CARING FOR PERGOLA TIMBERS
March 2022
Looking after your recycled timber pergola is vital in keeping it looking good for many years to come. We’ve put together important information, and tips & tricks to help you make the right decision for your timber.
If you’ve used high durability timbers like Ironbark or Tallowwood, then there is always the option to leave your timber to weather and go grey. These species don’t require the protection that oiling provides. Grey timbers will still need occasional cleaning with a wire brush on surfaces that are handled or sat on. This will remove any small splinters and roughness which may appear as the timber weathers. Brushing can be done with a cup style wire brush on a small angle grinder.
If you want to keep the original colour and appearance of the timber, then you will need to protect it with a coating. We recommend using an oil-based finish, preferably a natural plant based oil as they are renewable and carbon neutral. Natural oils are also a lot nicer to use, with less smell and fumes!
We don't recommend water based finishes for exterior timbers; in our experience they can trap moisture just under the finish which can cause accelerated deterioration of the timber.
Thor's Hammer supplies high quality, plant based Osmo oil finishes for interior and exterior timbers. There are two main options for exterior timbers that you can choose to use; the UV Protection Oil and the Decking Oil.
The UV Protection Oil is a clear finish which is recommended for vertical surfaces, so it is suitable for pergola posts. We generally find that the UV Protection Oil needs a recoat once every 6-18 months - this varies depending how exposed the timber is. For example, on the covered pergola at the entrance to Thor’s Hammer, we have recoated the north and west facing surfaces of the posts once in 3 years, and the other faces haven’t needed a coat yet. The fully exposed posts outside near our walkway have been coated once each year.
Osmo UV Protection Oil is a two coat system and should always be recoated before it starts to lose colour or deteriorate, as it loses all UV Protection as soon as the outside coat has been burnt off by the sun. There is no need to sand back the surface before recoating, as long as the previous coat is still in reasonable condition. If the surface has deteriorated too far, the Osmo exterior finishes develop a fine microflake which is very easy to knock off with a quick pass with sandpaper before coating.
The Osmo Decking Oil has a stain to it to give extra protection and will last longer than the UV Protection Oil - usually 18 to 36 months on vertical surfaces and around 12 months on horizontal surfaces in full sun. The stain in the Decking Oils will unify the appearance of the timbers and you will lose some of the natural variation in the colour, but you can choose a stain colour that matches the natural colour of the timber fairly closely. It is important to apply the Decking Oils (and all Osmo finishes) thinly as specified, otherwise you will stain the timbers too heavily, and also waste the product. The Osmo Floor Brush is ideal for applying the Decking oils thinly and quickly.
Do you have other tips & tricks that we’ve missed? Email us with your suggestions and we’ll include it in this blog post!
Written by Thor Diesendorf
Photography by Rohan Thomson