When this can be detected in a number of slates across a roof it is termed nail sickness.
Problems with chinese slate roof tiles.
Nowadays around 75 of global production originates from spain so it is hardly surprising that spanish slates present a tempting alternative to those building their own home.
Although slate quarrying was not common in the united states until the latter half of the nineteenth century slate roofing is known to have been used prior to the revolution.
Archeological excavations at jamestown virginia have unearthed roofing slate in strata dating from 1625 1650 and 1640 1670.
S of chinese slates above and loaded at the railway station below bove many sla leach during acz sts wang w varies as a result of the slate dressing which can lead to stress fractures.
Another common source of slate roof damage around a chimney is wear and movement caused by flashing leaks and in freezing climates frost.
Things like high heat heavy rain and strong winds can also speed up the deterioration of the tiles leaving you with a dull unattractive roof.
In the case of good quality slate these pyrites should not be an issue remaining dormant and unreactive.
However like with most materials these patterns paints and design can begin to fade over time especially when exposed to harsh weather conditions.
Synthetic slate also known as composite includes made of the features that have made actual slate a popular roofing material but it attempts to cut back on some of the drawbacks.
The fundamental weakness such products exhibit is a lack of durability cracking and disintegration and dimensional instability warping and cupping in the presence of water.
A common problem that occurs when using reclaimed materials is that there are simply not enough of the particular tile or slate available from a single batch to complete a roof.
However in cases where the slate is sub standard they can react causing major damage and failure on the roof after only a few years.
Later when the building sagged settled or moved the framing pulls away from the chimney causing damage to the roofing slates and flashing and leading to leaks in this area.
Corrosion can cause nails to snap allowing the slate to slip.
Possibly the most damning indictment of variation in chi nese slate is the con tent of carbonate minerals especially calcite caco.
The original nails used to fix slates were often made of iron or poor quality galvanised steel and will corrode over time.
Wood paper or perlite reinforced portland cement slate and shake products are not suitable for use as long term roof coverings where they are expected to get wet.