Natural or Synthetic Slate?

Foremost, slate is formidable stuff. A slate roof that has been installed and maintained correctly can last for a century or longer. In some cases, the roof – at least the slate – can outlast the building itself. As such, it is common to salvage slate and recycle them into another roof or project. This helps to keep slate out of the garbage dump, making it among the most environmentally friendly options, as compared to asphalt or synthetic slates which have shorter life spans and no recycled value. Once they’re time is up, into the dump they go.

Synthetic products are mass fabricated and do not present the same way a natural slate roof does. The tiny individual variations in each tile – the color, striping, edge, and shape – are woven into a roof that tells a unique story about that building, its unfolding history, and the land itself. Plastic shingles are versatile, but unromantic and less durable. There’s no poetry, no story. It’s a plastic coating; cheap simulacrum.

In contrast, natural slate is authentic historicity and modernity; a deep look into the past and a bold step into a lasting future. It’s not a me-too product. Slate roofs are timeless, thoughtful, and a testament to human ingenuity. A nod to a time when things were built to last.

Sometimes they still are.

Surviving for a century or longer takes a formidable material. Slate is naturally fire resistant – making it great for drier, more fire prone climates – while acting as a natural insulator that can help to regulate your home’s internal temperature. And thanks to its density, insects cannot burrow into slate to lay eggs, deterring them from breeding there.

But longevity is also a function of maintenance. Anything left outside will need to be cleaned and patched up from time to time and slate roofs are no exception. Acts of God, like heavy branches, hail, and other intense weather can damage a slate roof. Thankfully, most slate repairs are relatively minor – a shingle cracked, missing, or askew – and can be repaired fairly easily. In general, it’s worthwhile to have your slate roof inspected annually, to catch small problems early. A slate roof is only as strong as its weakest shingle and issues detected early will save you considerable hassle and heartache. In general, though, a well built slate roof is about as effortless as one can expect from something that protects your home and all of your valuables from the ravages of time.

It’s worth repeating that a slate roof must be installed by a capable specialist. While slate is a resilient material, its incredible longevity as a roofing material depends on the skill of the roofers who installed it. Small missteps or cost-cutting short-cuts will require maintenance or repair far sooner than a job done correctly, once.

Sharon Park, FAIA, senior historical architect for the National Park Service Technical Assistance Division, suggests contacting your local historical commission, if there is one, and with your State Historic Preservation Office to ask about possible substitute slate for your roof. 

This is required if you plan to cash in on tax credits for home rehabilitation in states that provide them.

The fact is, nothing beats the durability and aesthetic value of a natural slate roof. It takes regular evaluation by an expert to uphold the quality and appearance of a natural slate roof. Winter can be an especially harsh time for a slate roof if it did not have the proper underlayment put in upon installation.

Since the majority of people were not the homeowners when their slate roof was installed (they can last up to 100 years or more), it is something all homeowners should get checked out. Having the proper underlayment and high-back gutters can prevent thousands of dollars worth of water damage later on.

Below is a picture of a relatively new synthetic slate roof. If you look closely you can see many of the tiles have curled. This would never happen with the use of natural slate.

If you haven’t already, you really ought to network with local restoration architects and contractors, especially those familiar with your area. In order to maintain the historical integrity of your home, all repairs should be done with materials that match the originals as closely as possible.

Natural slate has been used to roof buildings for a millennia and was brought to the New World by European settlers where the practice of slate roofing expanded significantly. Nothing at the time – and nothing since, engineered or quarried – has been able to match the durability, essential beauty, and fire-proof qualities of natural slate. Many manufactured products have tried, but true, natural slate triumphs as a roofing material every-time.