Decking Oil and Stain Calculator

A coat of oil or stain will protect your deck, but before it can be applied you will need to strip the timber of tannins and oils to make sure any coating you put down will look smooth and even, not to mention last as long as possible. If the timber isn't stripped of its oils and tannins, the resultant oiling or staining may leave your deck looking discoloured or blotchy, especially on popular decking timber such as merbau, spotted gum and jarrah.

Common prep products include the following:

• Deck cleaner cleans and rejuvenates timber, shifting dirt, oils, grease and other contaminants off your deck and ensuring your coating holds fast to the timber.
• Some newer specialised timber prep products or oil and tannin removers, can let you skip the customary waiting period between cleaning and coating, helping you speed up your decking project.
• Timber primer is vital for areas that can expect more exposure to moisture, such as uncovered outdoor areas or bathrooms. Proper application of timber primer will leave your deck water-repellent, making cleaning easier, as well as more resistant to mould.
• If mould is already an issue, mould killer is applied after a deep clean to ensure it doesn't come back.

Water based products and oil based products differ in how they behave when applied to your deck. An oil-based decking product will penetrate into the pores of your timber, giving the deck a traditional, warm look. It will also leave a slight film on top of the timber, protecting your deck against water and UV rays. The trade-off for the traditional look is that it requires regular maintenance, often needing a re-coat every three months or so. An oil-based product can also get messy, with cleanup involving dangerous chemicals like turpentine.

Water-based decking oils don’t penetrate timber as deeply as oil-based products, instead leaving a far more resilient protective film on the surface of the timber, which lasts a lot longer than oil-based products. This protects against UV rays and water soaking in. They are highly durable with a low odour, and tend to dry much more quickly than oil products, making them far more easy and convenient to use than oil-based products.

Choosing to oil or stain your deck depends on the specific outcome you want, but it's important to remember that whichever you decide to go with, it should be done regularly. Coating your deck is not a once-off job; it will wear out over time, and will need to be repeated at least three to four times a year.

A general rule of thumb to follow is to remember that an oil will enhance the existing look of your timber, bring out its natural charm and feel. Conversely, staining your deck will change the appearance of your deck entirely, making a light coloured pine timber look like a darker Merbau for instance. It will also add a certain amount of UV protection to your deck.

Applying a new coat of oil or stain to your deck is never a good idea if rain is on the way. It’s worth putting off any work on your deck until you can safely assume the next two or three days will be sunny and dry.

If it does rain while a deck treatment is underway, the rainwater will seep into any wooden surface, swelling the timber and displacing any wet oil or stain. This can create discoloration in the finish of your deck, leaving ugly pale splotches in your timber instead of the smooth, even coat you expect. If it does rain during a treatment, sadly the process will need to be started again, starting with a complete hosing down of the deck again and a reapplication of the deck cleaner to clear away any dirt or debris brought onto your clean deck by the rain.

It's also just as important to avoid hot weather when treating your deck. Hot temperatures can lead to your product evaporating in the sun instead of penetrating the timber of your deck as it should.