Slate Roof Delamination

Slate is a naturally occurring resource that forms in strong but distinct layers.

Slate roof delamination.

Textural slate roofs are perhaps most often associated with tudor style buildings where slates of different colors are used to enhance the effect. This leads to a roof that is less sturdy and more prone to leaks and breakages. Terne coated sheet iron lead coated copper lead sheet galvanized steel and copper are the most common flashing materials used with historic slate roofs. Slate is a compact metamorphic rock geologically formed from fine grained sedimentary rocks of poor quality.

Towards the end of its useful life these layers may begin to split apart in a process called delamination. Surface delamination on slates. Evaluation of these components does not differ from any other roofing system. We see numerous broken slates slates with holes delamiated thin slates loose slates sliding down a few temporary repair slates.

At above right is a slate roof in poor condition on a poughkeepsie new york home. For slate roofs flashing is often the weak link. Notice the surface delamination on some of these slates. Delaminating roofing slate if the delamination is only in the upper surface layer of the slate the material may have substantial remaining life.

Depending on the quality of the slate many look new despite more than 200 years of exposure. Also ask how many of the roof slates are delaminating at all note the neighboring slates on this roof are sound. This is not a normal thing to see in slate tiles unless there is water leaking underneath the slate and pooling. But slate roofs commonly outlast the flashings.

Powdering on the underside of the slate this is known as efflorescence and is composed of dissolved salts after water evaporates. Tiles that exhibit delamination must be replaced. However the geological makeup and orientation of the slate can over time be responsible for delamination.