How Long Does a Slate Roof Last?

Slate is a fantastic natural roofing material that can offer a unique rustic appearance to any property. But, slate’s good properties aren’t only aesthetic; it is also a very durable and long-lasting roofing material if properly maintained. We look at how long your slate roof is likely to last.

How long does a slate roof typically last?

Slate is an exceptionally durable material because it has a high resistance to frost damage and a low level of water absorption. This means that slate is less susceptible to leaking or cracking caused by water damage than other roofing materials.

Naturally formed in sheets, slate can be easily split to make tiles without weakening the material. A natural slate roof typically lasts anywhere between 75-200 years depending on how well it is maintained. The roof should keep a consistent appearance over its lifespan too because of slate’s natural weatherproofing, and it won’t noticeably fade the way that traditional tiles will.

What affects the lifespan of a slate roof?

Type of slate

Whilst natural slate has a very long lifespan, as mentioned above, this is not the only type of slate on the market. There are also a couple of manufactured alternatives – man-made slate and fibre cement slate.

Natural slate lasts the longest of these three types – the other two types both use slate mixed with other materials (such as cement and synthetic resin) to make them cheaper but still give a slate-like aesthetic. Both fibre cement slate and man-made slate have a lifespan of around 30 years.

Quality of the slate

Even natural slate comes in different qualities. Even that figure we presented earlier, 75-200 years (which is just an average), has a huge range within it. Different types of slate from different quarries in different countries have distinct characteristics and, as such, affect how long the slate roof will last.

The slate must go through quality control tests to determine its grade, and it is the higher-grade slate that lasts the longest.

Quality of the installation

How well the slate roof has been installed will also affect its lifespan. Older slate roofs were installed with iron or lower-quality galvanised steel nails that are very susceptible to weather corrosion, causing a problem called nail sickness. Slate roofs suffering from nail sickness are likely to have slipped and broken slates that allow water damage and reduce the lifespan of the roof.

Other common installation problems that can affect the lifespan of a slate roof are inadequate overlap of the tiles, poorly fitted flashing and poor sheathing materials in the roof underneath the slate.

Walking on the tiles

People getting up on the roof to conduct repairs may happen from time to time, but this can severely reduce how long a slate roof will last. Any work conducted on a slate roof should have the workers using ladders and roof scaffolds, not stepping on the slate itself. Stepping on the tiles will compromise their strength, and also put undue stress on the fixings, making it more likely that the slates will prematurely slip or break.

Damage from overhanging trees

Overhanging trees present a couple of major problems for slate roofs. For one, they provide consistent areas of shade that prevent the roof from drying out properly and allowing the growth of moss and mould. The other problem is the danger caused by falling debris like broken branches, which can damage or break the slate and cause the slates to slip and come loose from their fixings.

Maintenance or lack of maintenance

The final factor that affects how long a slate roof lasts is how well it is maintained. Proper maintenance of a slate roof requires regular inspections of the roof to identify early warning signs such as damage to individual slate tiles, slipped slates or faulty flashing. It’s important to get these problems fixed rather than ignoring them. Even these small issues will become big problems if they are not addressed early.
If you need help installing or repairing your slate roof, please get in touch and see how we can help.