Corroded fastenings. Water damage. Weathertightness failure. These are all too common sights for disappointed homeowners whose cladding has interacted unexpectedly with incompatible nearby materials.
Don’t get caught out. Ensure your next cladding project keeps these common weatherboard materials safe from harm.
One of the most common installation problems with pine weatherboards is the interaction between the timber’s moisture content, the treatments it requires to remain weathertight, and the nails used to hold it in place.
Specifically, should steel nails be used in damp timber that has been treated with a copper-based wash, the nails will corrode far faster than normal. This could result in serious damage to the cladding.
Controlling this situation requires knowing not only how the primary material of the weatherboard interacts with other materials, but also how the fasteners and treatments interact as well.
You may be interested in: How different weatherboard cladding materials compare.
While cedar can escape the corrosion problem illustrated in the pine example above (due to the fact it doesn’t need to be treated to be fit-for-purpose), it has its own unique characteristics.
Namely, western red cedar (one of the most common cedars used for cladding) is acidic. This acid can leach out over time through rain contact and corrode unprotected aluminium/zinc-coated or galvanised steel objects in the run-off.
This is why many manufacturers stipulate the use of stainless steel or bronze fastenings for cedar. Failing to do so can result in galvanic corrosion and, ultimately, damage to the building.
Unfortunately, this installation mistake is easy to make—something as simple as failing to swap out the standard nails in a nail gun during installation can be enough. The only solution is vigilance, and frequent referral to the manufacturer’s instructions.
uPVC is known for its lack of chemical reactivity with most materials used in construction, making it safe to use in most projects regardless of material makeup.
Related reading: A basic timeline for building a new home
Fibre cement is, as you would image, relatively similar to cement in its material compatibility considerations. That is, there aren’t many materials that will react to it in a negative way once it has been painted with the 2 or 3 layers of latex paint it requires to remain weathertight.
This painting, however, can result in its own problems. Some sealants used in fibre-cement weatherboards can be unsuitable for painting and, should the wrong sealant be used, can fail unexpectedly.
One other point to note is that, while not exactly a “building material”, contact between fibre-cement weatherboards and soil/vegetation should be avoided.
Aluminium has a number of incompatibilities in construction, mostly centred around cement. Aluminium weatherboards should avoid contact with:
- Uncoated plaster cement
- Ceramic tiles with cement grout
- Clay bricks with cement mortar
- Unpainted, green concrete
As well as:
- Black steel
- Bright steel
Contractors should also aim to avoid allowing water runoff from aluminium to fall onto zinc or galvanised steel.
If in doubt, it’s generally a good idea to use steel fasteners when installing. These will have the lowest risk of corrosion in combination with the aluminium.
We hope this quick guide proves useful during your next installation. For more information about weatherboard materials, their advantages and disadvantages and their ultimate usefulness to your project, read our material overview below.