Looking After Pressure Treated Fencing

Timber fencing is a natural product that reacts to its environment. Wet, dry, hot, humid, sunny, overcast or cold. All types of weather affect timber. Changing weather patterns is what causes fencing timber to warp, twist, shrink, expand or develop shakes (splits in the wood). All of these problems are actually caused by moisture movement into or out of the timber.
Replacing or repairing fencing is necessary as it forms the border of your property, keeping children and pets in and others out. It is also the first thing people see when they visit your home. So, it makes sense to look after your new fencing to keep it looking good and extend its life.

You cannot stop wood from being wood. Therefore, any wooden fencing will have some of the issues mentioned above to a lesser or greater degree. ( see our information sheet on the Characteristics of Timber) However, we can minimise the risk of having severe problems, and how you prepare and maintain your fencing will help.

Over the last decade, the maintenance and decorative treatment options for wooden fencing have changed. Many of the more traditional treatments, like Creosote, have been banned or their use restricted for health and safety or environmental reasons.
We have amended our fence care information and recommendations accordingly.

Options

The main treatment types currently available are:
1. Water-based decorative coloured timber coatings. These generally contain water repellent and are fungal/algae resistant. It is best to avoid darker shades which can attract heat from the sun and make fencing timbers more likely to warp, twist, split or shrink.
2. Oil or chemical-based decorative coloured timber coatings. This option is split into timber surface protective treatments and timber preservers. Again, as mentioned above, try to avoid darker shades.

Protective treatments

These are generally coloured and have a water repellent. These provide surface protection for the timber, usually with some biocidal effects.

Timber preservatives
These can be clear or coloured and may have a water repellent feature. Preservatives usually penetrate much deeper into the wood. Wood preservatives contain more potent anti-fungal, algae and wood boring insect protection than the protective treatments.

Clear water repellent

If applied correctly, it should have minimal effect on the colour of the timber. Although these repellents have no biocidal impact, they help reduce moisture content changes of the wood, with a subsequent reduction in the chances of severe timber movement.

Exterior Wood oils, including decking oils

These can be clear or tinted to stain the timber. The oil selected should be UV stable to keep the wood looking good for longer. Again, we recommend using a clear or light-coloured oil. As before, try to avoid darker shades.

Paint

We do not recommend using any form of paint to protect wooden fencing.

Do nothing!

Your fencing is pressure treated against rot and insect attack, so you can leave it as it is. The timber fencing will slowly change to a silver-grey colour and retain that colour permanently. However, the fencing will be more susceptible to the vagaries of the weather and more susceptible to natural timber movements.

Whatever treatment you choose, please read the container’s label carefully to determine what it contains, what it should do and any warnings/usage instructions before purchasing. Also, check it is suitable for your timber finish – sawn or planed. Not all treatments are ideal for both types.

Recommendations

Allow the pressure treatment in the timber to dry out naturally, then add two coats of good clear UV oil that can alleviate the movement of moisture in both directions, repelling rain and sealing the tiny holes in the surface of the timber that lets water out. It will also help your fencing to retain its colour for longer. Pay particular attention to all end grain.
We have found a clear or lightly tinted oil such as Light Oak to give the best results. Darker tints are available, but because they absorb extra heat from the sun, they can cause problems.
Retreating with a top-up coat every spring or even every couple of years will go a long way toward keeping your fencing looking good throughout its life.

OR

Allow the pressure treatment in the timber to dry out naturally, then treat initially with a clear timber preservative to maximise protection paying particular to the end grain. 
Retreat with a clear water repellent or light coloured protective treatment containing a water repellent, preferably annually.

OR

Just treating annually with a good quality clear water repellent will help. Making sure to give the upper surfaces and end-grain like the tops of posts, feather edge board tops and panel capping a good coating.