Endangered Species: DC Slate Roof

What lasts for decades, protects your home, beautifies and characterizes a neighborhood, and is natural? A slate roof. But as the homes in our older neighborhoods start to need roof replacements, many people are opting for cheaper asphalt roofing.

I think this is a shame. In caring for my own slate roof, I have learned a few things, like the “greatest enemy of slate roofs can be roofers themselves.” Below is some of what I have learned, in the hope of helping home buyers understand the value (and costs) of a slate roof in their potential home. I also hope to convince at least a few people to maintain their stone. And, for those who definitely need roof replacement, maybe they could look into some fake slate alternatives? 


First, about slate
 (I am no expert but this may get you started):

  • Realtors may tell you that a slate roof “has a 50 year expectancy” and so you make plans and assumptions based on that.  In reality, that should be a minimum and it depends on the type of slate and the condition of the roof. My roof is 60 years old and still going strong. One slate roof expert told me a well-maintained roof can last 120 years (or even much more.)
  • Good maintenance means having a roofer experienced with slate check the roof and replace any damaged slates each year (or so.) Of course this costs money, like maintaining any part of your house. 
  • Good maintenance means you are protecting the wood underneath the slate, which is equally important to determining the longevity of your roof. 
  • Not all roofers know how to handle slate properly, even if they say so. Some apparently find it easier and more profitable to tell you that you are in need of total roof replacement (with their chosen asphalt, of course.) Know what questions to ask about their methods, and get someone you trust. The best place to start learning is a Web site called Slate Roof Central. It is for contractors, really, but individuals can learn a lot and get a checklist of questions.
  • You can save money by buying your slate directly from a quarry (I did this for my front walkway and saved about 60% on my stones compared to the local garden center.)

About fake slate alternatives:

  • Some of it looks good and passersby are unlikely to notice the difference. Fake slate may save you money compared to a new slate roof, and it can be environmentally responsible: e.g. my architect friends used recycled rubber shingles that look like black slate.  
  • Not all fake slate looks good and it is not all as long-lived as you’d expect. Here is a very interesting conversation string between an expert, some contractors and some homeowners. 
  • The MAIN MESSAGE is that the material is less important than the installation methods in determining the life, looks and value of your roof. The method also affects the cost, whatever the material.
  • Here’s one person’s positive experience from “This Old House.

As a final note, while I am generally on the fence about extending historic preservation rules to more and more neighborhoods (because of the burden on homeowners), the roof issue makes me stop and think. The disappearance of the slate roof can alter the charm and character of an entire street. Since I can live with many other architectural changes, I wish our historic preservation rules in DC were a bit easier and less all-encompassing. Perhaps some of you have something to say about it …. 


  • http://urbanplacesandspaces.blogspot.com Richard Layman

    wow I didn’t even remember writing that piece. What do you think are the particularly onerous aspects of preservation laws and regulations now?

    Re your other point, there is no question that in each field of craft (roofing, plumbing, carpentry, windows, etc.) there are people attuned to historic housing issues, like your slate roof, or not.

    In another house, we had great experience with a plumber to fix a boiler, broken water main connection, and replace a water heater.

    We just moved to a 1920s bungalow and needed some preservation-sympathetic plumbing sensibilities and it turned out he is completely out of his element…

    (It’s not as spectacular maybe as the 1718 Webster St. NW house, but then, we don’t need 7 bedrooms, there are just two of us, although I like that garage. Ours needs serious work…)

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