Slate is a highly durable stone that has been used in roofs for centuries, but was almost completely replaced by asphalt in the 20th century. Now seen primarily on churches, historical buildings and older homes, slate offers a natural, prestigious look and a long lifespan that appeal to many buyers. Slate roofing is also quite low maintenance and is invulnerable to fire, insects and rot. This material is relatively expensive, however, comes in a limited color range, and is extremely heavy. This material should be maintained only by a professional.
Natural slate roofs provide an elegant beauty that no other material can match. The natural variations in the slate tile create an appealing look from a distance that makes a slate-roofed building stand out from neighboring asphalt-roofed structures. Slate roofs are an excellent choice for vintage homes, ecologically-friendly structures and historical restorations. They complement brick and stone architecture well, but can be used on just about any kind of home.
Slate is an extremely durable, long-lasting roof material that is rivaled only by tile. Roofing tiles made from this stone absorb very little water, making them excellent at deflecting rain and avoiding frost damage. The average slate roof will last 100 to 150 years with correct installation and occasional maintenance. Many slate roofs have been in place for even longer, requiring only occasional re-flashing and tile replacement.
Roofs made of slate tiles also resist fire better than asphalt or similar roofing materials. They never rot or develop mildew and they are impervious to insect infestations, unlike cedar shakes and shingles. When treated with chemical sealants, slate roofs are also resistant to efflorescence, stains and moss or lichen growth, though some homeowners see these features of the natural aging process as desirable.
Installing a new slate roof can be relatively expensive, at between $10 and $40 per square foot, or about 10 times the cost of a similar asphalt shingle roof. Slate costs 1 1/2 to 4 times more than wood shakes or shingles, 3 to 4 times more than clay or concrete tile, and 2 to 3 times more than metal roofs, including copper. Its actual cost of ownership over the course of the roof's lifetime is far lower, however, since most other materials need to be replaced frequently. Asphalt roofs must be redone entirely every 20 to 35 years, for instance.
The actual slate tiles can be secured to the roof using one of two ways. The most common technique is nailing with copper or stainless steel into a timber batten. It's also possible to attach the slates to the roof using special hooks, which make no holes in the slate and produce fewer weak areas. This method provides better support in areas with severe weather conditions as the wind is less likely to blow the tiles off the roof. Hook fixing also makes it easier to put slate on unusually-shaped roofs, since it allows for smaller tiles, but this technique is somewhat more expensive than nailing.
One of the biggest drawbacks of slate roofing is its weight. This material can weigh 800 to 1,500 pounds for every 100 square feet. That means that it requires an extremely strong roof structure to support it effectively. Many modern homes must be reinforced to carry the extra weight before a new slate roof can be installed.
Another common disadvantage of slate is its relative fragility under pressure. This material can last for centuries, but breaks easily when walked on. If you install slate on your own roof, you may need to have basic maintenance performed by professionals who know how to walk on the tiles without damaging them. This can increase the difficulty and price of maintaining your slate roof.