What is Slate Roofing?

Do you need to replace the roof? Are you ready to give asphalt shingles the heave-ho? Does your municipality not approve wood shingles? Slate roofing might just be the material to consider. Bold and muted color combinations allow for the unique character of your home to shine through — even long the roofline.

What is Slate Roofing?

The National Slate Association gives a bit of background on the material. Slate is actually a metamorphic rock comprised of minerals and clays that has been exposed to extended periods of pressure. Slate for roofing is a material that took considerable time to form. Geologists pinpoint slate formation to have taken place between 435 and 570 million years ago. It is interesting to note that slate makeup varies by quarry location; the minerals that were present at that time of material formation directly influenced quality and color.

Slate Roof Color Variations

You are probably quite familiar with the gray tones that dominate commercially available slate roofing materials. If you are in the market for something unique, consider the black slate coming from Northeastern Pennsylvania quarries or Vermont’s purple variety. Green slate can be traced back to New York quarries, while Newfoundland is famous for its variegated green and purple colorings.

Be careful when picking out the slate roof color! Another feature of this material is its availability in weathering and unfading varieties. New York’s red slate is sold as “unfading,” Vermont’s gray and green slate roof tiles are sold as “semi-weathering.” Expect the latter to change color — after exposure to sun and elements — to various shades of brown. Ask your roofing contractor to show you weathered samples of the material you are considering.

How expensive is Slate?

Roof size matters; Consumer Reports explains that the various types of roofing are sold by lots of 100 square feet. After multiplying the lengths and widths of the roof sections, be sure to add another 10 percent for broken or wasted shingles. If you divide this figure by 100, you can estimate closely the number of lots (or squares) you need. The average single family home calls for approximately 30 lots.

Add in labor costs, which vary depending on your local going rate for master slate cutters, and the figure continues to rise. Next is the material cost. If your standard roof replacement with asphalt shingles costs about $5,000, plan to spend an additional $30,000 just for standard slate. If you get fancy with the color variations, the price tag may get steep. Case in point is the unfading red slate roofing, which is more expensive than your average gray.

Can your Roof handle the Weight of Material?

Slate is heavier than asphalt shingles. Reinforcing the attic structure may be a necessary step of the planned roof replacement. The ASHI Technical Journal points out that slate roof application calls for tile thickness variations between 3/16 and 1/4 inches. A seasoned roofer with an appreciable experience in the installation of slate roofs should advise you with respect to the types of shingles that will be most beneficial – and safest! – to install on the existing structure with minimal alterations thereto. If you desire slate and have a compromised attic structure due to beam material choice, termite-, or dry rot damage, be prepared to spend a hefty sum on upgrades.

Now that you know about the increased cost of slate roofing, remember that the material is exceedingly durable. The types of slate coming from Virginia’s quarries (the ASHI Technical Journal identifies them as the “Buckingham” line) may offer roof protection for about 175 years. Vermont roof tiles have a longevity that falls between 100 and 200 years. The again, Pennsylvania slate only offers a 40- to 50-year lifespan. Choose wisely!


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