Garden Decking Materials
Introduction
The vast majority of decks are constructed from timber, either softwood or hardwood, but the US market has also introduced a composite material.
Timber options
Timber is generally described as being either ‘softwood’ or ‘hardwood’. This does not refer to its relative hardness but to the type of tree it comes from; softwood is derived from evergreen coniferous species, while hardwood comes from broadleaved deciduous trees.
Not all timber is suitable for decking, so you should be sure to select timber that is fit for purpose. You should also check that your decking timber is derived from a sustainable forest source.
Softwood
Softwood is cheaper and easier to work with than hardwood, but does not have its inherent resistance to decay. To make softwood suitable for use in decking, therefore, it should be pressure-treated with preservative, also known as ‘tanalising’.
Those lengths of softwood that will be in close proximity to the ground or water should be pressure treated in accordance with Hazard Class 4. All other softwood timber not in contact with the ground need only be pressure-treated to the standards of Hazard Class 3.
Preservatives applied by a brush or through dipping will not provide long-term protection from decay and are therefore not suitable for decking.
- Cheapest variety of decking materials available
- Can be stained to the colour of your choice
- Provides a natural, variable texture and colour
- Requires an annual coat of water repellent to extend its life. Use one specific for timber decking, not just any repellent for an exterior vertical surface
- If not properly protected, may twist and warp as moisture enters or leaves the timber
- Not as dense as hardwood so shows dents from impacts and wear and tear
Hardwood
Most, but not all, hardwood is naturally more resistant to decay than softwood, so it does not require any pre- treatments. For decking, be sure to select hardwood that is classified as being naturally ‘very durable’ or ‘durable’ to ensure a long life.
- Requires little maintenance
- More dense than softwood so resists showing dents and abrasions from wear and tear
- Hardwoods are generally deeper, richer colours than softwood
- Can be stained to the colour of your choice
- More expensive than softwood
- More dense so harder to work with
Composite
Composite is quite an environmentally friendly product, being manufactured from a 50:50 mixture of reclaimed hardwood sawdust and recycled polyethylene plastic. This makes an excellent combination as the plastic protects the wood component from moisture and insect damage, while the wood conversely protects the plastic from UV damage, although colours will tend to fade to grey in time.
Composite therefore needs no sealants as it won’t twist, warp or rot and it’s splinter free. Just like timber, it can be sawn, drilled and routed using carbide blades. You should, however, still use timber joists to build the supporting frame as composite is not structural.
- Requires little or no maintenance
- Boards are flexible, especially when warm, so are suitable for finishing curved decks
- Not susceptible to insect damage
- Available in a range of colours
- Can be stained after 6 months to the colour of your choice
- Feels cooler underfoot than natural timber
- Not as easy to source in the UK as timber
- More expensive than timber - about twice the price of treated softwood
Decking Boards
Decking boards are usually supplied in widths from 75mm (3in) to 150mm (6in). Boards any wider than this are not recommended as they do not allow for fast enough drainage.
They should also have a chamfered or radius edge to aid drainage. Boards are also usually available in a range of surface textures; plain, grooved and ribbed:
If you choose grooved or ribbed decking, wherever possible you should lay these boards running perpendicular to any adjacent wall of your home to encourage water runoff in the right direction.
It’s also possible to source non-slip decking boards which have grit lines embedded in them.
Fixings
All fixings, including screws, nails, joist hangers and bolts, used outside must be very resistant to corrosion caused by moisture. If corrosion does set in, it can cause rust stains and the fixings can fail. You should therefore select fixings that are either made of stainless steel, or hot-dipped galvanised or coated to BS 7371 Part 6.
Two joist hangers will be required at each corner of the deck frame as well at either end of each internal joist.
It is possible to use nails to attached boards to the frame, but nails are susceptible to ‘popping’ as the timber naturally moves. Screws will not allow this to happen and can allow for individual boards to be removed for access.
Choose screw length to be twice as thick as the boards. Two screws should be used wherever each board crosses a joist. These should be positioned at least 25mm (1in) from the board edge in pre-drilled, countersunk holes. If using grooved boards, position screw holes at the lowest part of a groove.
Further information and useful links
- Find a Garden Decking supplier near you
- Find a Garden Centre near you
- Find a Garden Materials supplier near you
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