Guide written by:
Crystal, Owner of a small gardening business, Oxford
Decking can add a lot of decorative interest to a garden. But before you make your choice, you should be aware of all the possibilities – and limitations – of a timber deck. The following four main criteria should help you make the right decision:
Type of timber: First of all, you'll need to decide if you want a European or exotic wood, or composite. European timber will have to be weather-treated while exotic woods are naturally more durable – but also more costly! Composite, on the other hand, is made of recycled wood particles mixed with resin. It's important to check the timber grading in terms of strength and durability, and to ensure the wood is treated and FSC-certified.
Decking format: you'll have to choose between decking boards and tiles which all come in different colours, sizes and finishes.
Installation: this all depends on the type of timber you choose (i.e. solid or composite, boards or tiles), your garden layout and your own desires.
Maintenance: less complicated than you might think, deck care usually consists in a quick sweep for composite decking or a lick of penetrating oil for solid wood decks.
In terms of decking material, you will have to choose between European and exotic woods or composite.
In terms of European timber, softwoods like Scots pine, maritime pine and Norway spruce are popular options as they are light-coloured and reasonably priced. However, as these woods are sensitive to the elements, they must be treated.
This might be an autoclave wood treatment which will help the wood to deal with the elements as well as wood-boring insects and fungi. In this case, the wood is treated by a process of timber impregnation. Alternatively, the timber may undergo a High Temperature Treatment (HTT) which involves heating the wood to over 200 degrees. This process will alter the colour of the wood slightly.
European hardwoods are more hard-wearing than softwoods. Oak, chestnut and black locust are all naturally durable but they can be expensive. Furthermore, tannins held in the wood can rise to the surface unless the deck is treated on a regular basis.
Exotic woods are naturally rot-proof and come in a range of dark tones. However, this makes them more expensive and you will still have to treat the wood to stop it from fading.
Once more, you can choose from a wide range of species including:
teak, the colour of which ranges from brown to yellow;
ipe, orange in tone;
yellow balau, shades of brown;
merbau, red tones;
itauba, brown tones;
massaranduba, orange/red in tone;
eucalyptus, yellow, pinkish or white;
As exotic timber is not treated, it will need to be coated with a penetrating wood oil.
Composite is made up of recycled wood particles combined with a plastic resin. It comes in a wide range of colours and is designed to closely resemble natural wood. However, it is rot-proof and UV- and frost-resistant. What's more, it won't warp, splinter or show any obvious signs of age. Composite is also less expensive than exotic woods and is very easy to care for. All the same, while composite is made to look like wood, it's no replacement for the real thing! What's more, it conducts heat meaning your deck will warm up in the sun.
To ensure your timber decking is environmentally friendly, there are two main certifications to consider.
PEFC certified wood has been sourced from sustainably managed forests grown using environmentally friendly methods. The organisation also sets standards on health, labour and safety issues. Forest owners must demonstrate responsible practices involving forest regeneration and flora and fauna. Wood is monitored from the tree through to timber processing and manufacturing.
FSC certification also guarantees that the decking timber you buy comes from a sustainably managed forest. However, it puts less of an emphasis on the timber supply chain than PEFC and standards have to be interpreted at the local level. It is also less common than PEFC.
Timber is graded according to strength and durability which gives you an idea of how well the wood will cope with the elements. A minimum timber strength class of C16 is required for decking but higher classes of C18 and C24 will give structural elements greater strength to cope with higher loads. Timber decking is also categorised by service life with 15, 30 and 60 years being the most common options. The British standard BS EN 350-1 sets out five different classes for resistance to wood-destroying fungi.
Timber durability classes
When designing your decking, you'll have the choice between decking boards and tiles. Each option comes with its own set of features to think about.
A popular option for smaller decks, decking tiles and are usually square. They come in a range of dimensions the most common of which are:
40 x 40 cm;
50 x 50 cm;
100 x 100 cm.
With this option you can mix up the direction of the boards, patterns and materials to create a completely unique deck.
Decking boards come in a variety of lengths to fit any space. While usually they usually range from about 210 to 240 mm in length, some boards can measure up to 400 mm. It's up to you to pick the right size depending on the size of your decking area in order to minimise on the amount of cuts and joints you'll have to make later on. The width of decking boards is usually between 90 to 200 mm and they can be from 21 to 28 mm thick.
With this option, you can choose exactly how you want your decking boards to be installed: lengthways, widthways, diagonally, in a chevron design and so on.
Decking boards and tiles come in all sorts of colours and tones depending on the species and age of the wood. Exotic wood, in particular, tends to fade over time. In terms of finish, both boards and tiles can be smooth or ribbed. Some boards may be smooth on one side and grooved on the other
so you can choose which side to use or alternate both. It's worth noting that while ribbed boards are usually thought of as non-slip, the reverse is usually true. In fact, the grooves tend to cling onto water which causes a sort of aquaplaning effect and can lead to moss growth (which is slippery in itself). Regular cleaning is therefore required to prevent this from happening.
