Get more from your slate investment.


Get more from your slate investment.

Decades lost

Insights from other disciplines help extend slate life

Roof slate lasts a long time. But its full and proper life is considerably longer than generally assumed. Delaying replacement for as many years as possible makes economic — and environmental — sense.

Inherently different

Roof slate is used differently than other building stones. It does not rely on mass for durability. Compared to blocks and slabs, slate, with a common thickness less than 9 mm (<3/8"), is in effect a veneer. Because it is overlapped and mortarless, capillary action plays a more significant role in aging processes. Because it is thin, it is distinguished by its surface area rather than its volume, rendering it especially vunerable to surface effects.

These conditions, and their chemical and mineralogical implications, could not fully be appreciated at the time that slatecraft evolved.

Also deserving

The stone facades of our monuments and important structures have been scrutinized. We understand what causes them to fail and proper remediation. Far less effort has been expended to apply these principles to slate roofs. There are some articles and reference materials that describe the aging of slate, but little has been done to use this information to slow aging processes.

No roof can last as long as the building it protects, provided it is a high-quality structure. But why view a slate roof as disposable, and its life fixed? Regardless of a particular slate's assumed lifespan — 50, 100, 150 years — the cost to replace it constitutes a significant investment. Why compare its longevity to other roofs, when in fact its life may be compared to that of the building?

Applying insights

Slate roofs can cost less, reserves can last longer, landfill burden can be reduced and energy to make and deliver replacement roofs can be saved.

Insights from archeology, chemistry, building conservation and mineralogy are applied to other parts of our buildings; it is appropriate to apply them to our slate roofs.

This site does so.

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