Synthetic Shake

A synthetic shake is a manufactured roofing unit moulded to reproduce the look of split wood shakes. Most are made from the same families of materials as synthetic slate: engineered plastics such as polypropylene or polyethylene, or rubber compounds, combined with mineral fillers, pigments and UV stabilisers.

Why they are used

• No rot or insect attack: plastic and rubber shakes do not decay, split along the grain or host fungi the way cedar can. Rubber shakes made largely from recycled tyres are described as resistant to rot, curling and cracking and as non-absorbent.
• Fire: wood shakes are combustible and restricted in some fire-prone areas; fire ratings of synthetic shakes vary by product and assembly.
• Hail: many products carry UL 2218 Class 4 impact ratings.
• Weight: similar to synthetic slate, roughly 200-350 lb per square (10-17 kg/m²).
• Uniform supply: colours and sizes are consistent, while natural cedar quality varies.

Limitations

• Synthetic shakes lack the natural variation and silver-grey weathering of real cedar, though many are made in blended colours to imitate it.
• Thermal expansion is greater than wood, so manufacturers' spacing rules must be followed.
• Long-term performance of many products is still being established; fading and heat distortion are known concerns for some plastics.

Installation

Synthetic shakes are typically nailed to a solid deck with corrosion-resistant nails. Requirements for underlayment and interlay differ from those for real shakes and vary between manufacturers.

Comparison with wood

Real cedar shakes are split along the grain and weather naturally to silver-grey, while synthetic shakes keep a more constant colour. Choosing between them usually comes down to local fire rules, hail exposure, maintenance expectations and appearance.