How to seal a timber deck

Monday, 2 March 2015 1:41:53 PM Australia/Sydney

Building a deck on your property is a great way to increase living space and add value to your home. But once you’ve built your masterpiece, how should you finish it? There are a variety of surface finishes to protect and enhance the timber while preserving its natural look. Let’s look at oiling your deck and getting the best results on different surfaces.

Project Steps:

  • Step 1: Preparing
  • Step 2: Sanding
  • Step 3: Cleaning
  • Step 4: Application



Decking oils come in a variety of colours. When choosing a colour, remember the shade may vary depending on the timber that you are using. Generally, the lighter the colour the more it is effected by the colour of your timber. More coats will add more colour. It's a good idea to let new decks weather for approximately 4-6 weeks to let the timber release its natural oils and tannins to bring out the beauty of the timber before sealing.

A good tip to test if the timber is ready for coating is to sprinkle a few drops of water onto the surface. If it beads, the timber will repel any new coating you are about to apply and you’ll need to do some more prep. If the water absorbs into the timber, then you are ready to apply the new finish.



Sanding is an important step in all surface preparation, particularly if it's a clear finish you are after. When sanding always go with the grain, as sanding across the grain will leave scratches. A previously painted deck will have to be stripped and sanded bare before recoating. But if you have used a penetrating oil or stain, you would usually recoat without much hassle.



Before you apply the finish, make sure the surface is clean, dry and free of any dust, dirt or oil. If you need to, wash down your deck with a deck cleaner and a deck scrub.



Check the days' temperature before you begin, if it's below 10C or above 30C then it's best to wait for another day as the drying time will be affected. Test your selected oil on a bit of decking off-cut to make sure it's the one you really want.

Many deck finishes can be applied with a brush, roller or spray unit, but oils are best applied by wiping liberally along the grain with a lambs wool deck applicator. Work along the whole length of 3-4 boards at a time, cutting in at the end of the boards as you go rather than applying it at the end of the finish all at once. Don't forget about your end grain as water can seep in and cause rot. Always work in the direction of the wood grain and use the natural breaks of the timber as boundaries for your sections.

Don't worry if you trap a few insects in the process of staining, wait until the finish dries, sand them away and touch up the area.

Now you can stand back and admire your handy work, that's all there is to it!

Copyright Mitre 10 Australia Pty Ltd. Reproduction prohibited other than for personal use. This guide has been produced to provide basic information and our experienced staff are available to answer any questions you may have. However, this information is provided for use on the understanding that Mitre 10 is not liable for any claim, cost, expense, loss or damage which is suffered or incurred (including but not limited to indirect or consequential loss), for any personal injury or damage to property suffered or sustained as a result of or arising out of or in any way connected with using the information contained in this guide. Mitre 10 advises you to call in a qualified trades person, such as an electrician or plumber, where expert services are required, and to independently assess any safety precautions that will need to be followed prior to using the information in this guide.