Lumberbank Product Installation Guide

Decking Guide Installation and care

Whether you’re a professional builder or like to DIY, you’ll get a longer life from your decking if you follow these few simple steps.

Two types of timber – your choice

the best condition for building a long-lasting and secure deck.

Lumberbank distributes a number of species of hardwood decking. These come in two conditions – kiln-dried and ‘green’. Both types need careful handling to get the best from your deck, but there are a few differences in the spacing.

Standards and Local Authority requirements

Kiln-dried hardwood

You can reduce later maintenance and increase the life of your deck by coating your timber before you build. Sealing the ends stops splitting and checking, and should be done first thing – even before you store the timber on site.

This timber has less than 18% moisture content after kilndrying, and will expand slightly in NZ weather conditions.

You’ll need extra spacing during installation, to allow for the timber taking on water from the surrounding air. If the timber is laid too closely, it may close up, warp or loosen as it expands.

‘Ship dry’ (green) hardwood

This timber, being green, will shrink slightly as it slowly dries after being installed. We recommend leaving a 2mm space for both 90mm and 140mm widths.

Before you start building Taking care right from the start means your timber will be in

Be sure to read NZ3602, NZ 3604, BRANZ Bulletin 489 and all relevant local authority building regulations. Obtain any necessary consents before you start.

Treating the timber

Coating – on all four sides – is the best way to slow moisture transference and maintain the colour and shape of the timber after installation. Make sure your boards are clean and free of stains before you apply the coating. We recommend that you use a ‘clear’ decking oil.

Storage – dry and off the ground

Keep your timber dry and shelter from the weather until you’re ready to use it. Stack it on bearers to keep it off the bare ground, and cover it securely.

Installation: strength and ventilation Here are some ‘tricks of the trade’ for installing the best deck.

Clearance from the ground

An important aspect of good deck building is making sure air can circulate under, over and through your decking. That way, the natural moisture exchange of either type of timber happens evenly over the whole deck, and you avoid the cupping and warping of uneven drying rates.

You should plan to build your deck at least 450mm from the ground. Make sure the surround of the deck is not completely enclosed, to allow for free air movement. If you are building the deck over water, your clearance needs to be even higher. You can also install a ground-level vapour barrier with slit drainage.

Span – for optimum strength

We recommend maximum joist centres depending on the thickness of your decking – for 19mm set joists no further apart than 450mm. If you’re using 32mm decking, you can increase the joist centres to 600mm.

If you are using nails on 90mm timber, choose 60mm nails with annular grooves.

Looking after your deck Timber decking changes over time and seasons, so it’s important to maintain it regularly so it lasts a long time.

Cleaning with a good stiff brush

Give your hardwood deck a sweep with a stiff broom at least once a year (more often if you live near trees), to get rid of leaf litter and slippery surface mould, and clear those all-important gaps. Move and sweep under any furniture or pot plants that could hold moisture against the decking.

Water-blasting – on low pressure

You can waterblast your deck, but too high a pressure or blasting too close could damage the fibres of the wood.

Don’t stop at the end of a stroke, just lift the nozzle away when you’re turning.

Chemicals – good and bad

Radiata pine joists should be clean and sound, and screws should penetrate at least 40mm for a solid fix. Pre-drill and counter-sink your hardwood timber to avoid splitting the ends.

Your deck can be washed down with a 1:16 solution of chlorine bleach, to remove any leaching resin or extractives that appear as the timber seasons. Other cleaning agents are available, so follow the manufacturer’s instructions for use, but be aware of run-off. This will depend on the type of decking, how dry it was when laid, and weather exposure.

Spacing – for air and drainage

Re-coating

Spacing is important as the ‘green’ timber dries, or as the kiln-dried timber takes on moisture. It’s also important to allow the deck to drain after rain, and not capture pools of water that will damage the timber.

As it seasons, your deck may need re-coating from time to time. Be sure to follow the manufacturer’s instructions for any re-coating product you use.

For 90x19mm kiln-dried timber, leave a 4mm space, and for 140x19mm, leave 6mm. For ‘green’ hardwood, leave a 2mm space for both 90mm and 140mm.

Disclaimer

NB: These are recommended spacings, and don’t allow for regional climate conditions.

Fastening – screws are recommended

We strongly recommend that you use screws to fix your decking in place, and if you are building with 140mm timber, screws are essential. Pre-drill two holes through the face ends of each board 20mm from the edges, and use 60mm stainless steel screws to fix them to the joists. Be careful not to over-drive the screws.

Lumberbank suppliers takes every care in the manufacture of hardwood decking timber. However, it is a natural product and varies in colour, grain, weight, density and strength. Take care during installation and maintenance to allow for shifting.

Expect some checking, shifting, swelling or shrinkage in your timber decking.

NB: Lumberbank does not endorse the use of hidden fixing systems with our decking products at this time.

Contact us 0800 458 623 09 622 2050 sales@lumberbank.co.nz