A great way to extend the living area into the garden is to build a timber deck. Like a veranda, it can be both a part of the house, and yet outside at the same time.  

Decks can be attached or free-standing. They are used for a variety of purposes, ranging from entertaining to places of seclusion and privacy.  Decks can be divided up or tiered to give different living areas.  Construction may be simple or complex, depending on your design, and according to the nature of the area where you wish to install your deck.

Foundations

All well-built construction jobs start below the ground.  Whether laying decking over existing concrete or paving, or building raised decking supported by upright posts, it is essential that the foundations are adequate to avoid subsidence.  Decking is heavy, particularly hardwood decking, and given that it is going to support human traffic, it is essential that it is not prone to collapse.  Most decks will require a building permit before installation.

In the case of supported decking, where the deck is attached to one side of the house or to another existing building, it is advisable to seek advice from a structural engineer before commencing work.  The same thing applies to the installation of decking on a roof terrace or balcony.  You will need advice as to whether the roof is sound and able to cope with the additional weight.

In all cases where a deck is raised and supported by vertical posts, the posts have to go into concrete foundations.  These foundations can be made from either pre-cast concrete piers or poured concrete footings.  To prevent rot, it is preferable if the timber posts go into galvanised steel ‘saddles’ that are then set in to the foundations.  

Support

Once the supporting vertical posts have been set into the foundations and the concrete has set, the beams can be attached.  Beams give the structure stability by linking the posts together.  

The beams in turn support the joists that provide further stability to the construction, and provide the base for the decking itself.  The decking is nailed at right angles to the joists.  With some more complex patterns it is laid at 45 degrees. 
Contact your local government building department to find out their requirements for the distance between supporting beams and joists.  

For very simple decks, it is not always necessary to use both beams and joists.  If it is close to the ground and does not have to support much weight, one set of supporting joists may be all that is required. 

In the case of decking laid over existing hard surfaces, there are two possibilities for fixing decks to the ground.  The decking can be laid on a sand or gravel base and then fixed to each other (technically speaking this is really paving with timber), or the supporting beams or joists are fixed to the brick or concrete supports using masonry anchors such as DynaBolt™.  This doesn’t have to be at ground level.  For example, a deck can be attached to the top of a garage with a concrete roof.  
As with any construction job, you should always avoid having timber come into contact with the soil.  The moisture and micro-organisms present in the soil will mean that even treated timbers will rot more quickly than if painted or stained and left in the open air.  

DECKING MATERIALS

Decking may be constructed of hardwood (e.g. Eucalyptus trees) or chemically treated timber (e.g. plantation pine). 
Hardwood timber is attractive and hard wearing, but may need regular painting to prevent rot (this varies in different climates).  Treated pine is rot-resistant, highly durable and relatively cheap, but prone to warping and buckling.
Most hardware suppliers sell decking timber that has been deeply grooved on one side.  When the decks are fixed with this side facing up, the timber becomes much less slippery to walk upon.  

Typically, decking timber is 75mm wide by 25mm deep.  However, it can be much wider and deeper.  If the deck is to be used for entertaining, then wide pieces of timber will make for a more attractive surface that is easier to walk on.  When decking over hard surfaces it is even possible to use railway sleepers. 
Note:  Some chemicals used to treat pine in the past have now been banned in some countries.

When nailing down the decking: 

  • A useful trick is to turn the nail upside down and lightly tap the wrong end of the nail on to where it is to go on the deck.  Because there is both a slight depression in the timber and a less sharp end on the nail, the wood is much less likely to split when the nail is driven home.   Most timber will buckle to some extent when left out in the elements, especially treated pine.  If you drive the nail in at an angle, this will reduce the problem of bowed and buckled timber.  
  • To avoid staining the timber - use stainless steel or hot-dipped galvanised nails.  
  • Nail free decking is another option, but may not be readily available in all places. 

Handrails and Balustrades

If the deck is to be raised above ground level, then handrails may be required.  The top rail is usually set at about the waist height of a typical adult.  (Most local government building departments will have regulations covering the height of railings.)  These rails are fixed to upright posts – either the supporting posts that are embedded into the footings, or posts that have been attached to the joists or beams.  
Pickets can then be attached to the rail and the joist or beam below.  Alternatively top and bottom rails can be attached between posts, and vertical balusters are fixed between them.  In either case, they will enhance the look of the deck and prevent children and other people falling off the deck causing injury. 
Many other options also exist including:

  • Metal strings between posts,
  • Stainless steel hand rails and supports, 
  • Glass in-fills, 
  • Café curtains for protection in some cases

Local government regulations may apply specifying what may or may not be used. This should be checked.