Building a Timber Deck
Hardwoods for decking include kwila, vitex, western redwood, jarrah, and garapa. Each has a signature look. For example kwila is a deep red-brown colour, while vitex weathers to a silver-grey. It is a matter of personal preference, what you can afford, and your wish to support sustainable forests.
You will need to know your Decking Terminology:
- Oversite = area under the deck; should have slope 1 in 40 for drainage.
- Footing / Piling/ Pier/ Deck Post- concrete and beams that supports the deck
- Ledger Board= Beam secured to building to support deck structure.
- Beam= The main horizontal timbers of the deck (support the joists). Usually a pair attached to either side of the support post.
- Joist= Multiple horizontal timbers that support the deck boards.
- Deck Boards/ Decking= the floor of the deck
- Newel Post= Vertical post that supports balustrading.
- Balustrading= Vertical railing secured between newel posts as a feature or barrier.
- Baluster Rail= Top and bottom rail sections of balustrade to which spindles are fixed.
- Baluster / Spindle= Vertical railing
- Hand Rail= Top rail section of balustrade.
- Stair Stringer = An inclined piece that supports stairway tread.
- Fascia= attached along deck’s outside edge for tidy appearance.
Deck ventilation is important. Allow for 450mm clearance from the earth, and use suitable board spacing. Deck board spacing ranges from 2mm to 6mm, and depends upon the wood used and how it has been dried. Consider adding a ground level vapour barrier with slit drainage to keep moisture from the ground to a minimum.
Regarding spans, 19mm decking should be installed at maximum 45mm joists centres; 32mm decking can be on 600mm joists centres. Choose the direction you wish to lay the deck boards — this will establish joist direction.
Screws should be of a length so that they penetrate at least 40mm. Stainless-steel screws will resist corrosion and extend your deck’s life. Electroplate-galvanized screws, though widely used, are not acceptable for decks. Nails are never the ideal choice. Think about if you want the screw heads to be hidden from view.
Do you want to have access under the deck? Be sure the access door is wide enough to easily accommodate mowers, wheelbarrows, etc.
Will you have a hot tub on the deck? If so, be sure the deck can handle the weight.
Other amenities (lights, speakers, irrigation, etc.) should be taken into consideration so that wiring and hoses can be hidden from view.
Treating or staining of the deck should be done twice in the first year, then periodically after that as per the manufacture instructions. CD50 Extreme Decking Oil is an example of a product that will stain and protect a wooden deck. It is recommended to choose a lighter colour stain– this gets less hot in the sun and as a result your deck will last longer.
Caring for your deck includes keeping it free of leaf litter, brushing with a hard brush once or twice yearly, placing potted plants on ‘feet’, and wiping up spills immediately. If you decide to water blast, use a low setting; do not stop when changing direction with the wand, but lift the nozzle. There are many commercially available cleaning products, but an easy homemade one is 250ml bleach added to 1 litre of water. Be conscientious of the run-off of any of these mixtures.
A deck must match your lifestyle and the architecture of your home.
How do you wish to use your deck? When considering the size and shape of your deck, leave room for a BBQ, prep station, drinks table, table and chairs, lounge chairs and a low table…whatever you think you may want. What about special features such as a pizza oven, brazier, water feature, sculpture or fresco? Use shapes other than squares and rectangles. Try a diamond, an oval, or a sweeping curve.
Use stakes and string to outline your deck’s footprint to visualize the deck and how much garden it will cover. Place furniture, the BBQ, etc. inside the outline to check clearance around everything. Make sure your dining table will fit comfortably: allow at least 1 metre all the way around the table so that people can walk behind those who are seated. Walk around to see if you like the shape, circulation, and views of the proposed deck.
The style of your deck and its fixtures (lights, fans, etc.) should match that of your home. Details such as railings can be wood, metal, glass, cabling, or vinyl. The railing could be a contrasting colour to the decking boards. Also think practicality: wide railings are useful places to set down a drink. Posts can be finished with trim at their base, or with capping on top. Inlaid accent boards in the decking can add amazing flair.
More than one level of deck is an interesting consideration. This can be a good way to deal with a heavily sloped site or to break up a long flight of stairs. But don’t let levels make too many tiny, unusable areas. Regarding stairs and safety, ensure good lighting (eg. riser lighting) and build stairs with a deeper tread and a lower rise than you would typically find with indoor stairs. Always add a hand rail where needed.
People are sometimes tempted to place a hole in their deck for a tree to grow through. I personally am not a big fan of this for the following reasons: the tree may get too large for the hole /space, the tree may be too close to the house, limbs from the tree will fall on the deck, leaves from the tree will litter the deck, the tree may not get enough water, the tree will eventually die. But if you MUST do it, leave enough room for growth and rainwater, and make sure the tree will not grow too close to the house.
Another thing I would avoid is built-in seating. It is rarely comfortable and cannot be moved…you are limited in how you can move your furniture around it.
For small spaces, aim for a one-level deck with no railings. If the height of the deck requires you to have a railing, perhaps it can be avoided by adding a set of stairs that run the width of the deck?
Decks in heavily shaded areas can quickly get a build-up of mould and mildew. It is best to place your deck where you can regulate the sun / shade it receives. This can be done with a pergola, cloth sun sail, deck umbrella, retractable awning, or moveable aluminium louvers. Permanent structures such as pergolas can be a handy place to attach lights, hanging baskets, speakers, mobile art, etc.
Privacy on one’s deck is often an issue. Ways to address this include a trellis, pizza oven, fireplace, water feature, pergola or gazebo with one or more walls, or fencing. Fencing can be softened with art, a trellis, or vines growing along wire mounted on the fence. Art can be serious or fun (for fun, have a look at kiwi artist Sarah C.’s durable outdoor designs: http://www.sarahcdesign.co.nz/outdoor-art.html).
If you do your homework, you can create an outdoor deck space that you, your family and friends will love!