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2 Reasons Why Your Slate Roof May Fail

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If you own a historic residence, then you may be surrounded by ornate beauty. This may include the roof if a slate construction was utilized to form the top portion of your home. These roofs can last between 40 and 200 years. However, if your roof appears to be deteriorating well before the 200 year mark, then a replacement or repair may be in order. To better understand why this may be the case, keep reading to learn about two common reasons why a slate roof may fail.

Failure of Materials

You may wonder why one slate roof can last for only 40 years or more while another can remain strong after 120 or 200 years. Usually, this comes down to the types of materials that were used to create your roof. Slate comes in two different varieties, soft and hard. Hard slate is likely to last much longer than soft varieties, and it generally has a colored appearance, unlike dark black soft slate. If you have a historic home, then the longevity of your slate roof can be linked directly to the quarry where the shingles were originally created. At present, slate shingles are still being produced in Pennsylvania, New York, Virginia, and Vermont. There used to be quarries in both Maine and Georgia, but they are no longer in operation.

Slate Types and Features

Here are some distinguishing characteristics that can help you figure out the type of slate your roof has:

  • Vermont slate - Many older slate materials used on roofs were formed from either a sea green, pale green, or a purple color. This slate is the hard variety, and likely to last around 150 years or more. You may see some fading though, especially if you have some of the green tiles. Generally, the fading produces a pale gray color.
  • Pennsylvania materials - Most of the slate that came or comes out of these quarries is a dark gray or black color. There are a wide variety of quarries in the state, and each quarry produces slightly different shingles with varying colors and textures. In general, the soft slate is likely to remain in good condition for at least 75 years. These materials are similar to the ones quarried in Virginia.
  • New York slate - Slate shingles made in New York usually feature a distinctive red color, and these materials are of the highest quality. The hard shingles can last up to 200 years.

If your roof features red, purple, or sea green slate tiles, then it is likely quite easy to figure out where they can from. If tiles are a dark gray, black, or another muted tone, then it may not be so easy. Contact a roofing contractor to help figure this out. Once you know where the shingles came from and their approximate life expectancy, you can understand why your roof is failing and whether or not it is best to have it restored or completely rebuilt. For example, it may best to restore or repair red tiles, but you may want to fully replace black or gray ones that are starting to deteriorate.

Deteriorated Flashing

When your shingle roof was first installed, flashing material was constructed in between each section or plane of the roof. This helped to keep water out of the joints. Often times, copper was used, and this soft metal will start to corrode, pit, and generally fall into a state of disrepair much sooner than the shingle materials themselves. Coated steel may have been utilized too. Painting can prevent the steel from corroding, but poor maintenance over time has likely led to the deterioration of the metal. 

As the metal flashing deteriorates, water is allowed to leach under the tiles. This can cause the slate itself to wear down quicker, and the asphalt, felt, and wood underneath the shingles can rot and wear too. If you see flashing issues, then ask your contractor to replace it and also inspect the seams of the roof and the various layers of roofing materials around the areas. If damage is not too severe, then minor repairs and slate replacement may be required.

For more information, contact roofing contractors in your area. 


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