Cost of installing a slate roof

    Photo: hotblack/morguefile.com

    No matter how you cleave it, slate is a high-end roofing material. It's also top-notch, in terms of quality, durability, fire-resistance, appearance and, to be technically precise, architectural awesomeness. Does all that mean slate is totally out of reach? For most homeowners, absolutely. But it's just possible that installing a slate roof can be more affordable than you might think. However, perhaps a better question to ask is, do you even want slate to be more affordable? A slate roof should be a once-in-a-lifetime investment (not counting maintenance costs) that potentially pays off for generations. When you think of it that way, cutting corners on materials or workmanship isn't exactly a timeless idea.

    How Roofing is Priced

    Most roofing materials and installation are roughly priced by the square, which is 100 square feet of installed roofing. It's important to note "installed," because with shingle-style roofing more than half of the raw material is hidden, due to the overlap between rows, or courses, of shingles. The portion of an installed shingle that's visible is called the exposure. You might also hear the term headlap; this is the amount of overlap between three successive courses, or how much shingles in the third course overlap (indirectly) the shingles in the first course. Material pricing on standard slate shingles typically assumes a 3-inch headlap. In addition to materials, the cost of installing slate roofing is based on many factors, such as the roof's size, type (shape), slope, accessibility, design features and related elements like chimneys, dormers and gutters. Flashing and other metal elements can add significantly to a slate installation because the material of choice here is copper, and copper ain't cheap.

    So…How Much?

    You've probably heard the joke about truly luxury items: If you have to ask how much it costs you can't afford it. This doesn't exactly apply to all slate roofing, but prices can easily climb into the "don't ask" range. At the low end, slate shingles can run about $400 per square. In the middle range, $600 to $1,000 per square is realistic. And it goes up from there—$3,000 per square is not unheard of. Costs of installation vary based on the factors mentioned above, as well as the skill and experience of the installer. (Tip: When you're paying this much for the material, you want a slate specialist to install it.)

    All told, the cost of installing a slate roof can range from about $1,500 to over $5,000 per square. On a 30-square (3,000 square-foot) roof, that's a price tag of $45,000 to $150,000 for the whole job.

    Now, back to the question of affordability, or more precisely, relative affordability. Even if you use the cheapest slate and the cheapest installer you find (who could be a good builder but doesn't really know slate), the cost of installing a slate roof is still well into the high end of the roofing spectrum. Yet, that lower-quality stone and improper installation will surely lead to problems, so you've just spent a ton on your roof and it has the same problems as a hacked-up job with cheap asphalt shingles.

    What Makes Slate So Great, and Pricey?

    A properly installed and maintained roof of quality slate can last 150 years. That means if you're looking at a historic slate-roofed home standing today, the majority of the shingles could have been nailed down during the Civil War. That's a lot of rain, snow, sun and windstorms. Over the same period a wood or asphalt roof might need replacing five or eight times. Slate roofing requires not only skilled, knowledgeable installers; it also needs good decking (slate specialists recommend solid-wood decking, not plywood or other sheet goods) and a strong roof structure. Slate shingles can weigh 800 to over 3,000 pounds per square, compared to about 250 to 450 pounds for standard asphalt (composition) shingles. Of course, any structural modifications or new decking add to the cost of installing slate roofing.

    Hybrid Slate

    In truth, there's no such thing as "hybrid" slate; that's just a descriptive name for a newfangled product designed to make slate roofing less expensive, or at least competitive with imitation slate products. The trick is in the hybrid shingle, which combines real slate tile with a synthetic waterproofing material; when the shingles are installed with the usual overlap, the real stuff hides the synthetic portion. This design makes the roofing considerably lighter (about 550 lbs. per square) than traditional slate, making it suitable for many homes with standard modern framing and decking.

    The cost of installing this kind of slate roof largely depends on the slate material, which comes in various colors and types, just like standard slate tiles. According to hybrid shingle manufacturers, installation is less specialized than with traditional slate, and therefore potentially less expensive, but it's advisable to use someone who's installed plenty of these roofs before. Will a shingle that contains synthetic materials last as long as traditional slate? Only time will tell. Just keep in mind that when it comes to longevity, it's very, very hard to beat stone and copper.

    Philip Schmidt writes for Networx.com.

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