground must have a durability class 1.

Tip: Class 4 timber should not be used for weather exposed structural members such as posts, bearers, joists or decking unless it has been pressure treated.

Pressure-treated timber
The most commonly used timbers for decks are pressure-treated softwoods such as radiata or hoop pine. Preservative-treated softwoods are readily available from most timber merchants and are commonly treated with one of three preservatives:
CCA: copper chromium arsenic
ACQ: alkaline copper quart
LOSP: light organic solvent preservative.

The first two give a green tone to the timber while there is little or no colour change with LOSP. LOSP is less permanent and should be given a protective coating to prolong its life. Timber treated with this preservative is not suitable for use in the ground.

Treated softwoods are available in a range of hazard or `H' levels from H1 through to H6, with H6 having the highest level of treatment. Brush on preservative should be applied to all sawn or shaped surfaces.

Some treated timber may be water repellent, but it will still weather, turning silvery grey over time. A decking oil or stain will counteract this though it will, in turn, require some maintenance.

Precautions with treated timber:
Always wear gloves when handling treated timber.
Use a dust mask and goggles when machining, sawing or sanding.
Ensure there is good ventilation in the work area.
Wash your hands and face before drinking or eating.
Wash work clothes separately.
Never use treated timber for heating or cooking, especially on barbecues.

Stress gradings
Timber is also stress graded and given an `F' rating. The `F' rating is followed by a number, which indicates the bending stress of the timber. The higher the number the greater the stress the timber can withstand. Bearers and joists should normally not be any' less than F7; posts may be F11 if hardwood or F7 or better if seasoned softwood.

Hardware
Any deck is only as good as its fasteners. Most are made from mild steel with a protective coating and, in most situations, hot-dipped galvanising is the preferred coating.

Stainless steel fasteners may be needed where there are high corrosive conditions such as around saltwater pools or subject to sea spray.

Other metals such as brass and copper may be appropriate in some conditions, depending on the preservative used - check with your hardware supplier.

Machine or cuphead bolts hold structural members together more strongly by far than nails. Coach screws may be used where access is restricted to one side. Washers should be used on both ends of machine bolts and under the head of coach screws to prevent them pulling into the timber too far.

Masonry anchors may be required to fix ledgers to brick walls, or stirrups to footings. Use the appropriate size of anchor-if the anchor is too short the device may not hold tight; if it is too thin it may snap when subjected to stress.

The decking itself is subject to constant movement as it expands and contracts according to the weather and as people walk over it:
Galvanised nails with a spiral or twist shank are, accordingly, best for fixing it as jolt-head or bullet-head plain shank nails do not have as much holding power.

Jolt-head nails are satisfactory for the framework.

Tip: there are special decking screws available with countersunk heads but they are only needed under extreme conditions. A well-nailed deck will normally give long service.

Other metal timber connectors, such as nail plates, frame connectors and joist hangers are made from galvanised steel. There are many different types of connectors and they can be used for scores of different applications.
Post stirrups, or supports, and brackets are hot-dipped galvanised by the manufacturer. If they are cut or drilled for any reason, reapply a protective coat of galvanised paint.

Estimating materials
The plans of the deck that you have drawn up to submit to your local authority for approval will probably have to include detailed specifications and dimensions. These drawings will help when you come to estimate all the materials required for your deck Mistakes at this stage can be costly, as timber is expensive.

Use the materials and tools lists to make a checklist of all you'll need, deleting or adding to suit your deck. This will also help you cost the deck.

Ordering materials
Most timber merchants will help you order the correct quantities, grades and species of timber for your project just show them the plan.

Timber is sold in set lengths, starting at 1.8 m and increasing in multiples of 300 mm. A supplier cannot hold every length, and so you may need to combine lengths to avoid waste. For example, if 1.8 m joists are required and the supplier's lengths start at 2.4 m, there would be 600 mm of waste from each joist. However, the supplier may have 3.6 m lengths, in which case two joists could be obtained from each.

Decking may be purchased by the square or linear metre. Allow at least 10 per cent waste for cutting.

Storing timber
When timber is delivered to the job, keep it off the ground, to prevent it being affected by rising moisture and keep it covered from rain. Moisture can cause it to warp or split. Keep the stack out of the way so it doesn't interfere with the smooth flow of the job.

Source: Building Decks (Murdoch Books) Mini Workbook Series $4.25