Installed properly slate roofs require relatively little maintenance and will last 60 to 125 years or longer depending on the type of slate employed roof configuration and the geographical location of the property.
Slate roof delamination.
However the geological makeup and orientation of the slate can over time be responsible for delamination.
At above right is a slate roof in poor condition on a poughkeepsie new york home.
This problem is known as delamination.
You can also check for gaps in the mortar joints along the ridge line.
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.
Worn slates at or near end of life in the upper roof above left.
Towards the end of its useful life these layers may begin to split apart in a process called delamination.
We see numerous broken slates slates with holes delamiated thin slates loose slates sliding down a few temporary repair slates.
The most common defect i encounter on slate roofs is inappropriate repairs.
Slate is a compact metamorphic rock geologically formed from fine grained sedimentary rocks of poor quality.
Delamination is caused by the reaction of certain minerals to long term moisture cycles.
When it is used as a headstone zones of residual internal stress can result in the partial detachment of vertical planes.
Some slates have been known to last over 200 years.
One example of this is chasing a leak with the black goop used by contractors unfamiliar with slate roofs.
This leads to a roof that is less sturdy and more prone to leaks and breakages.
Slate is a naturally occurring resource that forms in strong but distinct layers.
You can spot a sloped slate roof tile more easily from the ground.
If the tiles look to have a powdery surface this means the tile is deteriorating and you ll need to replace it.
Because slates are most likely to absorb moisture along their edges that s where delamination is often most obvious.
Such repairs are not only unsightly.
Other causes of slate roof deterioration include.
Delamination occurs when impurities contained within the slate primarily calcite and iron sulfides such as pyrite and marcasite react in association with hot cold and wet dry cycling to form calcium sulfate gypsum molecules that take up slightly more volume than the original minerals.
The delamination of poor quality slates where they split into layers mechanical damage like wind lift bad slating practice for example the use of thin nails that eventually cut through slates.
Over time these minerals expand causing layers to separate along cleavage planes.
Surface delamination on slates.
