How Long Will A Slate Roof Last?

How long will your slate roof last?

A typical slate roof will last 80-200 years. Hard slate will last for a much longer period while softer slate will not last as long. Other factors such as weather and foot traffic on the slate tiles can have a big impact on how long a slate roof will last before needing repair or replacement. 

What factors influence how long a slate will last?

Not all slate is the same. There are many characteristics that make up slate used in roofing that will determine how long it will last before it is no longer functional. Of course there is no way to tell exactly how long an individual piece of slate will last, knowing if the material is hard or a better quality will help provide a clue as to a range of years that it may be functional. 

For example, there are certain buildings in Europe that have the same slate roof for more than 400 years. And they still do their job! 

Type of slate (hard or soft) – One feature that has the biggest impact in how long slate will survive is the hardness. A hard piece of slate will significantly outlive a softer piece of slate. 

Origin and quality of the slate – In the United States, slate that comes from New York State and Vermont tend to be the best quality. While much of the slate from Pennsylvania has many fine qualities the lifespan tends to be much shorter. Slate is graded by the ATSM with a rating of S1 being the highest quality.

Climate / weather – Slate that is exposed to constant heat, cold or heavy rain and hail tend to not last as long as those used in milder climates.

Roof pitch – Sometimes the pitch of the roof or the number of facets can allow added pressure from weight of the slate or snow accumulation that could wear it out faster.

How to tell hard slate from soft slate?

There are a few ways to tell if a slate is hard or soft to help indicate how long it may last. One of the best ways is to find out where the slate was sourced from. Lots coming from one location will be easier to determine its quality.

One way to tell that slate is a hard stone is by the color. Slate that is black will typically be softer than slate that has a tint of color such a red, purple or green. Color usually indicates minerals within the stone that provide strength.

Another test is to give the slate a tap with your knuckles and listen carefully for a true ring. If the tone is flat it may be a softer or lower quality slate.

A visual inspection of slate that shows a vertical grain from the top to bottom will help identify the piece as harder. Similarly tiles with large or frequent inclusions (marks that stop the smooth flow of the pattern) are likely to be softer slate.

Other factors that impact the life of your slate roof

In addition to the quality and use of the original product, there are other factors that can prematurely weaken slate. These can lead to reducing the life of a roof. Most are human factors

• Proper installation – When you have a roofer who is truly experienced with installation of state you will undoubtedly get a better result. When an installer takes shortcuts or uses inferior products to hang slate, it can certainly impact how long it will last.

• Proper maintenance and upkeep – By keeping a roof in tip top shape with routine inspections and repair that take place soon after damage is identified will lead to a much longer lifetime.

• Walking on the slate – Anytime someone walks on a slate roof you have a chance to weaken the tiles. Whenever possible, inspections should be done with a ladder, binoculars or a drone. Repairs should include proper precautions to avoid damage to the slate.

• Flashings – Most slate tiles will often outlast the metal flashings, clips and nails holding them in place. When these become misaligned, slates can bang together, fall off and break.

• Environmental Factors – Sometimes sudden storms like we get in Northern New Jersey can cause tree limbs or debris to crash onto a slate roof with untold damage. 

Signs a slate roof may need to be repaired or replaced

There are some obvious tell tale signs that a slate roof needs to be repaired or replaced. Often the first warning you get is a small water leak. That is when it is time to call a professional such as Hart & Sons, Inc. who can accurately assess the problem and propose the best solutions that will work for you.

Sometimes a slate roof needs repair but you don’t get a warning sign. The best way to determine this is from routine inspections. Typically the roofs of commercial buildings have regularly scheduled inspections. If not, a roof leak could damage inventory, equipment or stop operations. The roof of a personal residence does not usually get checked out until there is a problem. Use binoculars from across the street, stand on a ladder to see the roof clearly, or use a drone with high definition video for an accurate inspection.

Some issues you find may find with a slate roof include:

Fragile chips and slivers of slate usually along the edges. When this is spotted, try to determine the extent of the decay. Is it all in one spot, or do you notice this across the entire roof. 

Visibly missing tiles are usually easy to sight. You will want to get this condition remedied right away so water does not penetrate the wood causing a much larger issue.

Water leaking in your home or even just excess moisture appearing in the attic can signal a problem that should be addressed right away. 

Dips, warping, or uneven rows of slate can signal  your roof has been compromised for a longer period of time. 

Cracked tiles can allow water to penetrate to the wood below. Small cracks can be tough to spot by an untrained eye, but catching them before they become larger can keep a repair on the smaller side.

Localized damage from a storm such as a tree branch that fell on your slate roof should be checked out by a professional. The branch can be carefully removed without causing residual damage and a proper inspection can be completed to identify any repairs needed. 

Not sure if your slate roof can be repaired?

Most slate roofs in Northern NJ towns such as Maplewood, Westfield, Summit and Plainfield will only require a simple repair when damaged. Even when a lot of slate on your roof is misaligned due to an underlying problem, the existing slate may be able to be reused and can last for decades. 

Our team has extensive experience working with slate roof repairs in New Jersey. In fact, we have one of the largest inventories of slate roof shingles in the Northeast United States. That means we will be able to better match missing tile to your existing slate roof than anyone. 

Call Hart & Sons, Inc at (973) 761-7676. We have offices in Maplewood and Plainfield and are ready to help you.