Tips for Fitting Cladding: Understanding Timber Movement

Tips for Fitting Cladding: Understanding Timber Movement

What Causes Timber Cladding to Move?

Timber is a natural product that expands and shrinks slightly with the environment around it. For this reason, timber can withstand far greater stresses and movement than rigid cladding materials. However, if not correctly installed, issues such as cupping, broken fixings and eventually water ingress, water damage and mould growth can occur.

That’s why when fitting timber cladding it is important to understand timber movement and plan for it.

What Will Help Reduce Movement in Timber Cladding?

Here are some points to take into consideration when fitting cladding to allow for timber movement.

• Specify the Right Timber

Make sure the timber is right for the project. Some timber species, such as Blackbutt, have a high durability class but also a high movement rate, meaning they can expand and contract more than other timbers. High-movement species require a good-quality oil coating to reduce the risk of moisture uptake. They also require an allowance for expansion between boards during installation. Alternatively, installing low-shrinkage timber such as Western Red Cedar will help reduce movement.

In addition to choosing a low-movement board, selecting cladding boards with a profile under 200mm wide can reduce movement. Wide timber cladding boards are at a higher risk of cupping and splitting. The wider the cladding the more potential for expansion or contraction.

• Timber Cladding Storage

While timber will initially expand and contract while it acclimatises to the environment, it should be kept dry and clean on site until it is installed. If not protected, water can absorb into the timber causing the cladding to expand. Water can also get trapped between boards during storage and cause damage. Heat from direct UV rays can also further dry the timber causing it to distort.

Store timber cladding undercover and at least 150mm off the ground to allow for ventilation.

• Moisture Control

The lack of adequate moisture control can contribute to timber movement. Yet with the correct installation of breathable wall wraps and a cavity batten, water that penetrates the cladding will be directed away from the structure. This barrier not only stops water from entering the wall cavity, it also allows vapour to flow freely out of the home without condensation affecting the cladding. If the vapour gets trapped, the cladding may cup as the outside surface dries.

• Use an Appropriate Coating

Select a high-quality timber oil or stain that suits the timber species and the environment. This will protect it from the elements and provide a longer-lasting timber cladding. If the timber cladding is not maintained and the protective coating is damaged, water can penetrate the timber and cause cupping, splitting and rotting. Unprotected cladding will be affected by weather and grey off.

It is advised to pre-coat timber cladding before installation to ensure it has 360-degree protection.

If you plan to paint your timber cladding, make sure you pre-paint one coat before installing it. This is to allow for timber shrinkage. If you don’t pre-paint and the board moves, you will see the line of the paint end along newly expose raw timber. This is more prevalent with dark colour that absorb heat causing timber shrinkage.

• Make Sure the Cladding is Fitted Correctly

Using the right fasteners for the job will not only make installation easier, it will ensure that the cladding is firmly fixed and fasteners don’t pull out once installed. Furthermore, selecting the correct finish for the environment you’re building in is crucial for the cladding’s longevity. For instance, using a galvanised finish in exposed areas or a stainless steel finish in areas close to the beach, will ensure the fasteners will not rust and allow moisture to enter the cladding.

Never tightly fit tongue and groove cladding profiles, there must be a small gap between boards to allow for any expansion.

• Choosing Timber Cladding

Bowens supplies a wide selection of top-quality timber cladding, so you have more choice when it comes to your next cladding project. Explore our timber cladding range online or visit one of our conveniently located stores across Melbourne and regional Victoria.