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Proper installation, care and maintenance will ensure you get the best performance from your deck. These recommendations should be read in conjunction with NZS3602, NZS3604, NZS3605, NZS3640, NZS4203 and BRANZ Bulletin 489 and any relevant Territorial Authority requirements.


Ventilation Free air circulation under the decking is very important to help minimize cupping and warping for any timber. Proper ventilation ensures the potential difference in moisture levels between top face and the underside of the boards is reduced and extends the life and performance of the deck. The sub-deck should be greater than 450mm clearance from the ground and should also have adequate drainage. This, in conjunction with suitable spacing, will allow for adequate ventilation.

It is important that the perimeter of the deck is not fully enclosed by a surround, and remains open to airflow. Completely enclosing the sides of the deck will inhibit proper ventilation and compromise the performance of the decking. In wet areas or over water, additional clearance is recommended.

Failure to provide for suitable ventilation is a major cause of early decking failure.

Other steps that can be taken to minimize moisture differential are:

  1. A ground level vapour barrier (with slit drainage).

  2. A suitable surface coating on all four sides of the decking boards (refer coating section).

Span Hardwood Decking, 19mm thick should be installed at maximum 450mm joist centres.

The joists should be clean and sound and the screws should penetrate at least 40mm into the joists to achieve good holding. Pre-drilling and counter-sinking is essential to avoid end splits.


Decking must be kept dry and out of the Sun and Rain. Storage of decking should be kept in a covered, cool and dry place. On site each pack should be kept at least 100mm off the ground by placing it on bearers. Make sure bearers are evenly placed to support the load of timber. Do not leave it on the shipping pallet.

Using a plastic tarp isn’t considered best practise while storing your decking timber. If you cannot store your timber in your garage or under a roof, use a canvas/waterproof tarp and allow ends to be open for air flow.

End sealing

End sealing will help minimize splitting and checking at the ends of the boards. We recommend the boards be end-sealed with a quality penetrating oil as soon as possible after cutting and before final installation.


Oiling or applying a protective coating to your decking timber is typically done as part of regular maintenance to enhance its durability and appearance. The timing for oiling coat your decking timber can vary depending on several factors, including the type of timber, weather conditions, and the previous coating’s condition. Proper coatings can vastly decrease the maintenance required on your decking. Boards should be free of all surface marks and stains before coating. It is recommended that a “clear” decking oil is used.

We recommend prior to installation coating all four sides of your Hardwood boards with a quality decking wood oil. This will help preserve and protect your timber and reduce potential cupping and checking by slowing moisture transference in and out of the timber. Purpleheart does not need to be oiled and can be left to weather and silver off.


In average New Zealand climatic conditions, decking will expand and contract during the seasons. Decking will need extra spacing or gaps, to allow for expansion as the decking takes in ambient moisture. If laid too closely the deck will swell and possibly lift off the joists. In average New Zealand climatic conditions 140 x 19 & 145 x 21 decking should be spaced 6mm apart. The specified gap for each size will allow the deck to drain and allow air circulation under and around the decking.


These are recommendations only. An allowance for regional climate conditions should also be factored in. Fastening Screws are essential for 140x19mm decking. We recommend T316 65-70MM Star head screws through the pre-drilled and countersunk face of each board, two per joist 15-20mm from the ends and edges. Care should be taken not to over-drive screws. Pre Drill pilot holes slightly smaller than the screw and countersunk.


Cleaning & Washing

Hardwood decks should be cleaned with a stiff brush at least once a year to clear gaps and remove surface mould which can be a slip hazard in wet weather. It is also important for the life of the deck to keep it clear of leaf litter.

Place your pot plants and other large objects on raised “feet” to allow the decking under them to dry out.

Hardwood decking can be water-blasted BUT it is important to do so at a low pressure so as not to damage the fibers of the board by going too hard and/or too close. Care must be taken not to stop at the end of the stroke but to lift the nozzle away when changing direction.

Washing the deck

Brush the deck with a mild solution of Janola and water (1:16), or suitable equivalent. This will remove any build-up of resin or extractives that may leach out of the timber as the pieces “season” in situ. There are also various chemical cleaning agents available, from detergents through to acids. Follow manufacturer’s instructions and be conscious of the run off as this will depend on the specie, how dry it is before the decking is laid and how exposed the deck is to weather.


Always follow the paint manufacturer’s specification for re-coating.


Our Hardwood Decking is sourced, milled, transported with care and finally inspected to ensure quality. As with all natural wood product it is subject to variations in weight, density, colour, grain and performance. Care must be taken at installation and maintenance to allow for movement. Some swelling, shrinkage, movement and checking are normal occurrences in timber decking.


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