Diagnosis guide · Guide 77 of 101

Slate delamination, flaking and surface spalling

Slate splits naturally along cleavage, but uncontrolled separation in service can indicate unsuitable material, weathering or localized damage.

01

Document severity and distribution

Record whether flaking is thin and superficial or whether whole layers and corners are separating. Compare exposed and sheltered slopes and note moisture, freeze-thaw and runoff patterns.

02

Test representative areas carefully

An experienced slater can inspect sound, edges and cleavage without destroying good roofing. Avoid aggressive tapping or walking that creates new damage.

03

Separate isolated pieces from systemic failure

A few damaged units can be replaced. Widespread progressive delamination across the same product may require sampling, testing and a long-term replacement strategy.

Further technical reading

Recognized sources behind this guide

Slate Boss writing is original. These links provide additional standards, preservation guidance and industry reference material.

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