real slate vs synthetic materials: A PLACE FOR BOTH

​Let’s begin by me confessing, I'm biased and I absolutely love slate roofs.  I have worked on hundreds of them.  Our SLATOR roof bracket has been used all over the country since 2016 to access slate roofs safely.  Our V-5, V-8, and V-18 permanent anchors are regularly specified on Federal, State, University, and residential projects all over the country.  I simply love slate roofs … when they are installed and cared for properly.

Note:  At the end (scroll to the bottom) of this BLOG, you will find a guide to help you choose the optimal product based on your prioritized values.
 
I just think it’s incredible to take a rock, split it, shape it, and then hang on a roof for a hundred or more years to keep the building dry and beautiful, and … at the end of its life, put it back in the ground exactly the same material as when it was removed.  Talk about cool!  Talk about “green”!  What can possibly be greener than that other than perhaps a “living” roof that also collects water?

​I believe that slate is the finest roofing material ever used since most of us stopped living in caves.  For longevity, it has no proven equal other than perhaps tile roofs in the right environment.  For “value added”, it also has no proven equal, and that's largely why other roofing materials have been manufactured to look like slate.

That being said, I never dreamed that I would come to appreciate what we "in the slate world" call “fake slate” or “mudflaps" (see the 1st photo below and it's easy to see how the first "synthetic slate" earned its nickname).  So, what changed?
 
Slate has not changed.

Man made “slate” has changed.
Slate roofers have changed.
The population has changed.
The climate has changed.
I have changed.
 
Slate has not changed.  Slate was formed (is still forming) over hundreds of millions of years by heat and pressure on the appropriate minerals.  It’s not changing as we perceive time.  Now, veins in quarries may be depleted and the composition of the slate varies from quarry to quarry and even within the same quarry, but, slate was already there, buried in the ground long before we ever took a step.

Man made “slate” has changed.
As consumers, we struggle to balance our desire for quality and economy.  Companies recognize that there is a desire for the look of slate roofs and that most of the population is not willing or able to pay for a new slate roof.  And, realistically, most of the homes built since the 1940’s simply cannot support the weight of a slate roof, yet we still desire the look of slate.

Enter opportunity.
The first companies to manufacture products their marketing departments described as “Better than real slate!” , “Lasts a lifetime!” have mostly changed names or gone bankrupt as the lawsuits piled up and their “slate” curled, faded, and became crunchy on the outside while chewy on the inside.  Folks who paid a premium for a product to look like and “outperform” slate were justifiably mad.  For those of us who tend to be purists and value honesty, it’s left a long lasting bad taste.

​Enter opportunity.
People can learn.  Chemical compounds are developed.  Testing methods improve.  Standards evolve.  Manufacturing processes evolve and today’s products are better than those made by the first manufacturers.  A few years ago I was beginning my traditional metal roofing training with some roofers from around the country.  A fellow trainee was one of the folks known as “stormchasers”.  They swoop into the areas hit by tornados and hurricanes to sell, repair, and replace roofs.  He is accustomed to seeing what heavy wind, rain, and hail can do to even the best roofs, so I asked him,

Me, “What roof is the best?” 

In a heartbeat he answered that it was a “blankity blank slate”

The product he described is man-made and large hail had bounced off it while destroying every other roof in the neighborhood.

Me, “So, you like it better than real slate?

Him, “Absolutely.  I’ve seen them both in the same storm and only “blankity blank” survived.”

I squirmed, fidgeted, unconsciously made a face.  This was not the answer I wanted to hear.  I like “real” things.  I bought my wife a real diamond and I like real slate.  I don’t like vinyl siding and I don’t like fake slate.  But, the crack in my firm position on “synthetic” (another tricky marketing term by folks trying to sell fake stuff) had begun.
 
Slate Roofers Have Changed
When I began my slate roofing journey, I started by finding the best resource that I could find on the subject.  The book, Joseph Jenkin’s The Slate Roof Bible, is in my opinion, still the absolute best starting point for learning about slate roofs.  I learned how important it was to not walk on the slate.  Ten years, and hundreds of roofs later, I have witnessed (hundreds of times) the damage done by roofers, painters, chimney workers, insurance adjusters and homeowners who walk on their slate roofs. 

They’ll say, “You just gotta know how …”, “We’ve ALWAYS walked on them …”, “How else can you get to the broken slate to fix them …” “How else can I inspect the roof …” and other excuses people scourge for like kids combing for Easter eggs.  Yada, yada, yada.  Turns out, some folks don’t learn.
​
Earlier this Summer, I was doing an anchor installation job on a university dorm under complete renovation (including all the slate roof repairs). Step by step, I watched a team of roofers completely destroy a $1,000,000 slate roof that was salvageable (see the photo below).  I’ve witnessed this many times before by reputable and talented companies.  It ruins the reputation of slate roofs and people begin to expect slate roofs to leak.

