How to avoid common timber cladding detailing oversights?

 Monday, June 3, 2024

Detailing is a critical aspect of any construction project, and for timber cladding, meticulous attention to detail is essential. Regardless of the timber species and its durability class, improper detailing can result in various problems, from unsightly blemishes to structural issues like rot. Water is the primary concern, as its penetration can severely affect the timber’s performance and lifespan.

Proper detailing ensures water easily runs off the cladding and substructure, while allowing for natural ventilation to prevent excess water absorption.

In this blog, we will discuss about the detailing oversights in timber cladding. We have collected the expert advices from Architectural Liaison Technician Ross McCormack who have enlightened and provided practical solutions to avoid this critical thing.

Also, you would get to know how to ensure the longevity and integrity of your cladding installation. The blog will be much helpful for the woodworking professionals.

Guidance #1

Common oversight: Flat edges in cladding arrangement

Creating horizontal flat edges within the cladding arrangement or substructure can cause water to accumulate, keeping the area constantly wet and leading to rot.

This issue has traditionally arisen from the use of non-sloped horizontal battens and square-edged open rainscreen boards installed horizontally. Recently, there is a trend of using larger on-edge horizontal sections of cladding as breaks between floors or as casements at the top and bottom of cladding. To facilitate water runoff, it is essential to incorporate flashing with a drip point located at least 35mm from the front face of the horizontal section.

Guidance #2

Common oversight: Cladding proximity to ground

Placing cladding close to hard ground surfaces can present issues that can be avoided without significantly affecting your design. The main concern is impact water, which occurs when rainwater bounces off a hard surface, such as a patio, and hits the end grain of the cladding board. This is especially problematic with vertical arrangements, as the end grain is left exposed near the ground. The end grain, being the most absorbent part of the board (similar to the hole at the end of a straw), will weather much faster if subjected to constant wetting from impact water, leading to unsightly weathering patterns.

Guidance #3

Common oversight: Substructure ventilation behind cladding

Proper ventilation behind cladding boards is essential for maintaining optimal moisture levels and preventing rot.

The cladding substructure can absorb moisture from condensation, water ingress, and standing water. Without adequate ventilation, this moisture accumulates, raising the moisture content to unacceptable levels. Ensure the cladding substructure allows for unobstructed airflow, with a minimum ventilated cavity space of 20mm and clear gaps of 10mm at the base and top of the cladding. This requirement applies to both open and closed cladding arrangements.

Guidance #4

Common oversight: Interaction between timber cladding and metals

A little known fact about timber cladding is that it is a naturally acidic material, with the internal pH of most timbers sitting between 3 and 5. Timber species with a pH of 4 or lower are corrosive to metals, with some metals being more susceptible to corrosion than others. Corrosion occurs when rainwater comes into contact with the cladding, which then runs off and encounters metals below. One of the most used metals in construction today is zinc, however, this is one of the most susceptible metals to timber corrosion.

Guidance #5

Common oversight: Compliance with fire performance regulations

Fire performance and safety are paramount concerns in the modern construction industry. However, this blog aims to emphasize the importance of fire safety in designing buildings with timber cladding.

It is crucial to understand the required Euroclass rating for your project and to select appropriate materials and construction methods to ensure compliance and safety. Early consultation with relevant building standards authorities and fire safety experts is essential to ensure the cladding system meets regulatory requirements and enhances the building’s fire safety measures.

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