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How to stain and protect decking timber

Adam_W
Valued Contributor

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Staining or oiling decking timber and regularly maintaining your deck will keep it looking fantastic for years to come.

 

This guide shows you how to select and apply treatments to protect your deck and extend its lifespan.

 

What is the difference between decking oil and stain?

 

Stained deck by maknilsinStained deck by maknilsin

Both decking oil and stains are semi-transparent, which allows timber grain and some colour to show through. There will be variation and crossover between products so always read the details on the product itself. Here are the main differences between decking oils and stains.

 

Decking oil

 

Decking oils are designed to enhance natural colour. Most do not offer a lot of UV protection so a natural degree of colour change will happen with time. In most cases, decking will start to turn grey. Oils are better at penetrating and nourishing timber, and they tend to offer a higher level of water repellency and protection from moulds and rots.

 

Stains

 

Stains are designed to change timber colour. They offer a much higher level of UV protection but lower levels of timber protection unless oil based. Stains can work to enhance patterns of grain in the timber especially when rejuvenating old decks.

 

Oil-based stains will require clean-up with turps while water-based products can be cleaned up with water. Water-based oils offer the best of both products – oil-like penetration with the ease of water clean-up.

 

A major difference between oil and water-based stains is in their application – an oil will need to be left for six hours or more before it can be given a second coat whereas a water-based product can be recoated in as little as an hour.

 

Why stain or oil my deck?

 

Timber starts to age and breakdown when exposed to the elements and daily wear and tear. Timber dries out leading to shrinking, cracking and splitting, which then allows water and dirt to penetrate the timber and accelerate its breakdown.


You can leave a deck to naturally weather but this will lead to it changing colour and can shorten its lifespan. Stains and oils offer protection and nourishment that work to extend the lifespan of your timber. Stains are available in a range of colours, allowing you to change the tone of your decking. Love the look of Merbau but can’t justify the cost? You can stain treated Pine with a Merbau-tinted product for a similar look.

 

What tools are needed to stain or oil my deck?

 

The most common tool to stain or oil a deck is a lambswool applicator. These are on a long handle and look a little like a mop. The idea is that they absorb a generous amount of treatment and can then easily apply it over a wide area. There are also large-head brushes on long handles designed specifically for decking use.


Whatever type of treatment you use on your deck, many of the tools and techniques required to apply them are the same. A deep bucket-like tray is the best option for holding treatment as you apply. This is because oils and stains have a much thinner consistency than wall or ceiling paints and will slosh and splash out of a typical roller tray due to its shallower sides.

 

You may also need a couple of different sized brushes for any edges up against walls, timber ends or spots the long applicator can’t reach.

 

Can I use a pressure cleaner to clean or renovate my deck?

 

Merbau front porch deck by kelliMerbau front porch deck by kelli

Pressure cleaners can be a fantastic way to deep clean a range of surfaces, but they are considered an aggressive way of cleaning. They also tend to leave porous materials like decking timber with a lot of moisture.

 

When rejuvenating a deck, a pressure cleaner is ideal for getting embedded material out of the cracks especially on top of bearers or joists. After pressure washing, give timber adequate time to dry before treatment.

 

Most hardwood decking boards can tolerate pressure cleaning. Use care and test in a small area first to get your pressure level right. Too much pressure can open cracks, leave marks and make timber go “furry” as it damages grain.

 

As treated Pine is a softwood it can be easily damaged by overly vigorous pressure cleaning. Keep pressure lower and the spray head further away from the deck surface.

 

How soon can I seal a new deck?

 

We recommend letting a deck naturally age from one to three months before treatment. Let’s look at the reasons for this.

 

Moisture

 

Decking boards will accept treatments (especially oil-based ones) more effectively if the timber is dry. Moisture will repel oil-based products and dilute water-based ones, preventing quality penetration and causing patchiness in the finish.

 

When timber is dry, the grain tends to open a little making penetration easier. What takes place is a capillary-like action with the dry timber sucking the product in. If in doubt, check the recommendations on your product label.

 

Tannins and oils

 

Tannins are a natural chemical component of hardwood timber such as Merbau or Spotted Gum. Tannins are water soluble and will “bleed” every time they are wetted down. If left to happen naturally, this process can take months.

 

Tannins need to be removed before oiling or staining or they will interfere with treatment performance, penetration and colour. Tannins and oils do age out of timber reasonably quickly but the time will vary with local conditions.

 

You can reduce some of this delay by regularly washing down the deck using a suitable timber preparation product that is designed to remove tannins and oils. You will still need to allow the timber to dry. Talk with a paint specialist for advice on the best products to use if you do need to accelerate the curing process and treat your new deck sooner.

 

Should I seal treated Pine cut ends?

 

Treated Pine is pressure treated with a mix of chemicals to prevent attack from insects and decay that causes fungus. With larger timber such as sleepers or posts, this pressure treatment may not fully penetrate to the core of the timber and exposed cuts can be prone to rot or insect damage.

 

Due to their thinner nature, this lack of penetration is not generally an issue with treated Pine decking boards, but it is considered good practice to seal cut ends. Use a paint brush to give any exposed ends or cuts at least two coats of your selected treatment. The end-grain usually takes it in very quickly and requires extra coats.

 

How often do I need to re-treat my deck?

 

Hardwood deck by DIYgalsHardwood deck by DIYgals

Most manufacturers of decking oils and stains recommend re-coating your deck every 6–12 months, but this can vary due to different variables such as:

 

  • Different oils and stains have varied lifespans. Traditional oil tends to last longer as it is more of a penetrative treatment than a surface coat.

 

  • Due to the nature of the timber, receptiveness of the grain to the treatment will vary based on timber type.

 

  • A deck in a spot highly exposed to the sun or beside a pool where it may be exposed to frequent splashing and pool chemicals will need treatment sooner than one in a sheltered spot.

 

  • A small, sheltered deck off a bedroom with occasional use may only need resealing every couple of years. Your main entertaining deck will likely need re-treatment at least every year.

 

There is one sure-fire way to know when it’s time for a reseal – how does it look? When your deck is looking tired and there are obvious signs of wear, then it’s time to break out the cleaning and deck-oiling gear.

 

Look for these signs to determine if a full restoration is needed:

 

  • If previously coated with a product such as a water-based oil you may see spots starting to peel off or wear thin, particularly in high-traffic areas or where exposed.

 

  • If a traditional oil has been used, the surface will look dry and the timber will be distinctly discolouring – going silver or grey.

 

  • Nail heads may have risen.

 

  • Cracks may be visible in the grain and the timber may be slightly splintering.

 

See How to renovate a timber deck for a step-by-step guide to repairing and rejuvenating your deck.

 

How do I maximise oil or tint lifespan?

 

Regular maintenance can dramatically extend the life of your deck treatment.

 

  • Use deck covers under barbecues and food service areas to catch any oil splatters and dropped food. Lift covers and clean underneath frequently or roll-up and put away when not needed.

 

  • Clean up spills as soon as practical.

 

  • Avoid using any solvents or harsh chemicals on your deck.

 

Decking boardwalk by Adam_WDecking boardwalk by Adam_W

  • Don’t let leaves and dirt accumulate as this can stain or potentially damage your deck treatment. A rechargeable leaf blower is the simplest way to keep it tidy. After wet weather or during cool damp times make sure your deck is kept clean.

 

  • Give your deck a gentle wash or mop down with mild detergent at the start or end of every season.

 

  • Don’t use harsh cleaning methods, such as pressure cleaners, on decking unless you are about to rejuvenate and reseal your deck.

 

 

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