Yes, you are observant and got it correct.  They wear harnesses but don't practice fall protection techniques like actually hooking the rope to them or keeping the rope tight enough to not go over the roof's edge or collide with the ground.  Perhaps they'll change if they live long enough?

If the slate roof has a "walkable" pitch, expect it to be destroyed by walking.

Above, I'm installing SLATOR-USA's V-18 permanent ridge anchor to safely maintain the roof and fix ... yup ... the leaks from "walkers" and "caulkers".

See the damage foot traffic creates.  Slate is "hung" by two nails and the weight of foot traffic can create cracks between the nail holes and then later the slate breaks, leaks, and eventually slides out of place.

Another job ... first the "walkers", then the "caulkers" killed a beautiful slate roof that was almost 100 years old and could have lasted decades longers.

This roof (circa 1901) was so trashed that I had to replace it completely and cut the slate to match the original design.  Other sections of the roof may still last 30 years, however the hidden gutters will rust out long before then.

Yes, it was expensive.  The excellent slate, from our friends at North Country Slate in Canada was quite reasonable, but I work fairly slowly and it was a lot of labor costs.  I also upgraded the roof by consolidating 3 plumbing vents into our new single leakproof stainless stack (which doesn't need any flashing), adding walkable-removable ridges, adding a V-5 permanent anchor and built-in "slate" steps so hopefully in the future, workers will use them instead of the slate when accessing the flat roof from the upper roof hatch.

Now ... back to our story ...

Slate roofs (here in the USA) have gotten an ill reputation for not lasting, being brittle, being expensive, and for leaking.  The synthetic manufacturer’s recognize this and unfortunately, some continue marketing their product as “better than slate”, “outperforms slate”.  “Better” and “Outperforms” are quite subjective terms that create disputes.

Slate is unchanged.  The material excels when installed and treated properly.  It’s the workers who are changing.  They are not being trained by people who really know the trade.  They don’t know how to set up safe access without walking on the slate, or are often unwilling to take the time.  They are just in a hurry and equate speed with money.  From the informed customer’s long term position, as the installers speed increases, the quality of the installation decreases.  It costs MUCH more in the long run to have a slate roof put down quickly by folks who walk on the slate.

Roofing is a hard work.  It can be extremely cold or hot.  You don't work when it's raining and have to rush, rush, rush when the weather is good.  It can be hard on family life.  Turnover is high, and the body wears out (especially after falling once or twice).  How many old roofers do you see here in the US?  How many folks are still actively roofing over the age of 50? 

In the United States, you don't need a license to be a "roofer".  You don't have to pass an exam such as you do in the plumbing, electrical, HVAC, or general contractor trades.  So, a lot of people, with little to no experience enter the trade because there's always a roof that needs to be fixed and they are willing to work hard.  I know, because that was me ages ago. 

In Europe, roofing is a more respected trade and people go to schools for slate and metal roofing and/or enter apprenticeships.  They might remain in that field, developing and honing the craft until the day they retire.  Just an FYI, you won’t find an asphalt shingle roof in Europe.  Here in the US, roofing is populated by folks who are willing to work hard, but just don’t get the training they need to install or maintain slate roofs properly.  Here, in the US, it’s a young man’s game about speed.  How fast can you nail and how many squares you can install in a day.  Rarely will you encounter someone who develops skills over a lifetime of roofing and retires from the trade at retirement age. 

The crack in my "purist" slate only mentality widens as I consider which roof is more forgiving to foot traffic and lower skill set workers.
 
The Population has Changed.
In 1940 the US population was about 130 million and today the population is over 330 million.  There are not enough workers or enough slate available to make each steep pitched roof a slate roof and there never will be.  There are not enough skilled workers or slate available to slate the roofs of every homeowner who wants their roof to look like slate, and there never will be.
Today, statistics show that people in the US move every 7 years.  Homes that used to be built to stay in a family for generations are rarely built.  If you want a roof that will last generations, then slate is a proven answer (assuming it is not destroyed by unskilled workers).  If you just want a nice looking roof because you will be moving … and you know it, a synthetic roof might be a better choice
 
The Climate has Changed.
Whether you believe that the climate has changed or whether you don’t … doesn’t matter.