Composite decking boards are a more cost-friendly alternative to solid wood. Hollow decking boards offer significant benefits such as easy care and durability but will require special clips to install. These mounting clips are usually individual to the manufacturer and the specific model.
Composite is made up of the following components:
wood fibre (sawdust, wood flour);
polymer resin (polyethylene, polypropylene or PVC);
pigments (dictates the colour of the material);
additive (fungicide, hardening agents, etc.);
Composite decking boards present a number of benefits:
they are less expensive than boards formed from exotic wood;
they are non-slip even when wet;
they look like wood but don't feature any knots;
they come in a wide range of colours including brown, grey, sand, and so on ;
they are rot-proof;
they don't require a great deal of care beyond basic cleaning with a brush and mild detergent;
they boast a long service life of up to 30 years (depending on model).
Composite retains and distributes heat more readily than other materials.
In order to select high-quality composite boards, you'll have to be vigilant. Here are the factors to look out for:
Wood to plastic ratio: go for a lower wood content as if the higher the wood content, the higher the moisture content which can lead to warping and swelling.
Density: the higher the better.
Finish: the surface should not appear mottled.
A long warranty.
A lower expansion and contraction rate is preferable but this kind of information is rarely supplied by the manufacturer.
Hollow composite decking boards are less expensive than solid boards but they are more fragile. If you cut these boards, the hollow profile will be visible and you won't be able to screw through the boards to fix them at the risk of weakening or even breaking the board. For these reasons, hollow composite boards often make up low-end composite decking.
Solid composite decking boards look more like wood as they feature a solid profile all the way through the board (which will be seen if the board is cut). They are more shock-resistant and durable, but more costly than hollow composite boards. You can, however, screw through any part of the board during installation. Solid composite decking is considered the high-end option thanks to these qualities.
Semi-hollow composite decking boards are just about as hard-wearing as solid boards but are about 25% cheaper. That said, the profile of these boards is not terribly attractive and their service life lands somewhere between solid and hollow boards. However, these boards will cope with screws.
Wood fibre content tends to be fairly similar no matter whether you go for hollow or solid composite.
Composite decking is naturally non-slip but smooth decking boards will be more so than ribbed ones. Smooth decking boards are also easier to clean as there are no grooves for dirt to build up in. If you are screwing through the boards themselves, smooth decking will provide a better finish as the screw heads can be covered with a wood putty in the same colour as the decking boards.
When it comes to choosing between smooth or ribbed decking boards, it's mainly a matter of taste.
Composite decking boards come in all sorts of sizes:
they can even stretch up to 4 metres in length;
and 300 mm in width.
Composite decking is incredibly easy to care for: you just need to brush it down regularly with a bit of soapy water. A pressure washer can be used for spring cleaning but only using a great deal of caution.
Exotic wood decking can be cleaned using a mild detergent and brush. You'll also need to apply a special penetration oil once or twice a year to stop the wood from fading.
Some oils are tinted to revive the depth and colour of the wood. If the wood has already started to grey, you can use a wood cleaner. In terms of pressure cleaning, it is possible but you will have to apply a lot of caution.
A penetrating oil is basically a special type of oil designed to saturate wood. These products are not film-forming but rather provide nourishment deep into the wood. Penetrating oils dry very quickly and you can choose from many different shades. Despite their advantages, penetrating oils are generally less environmentally friendly than other outdoor oils or stains. It's worth comparing the labels on each product.
European woods can also be cleaned using a mild detergent. If your timber decking boards or tiles haven't been autoclave- or HTT-treated, the wood must be varnished or stained. Varnish is film-forming and not always microporous while stains are always microporous and usually contain a fungicide. Both of these coatings provide protection against UV rays and will stand up to fairly extreme weather conditions. But if you're stuck between the two options, go for a stain. Wood stains will improve the weather resistance even of treated timber.
Decking tiles can simply be clipped together over any hard surface or set on top of PVC or concrete decking supports designed specifically for this purpose. The bonus of using decking supports, or riser pedestals, is that you will be able to deal with any levelling issues.
Timber boards can be screwed into or clipped onto wooden joists at right angles. The joists themselves can be set up over concrete blocks or even on top of decking supports. The thicker the boards, the wider the joists can be.
Of course, all wood expands and contracts over time and this can have consequences for your decking. Allowing your wood to properly acclimate in your garden before installation can prevent issues such as warping or splitting down the line. Of course, choosing a high-quality timber that has been treated properly should also help you to avoid these types of problems.
Guide written by:
Crystal, Owner of a small gardening business, Oxford
From a background in waste transportation, I became a farmer specialising in organic gardening. A graduate of Horticultural Production, I tried for several years as a young farmer to settle in the beautiful region of Oxfordshire. After many disappointments, I finally started a small-business in home services, specifically in gardening, assisted by my loving, dear husband. Passionate about nature and wild edible plants, I am very attentive to ecological solutions and respectful of our environment in all aspects of my daily life. From the vegetable garden to the flower beds, from seed to harvest, I have all kinds of advice up my sleeve. Do not hesitate to ask me your questions.