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All About Timber Decking

Skill Level: Intermediate


A deck may be thought of as an open air extension of your living space. It may be built against an outside wall providing a patio area, or it can be free-standing and located in some other area of the garden, providing a place for entertaining, perhaps a barbeque, or play area. Your deck may surround a water feature or a nearby tree; you may wish to construct a bench around the tree.   The options are almost endless, and are restricting by only the imagination. Decks are also functional and can be the solution to various garden problems; to improve upon sloping and rough ground, or enhance a shaded area where little will grow. Decking can be a cheaper alternative to expensive landscaping costs
You don’t need to be a carpenter to build a deck. Only basic skills are needed, the right tools, and careful preparation and planning.

Design and Planning

Start by drawing a simple plan of your home and garden, and sketch in where you want the deck located and the design of the deck. From this you can calculate the approximate quantity of materials and deck boards you will require for the job.


Decking can be constructed from either hardwood or softwood, and each will give years of pleasure and service with a little, regular maintenance. Softwood decking is cheaper than hardwood decking and some basic difference are;
  • All decking expands and contracts during weathering. But hardwood less so than softwood.
  • Hardwood timber contains its own natural preservative oil and so requires somewhat less maintenance.
  • Hardwood decking is more expensive than softwood decking.
  • Hardwood decking may have higher longevity.
  • Softwood decking will readily accept preservatives and coatings.
Decking boards in addition to coming in a variety of timbers and colours may also have differing surface profiles. They are grooved, reeded and smooth. Grooved and reeded deck boards do not provide additional slippage qualities. Grooves become dirty and encourage algae growth and requires frequent cleaning. Smooth surfaced deck boards are the profile preferred by many people including designers and architects for the clean lines and aesthetic appearance. Smooth faced boards may be treated with an anti slipping agent for added safety.
Always treat cut ends of decking with a preservative to ensure that the timber remains structurally sound for as long as possible.

Deck frame Structure

The key to constructing a good decking area is the frame, the foundation of the structure. If the decking is being built on an existing patio, with the frame support beams near or on the ground, then H4 grade sawn treated timber 50mmx150mm should be used for the main support beams. The frame is constructed in a similar way to a floor frame, starting with the outside perimeter, and then infilling with subsequent joists at approximately 400mm centres. Cross member support beams are added to give additional strength and stability.
Before building the frame you will need to decide which way the decking boards are to run then build the main support beams in the opposite direction. Where the decked area is attached to an outside wall then a support beam known as a stringer [100mmx50mm, H3 or H4 timber] is bolted along the length of the wall at the desired height, to which the main support beams may be attached, enabling secure fixing of the frame to the building and the fixing of deck board ends. If the decking is to be raised above patio/ground level then this can be achieved by supporting on a building brick or other forms of padding to obtain the desired height. The more support that is given the less bounce the decking will have. Where decking is to be fitted to a support frame attached to an outside wall then level the frame to achieve a slight fall away from the building to allow water drainage.
Where decking is to be constructed as a free standing area in the garden then securing of the deck support frame may be achieved by concreting wooden support posts into the ground at a minimum of 30cm depth. The posts should be approximately 100mx100m and should be H5 treated timber. These should be spaced at every second support beam (joist).
The fixing of both the deck frame and deck boards should ideally be carried out using screws. Stainless steel screws are usually used for hardwood decking and zinc plated screws for softwood.
It is important when fixing deck support frames to check and recheck levels throughout the construction and installation process. Adjustments may be made to levels using wedges.

Fixing the Deck Boards

With the frame constructed and secured, the ground should be covered with a weed growth inhibiting fabric.
The first step to be carried out is to lay all the decking boards on the frame so that you can work out where the joints will be and the most economic way of using the deck lengths. As the decking board lengths supplied will all be the same length, we need to consider whether we wish to stagger the joints as in brickwork for example or have the joints in the same position for each board, giving the appearance of a grooved line running transverse to the boards.
The final stage is to secure the decking boards to the frame. This is best carried out by screwing the boards down so they can easily be removed at a later time for either repair or replacement or for access to manhole covers. When screwing the boards down it is best to pre drill the board holes and countersink, having established and marked out the drill lines across the joists.  The boards should be arranged so that the end of the board is fixed at the mid width point of the joist. The deck boards should be spaced, for expansion reasons, approximately 3-5mm apart. This can be best achieved by using a spacer bar.

Deck Fittings

All decking that is raised and stands more than 1m above ground level must have a handrail. Where handrails are required they must be at least 1m in height from the deck. Any vertical slats cannot have a gap exceeding 100mm and there must not be anything horizontal that would form a ladder effect.
There is a variety of handrails and trellises available specifically designed to enhance the aesthetic appearance of decked constructions. When considering the construction of additional decking features and their construction and fitting, careful thought and planning is required.


Tools you will need:

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