There is no disputing that Insurance companies are all about data.  Accurate data, along with prudent decisions leads to consistent profit.  Insurance companies cannot stay in business without making a profit (Who can right?).  So, they crunch numbers, and more numbers, and more numbers until they know that … in order to make the profit they desire, they need to raise premiums and/or pull out of areas that are unprofitable.
What are the leading causes of roof damage covered by insurance?  Wind.  Hail (falling objects).  Fire. 
 
Wind:
One of the synthetic roofing material manufacturer’s, BRAVA, warranties their product to winds up to 130 mph and has tested their system up to 211 mph.  They can achieve this because of their product design, consistent manufacturing technique and installation methods of either using ring shank nails or screws.  I don’t know of any wind testing for slate that can begin to achieve this.

I repair slate roofs for a living and it’s just not feasible for a slate roof to have a wind rating because of product variations (slate is a natural product and split along grain lines to achieve the desired thickness) and how they need to be installed.

Slate is “hung” by nails, not compressed by the nail.  "Overnailing" (driving nails in too tightly) can crack the slate or make the bottom of the slate elevated (looking awful) and giving it a bigger edge to catch wind.  Ring shank nails are absolutely incompatible with slate roofs because they often get driven in too tightly (ruining/cracking the slate) and making repairs extremely difficult.  They won’t help with much wind resistance either because the nail holes in slate are punched (not drilled) for the nail head to recess just below the slate’s surface.  Slate will just blow off and leave the nails behind with a strong enough wind from the wrong angle.  What that wind speed, duration and angle are necessary to remove slate depends on each specific situation.  Assuming the nails are driven properly into solid wood (not OSB, not ½ plywood, and preferably real old school wood), slate’s wind resistance relies on its shear weight, beveled edges, overlapping layers and a good/steep roof pitch. 

Impact rating:
Well, I just don’t argue with properly collected data by insurance companies or eye witnesses.  The storm chaser (mentioned earlier) has witnessed how hail destroys roofs much better than I have.  Synthetic materials are consistently made, tested, improved, retested, tweeked again, and retested until you have achieved the optimal/acceptable degree of the hardness and impact absorption you desire.  Slate doesn’t change.  Man made products do change as the flaws are recognized and minimized by redesign.  That's good.  This same process has moved our traffic mode from bare feet to airplanes.  I still like both very much ... depending on my goals of the day.  So, if you desire an impact rating, live in hurricane or hail prone areas, a synthetic material is worth considering.

Fire:
Ok, so take a moment and do some research.  Type in “fire rating of roofing materials”.  It’s pretty interesting.  Class A is currently the highest rating for resistance.  Basically, what your research will find is that slate is not going to burn.  And, maybe equally important, it is not going to melt.  When the embers blow from the fire and land on your roof, this will be important.  If you happen to have a synthetic roof, and there’s a fire next door, be thankful of your Class A rating and hopefully your building survives, but I’d still expect to have to replace the roof.

Generally, I’d prefer slate for fire resistance but there’s a small window for me to change my mind.  The irregularity of the slate surface allows water that gets under slate to easily get out.  This is how it is supposed to work and one reason that a slate roof can last for over a hundred years.  Untrained handymen, roofers, and DIY’rs who attempt to fix leaking slate with sealants … simply make matters worse in the long run by locking moisture in. 

How does this apply to a fire rating?  I don’t know … but forest fires are brutal and embers get blown into tiny places where we don’t want them to go.  The compression of synthetic materials held tightly together by ring shank nails or screws may reduce the opportunity for embers to be blown into crevices.
 
Summary:
I’ve changed.
Once I was young and knew everything.
Now, I’m old and know that I don’t.

There’s lots to consider when choosing a roof material.  Here’s a flow chart that may help you weigh the pros and cons of choosing between natural slate and any synthetic material.  There’s a right time and place for everything.  

Basically, what I've observed from hundreds of clients over decades is this:

1.  Nobody wants their roof to leak.

2.  Nobody wants their roof to be a headache.

3.  Everybody wants their roof to last a long time.

4.  Everybody wants their roof to require little to no maintenance.

5.  Some people also want their roof to also be beautiful ... but don't tell the solar installers this because they'll just look at you funny.

Author: Ronny Roseveare (founder Slator, LLC and Blue Glass, LLC, and Petzl Technical Partner) designs, installs, and trains roofers how to utilize steep pitch fall protection systems.  Here, he installs a custom stainless steel access hatch in the top of a dome that included (16) OSHA compliant anchor points for the roofers (The Roofing Company - Hampton, VA) to safely re-roof this dome.  Anchor in.  Live long. 

learn more about the project in the photo above

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