Decking Care

Decking Care

Garden decking has become very popular and can look great in many gardens but it can also become green, grimy, slippery and plain dirty and ugly after the winter months. The surface of timber decks becomes exposed to the elements such as sunlight, rain, snow and frost. This will inevitably lead to a deterioration of the colour if nothing else. However don’t despair you can get it back to the way it once was with some deck maintenance! There are 3 easy steps to get your decking looking good again and keeping it that it way. What you need to do is to is a three stage process; clean, restore and finally protect.

Before you start to clean the deck you should also review it to see if any damaged boards need to be replaced. Rotten or broken peices should be removed and replaced with new decking boards.

Discolouration is the obvious problem – all un-stained timber outside eventually turns a grey colour. Protective action can help to allay this problem, which is caused in the main by fine dirt particles entering the microscopic ‘pores’ of the timber.

The timber itself loses colour as ultra violet rays from the sun react with the timber. In this case, simply cleaning your deck will not restore the original colour. Though it will make it more attractive!

decking oil
decking oil

Discolouration of the deck timber has many causes – dependent upon the area in which you live – together with a number of biological causes.

  • Dirt by way of atmospheric dust particles, overhanging tree debris, bird droppings, BBQ debris!
  • Biological degradation of decks include, fungal activity, moulds, decay, and in shaded areas algae or moss.
  • Stains from unsuitable fittings can also cause problems such as un-galvanized nails, screws and bolts.
  • Problems that can be prevented are those often associated with placing planted containers and furniture on the deck. Planted containers – great deck assets – should have a moisture-proof stand underneath. An please do your planting and re-planting either off the deck, or with a good protective groundsheet under the work area.

Before treating any deck, the deck should be thoroughly cleaned. If in doubt, seek help from a professional decking company.

How to Clean a Deck
There are several preparations available fro DIY stores or Decking Specialists which to clean your deck. Go for the brand names, or reputable DIY stores own brand. Do not attempt to treat your deck or stain it without firstly cleaning it.

An alternative, is to use a weakened solution of TSP (trisodium phosphate) which can be obtained from any good paint shop. (It is used by pro painters to clean paintwork). Add a little household washing-up liquid to ensure a deep penetration. Try a small area first, and use as directed on the container.

Do not use any chlorine based bleach, for whilst this will clean your deck of algae and mildew in particular, it will also break down the lignin in the deck timber – which holds the wood together!

A weak solution of Citric Acid will help to ‘brighten up’ old greyed timbers. Most important – it is a non hazardous way of cleaning your deck. There are also some proprietary brands of wood bleach available, that will do the job.

Hydrogen Peroxide – which also has other lightening uses – will do wonders for lightening old timbers and in particular is good for the older darker deck timbers. It evaporates away, leaving no residues.

Most fungal growth can be treated with a general garden fungicide! If you use a combined Fungicide/Insecticide to clean your deck, then you can also kill of many ‘hidden’ insect pests lurking under the timber. This treatment does nothing to lighten the wood or to actually clean it of dirt – simply fungi/mildew and insects. It is not for cleaning the deck – simply to rid it of any infestation. Whether fungal infection will occur will depend on materials used in the decking construction (for more details on deck construction click here).

A jet washer can be used for cleaning decks BUT it must not be a heavy duty one. Something smaller than 1500 psi with a wide fan jet will be suitable for most deck cleaning jobs. Anything more powerful will leave the timber with a ‘wooly’ finish, as it will destroy the wood fibres. The result will be a deck that is very difficult – if not impossible – to clean or to treat.

Once the deck is clean – then and only then – you can think about a long term treatment regime to enhance the colour and longevity of your deck. Even after a suitable treatment application, regular cleaning of your deck is important to maintain the colour of the deck timbers.

Wood – like all living things – is made up of a honeycomb of minute (microscopic) cells. Whether softwood or hardwood, the cells are there – empty, waiting to be filled up with whatever is available! Deck boards are different in one main respect to other timber structures outside. Deck boards lay horizontal – not vertical like walled structures – so dirt and dust is not readily washed off. It simply lays on the deck until it finds a home. If it is larger than the cellular structure of the wood, then it will eventually wash off. If it is dust-like and smaller than the cell structure, then it will fill the available cell! This cell structure can be ‘capped’ by using Decking Oil.

The fact that your deck has been pressure treated in the manufacturing stage, does not mean that it requires no further treatment to alleviate stains and grey-coloured decks. Ordinary deck stain, simply colours the surface area of the timber. It does not fill up the cells, so dirt is still able to fill the spaces! A Deck Sealer is required to do the job – usually by way of a decking oil.

Decking oil is a special treatment/preserver that – whilst applied as a liquid – has a high potential ‘solids’ content, so that when it dries it solidifies thereby filling the pores/cells. Deck oil has high penetrating properties, so that it can enter and then solidify in the individual cells. Some deck stains simply coat the cells, still leaving room for the dirt to accumulate.

Penetrating oil finishes are much better for deck maintenance than polyurethane or varnish type finishes. Oils do not crack as the timber expands and contracts with the varying weather patterns. Deck oil treatments actually improve the structure of the timber, for once dry, the solids are stronger than the individual wood fibres that they bind together. Decking oils actually replace the natural oils and resins that get lost over time with deck timbers.

Decking oil should be applied after the deck has been thoroughly cleaned. We do not advocate the use of pressure sprayers, for if used indiscriminately a pressure jet can ruin the surface structure of the timber – leaving it with a ‘wooly’ feel – difficult to clean.


The oil should be applied in two coats using a soft-haired paint brush. The soft-haired option will allow for even spreading of the deck oil and also act as a sponge to mop up any surplus deck oil, which can then be used further along the board.

The oil should be applied thinly and well brushed out to ensure no puddles of surplus oil is left on the deck. This is particularly the case with grooved deck boards, as surplus oil can linger in the grooves, giving an unsightly appearance, and also taking a long time to dry.

With a thin application, the first coat will normally be touch dry in an hour in ideal weather conditions. A second coat is necessary to further protect the timber and also to enhance the colour if using a tinted oil.

If you decide to opt for a coloured oil – and it really does add impact to your deck – then always choose a lighter colour if you are uncertain. It is easy to ‘darken’ a lighter colour by oiling with the darker colour subsequently. It is virtually impossible to ‘lighten’ the colour after using a darker coloured oil.

A 5 litre can of oil normally covers around 50 sq metres of deck with 2 coats.

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