When to Replace Your Slate Roof
Failing Slate
Slates fall apart when moisture is wicked into the slate and the the minerals trapped inside the rock expand or dissolve. Slate is the aftermath of microcrystalline shale fragments and clay from the ocean floor hardened by millions of years of pressure and heat. During this process mineral deposits get trapped into the rock. Now that you have context, here are the three signs that your roof is falling apart:
Mineral Deposit Breakage
Slates are mainly comprised of quartz, mica, and chlorites.
Sometimes, mineral deposit impurities, iron sulphide and carbonates, are trapped within slate and become a weak point within a slate.
As minerals within these deposits begin to dissolve the slate can become water logged or break apart on the mineral deposit line.
2. Moisture Wicking
Believe it or not, slate is a porous rock and absorbs water. As the minerals in the slate begin to dissolve moisture will will get trapped in the slate causing it to become brittle and soggy.
One tell-tale sign that moisture is trapped into the slate is efflorescence, a white powdery lime residue left on the surface of the slate when water evaporates. While this does not mean the slate is ruined, it’s a sign that the roof is deteriorating.
3. Delamination
Slate is split into thin slices called cleavage planes. The moisture within the rock freezes and thaws throughout the year slowly working its way from the edges of the slate towards the center. This freeze-thaw cycle slowly cleaves the slate apart causing it to flake. This separation of of cleavage planes is called delamination.