Slate roof tiles are made of dense, sedimentary rock composed of clay. Sometimes, metamorphosis will cause volcanic ash to harden into slate. Its mineral structure and density allow for easy cleaving. The cleaved structure is durable and weather resistant.
What are the advantages of a slate roof?
In the 1870s, Europeans discovered the benefits of slate’s quartz and muscovite structure, including:
Its breakable cleavage plane gives it a natural stone appearance while retaining a level surface perfect for stacking.
The smooth surface of slate roof shingles makes it easy for roofers to arrange them in symmetrical patterns.
Slate absorbs water and rainfall with an absorption index of only .4%, making it essentially weatherproof. Because it resists water so well, it is not prone to frost or breakage. Even in cold weather climates, slate provides superior weather insulation.
Low Production Cost
Production cost for slate is not just low in dollars. Creating flat slate roof tile is easy enough that it requires minimal labor. Slate is rare enough that it is still expensive to obtain, but low labor costs save manufacturers and consumers money.
Slate can last for hundreds of years without the need for maintenance. A well-slated roof holds up to unusual weather conditions, including flooding and high winds. A combination of quality slate and meticulous roofing provides a maintenance free roof.
Heat and Fire Resistance
As a metamorphic rock, slate bears natural elements with ease. It reflects sunlight well, providing superior insulation.
It is also resistant to fire, making it a great roofing material for hot places like Texas.
How do roofers slate a roof?
Roofs can be slated with new slate shingles or high-quality reclaimed slate tiles. A knowledgeable, experienced roofing company will follow these steps at minimum:
1. Check the angle or pitch of the roof
The angle at which your roof tilts tells roofers how much overlap will be necessary for your tiles. Roofers have specialized tools for checking angles and leveling, but modern smartphone applications are nearly as accurate.
2. Consider the weather in your area
Places with rainfall and wind speeds that are above average must make special considerations for slate shingles. Roofers will take into account common weather events and make recommendations for slate roofing.
3. Clean rafters or trusses of any obstacles
Rafters and trusses are the support beams that run vertically from your ceiling to the top of your roof. To ensure that slate shingles lay flat on your roof, the rafters or trusses must be cleared of debris such as splinters and old nails.
4. Roll out felt or roofing membrane over the rafters
A roofing membrane, usually made of felt, will separate your roof tile from the inside of your home. Roofers will pull the membrane tight, but will leave a small amount of slack that will collect water that penetrates slate in extreme weather conditions.
5. Position battens and slate tiles
Battens are long pieces of wood that help fasten slate shingles and keep them arranged neatly on your roof. They lay horizontally across the rafters. Roofers establish the pattern of slate placement by placing the first slate shingles before permanently fixing battens.
6. Determine Gauge
Once the first two battens are fixed and the first and second row of tiles has been determined, roofers will determine the gauge of the battens. The gauge is the amount of space between each batten that allows for clean placement of slate shingles.
7. Finish roofing membrane and battens
After finding the batten gauge, the rest of the roof is ready for felting and battens. After all of the battens are placed and the roof is weatherproofed, roofers will lay the slate tiles down in the predetermined pattern and nail them to the battens.
Where does slate come from?
In North and South America, Brazil produces the majority of industrial slate. Brazil is the second most prominent producer of slate in the world. They provide the majority of slate used in the United States. Because the US has to import slate, the cost of the material for roofing rises.
The New England area also produces slate for use in the US. Vermont and New York share an area called Slate Valley that offers a wealth of natural slate. Historic homes in the area helped create popularity for slate roofing in the United States.