Fieldnotes: Slate Roof

Filed-notes: Slate Roofing

Durable and Timeless Roofing

Slate roofing demonstrates the power of nature that formed it, the industry that shaped it, and the craftsmen that laid it on the roof! Because of the craftsmanship, environmental impact, and expense, all efforts must be made to repair rather than replace. Slate roofs can last lifetimes, up to two hundred years! The National Park Service recommends a regularly scheduled maintenance program.

COMMON PROBLEMS

Why do tile roofs fail?

Tile roofs fail because of natural factors and installation. Typically tiles fail for three reasons, physical properties, flashing failure, and breakage.

Physical Properties: The most common failure of slate tiles is the natural properties of slate and how it deteriorates in response to common weather conditions. This process happens slowly over decades and allows moisture to damage framing without showing obvious signs of leaking.

Flashing Failure: Original flashing around plumbing penetration, valleys, and chimneys may be rusted or corroded. This can lead to homes in highly vulnerable areas.

Breakage: Many things can cause breakage, tree branches, frost and freezing, and careless foot traffic on the roof. Breakage can lead to water infiltration, which will result in framing failure.

The ability to lay slate properly so as to produce a watertight and aesthetically pleasing roof requires training, much practice, and the right tools. The installation and repair of slate roofs should be entrusted only to experienced slaters.
— National Park Service

Maintenance

How do I maintain my slate roof?

Given the high cost of a new slate roof it is essential to maintain the slate roof. First, annual inspect the roof and inspect after any significant storm event. Inspections should be done using lift equipment or a drone. Second, remove all debris and tree branches that may be touching the roof. Third, have the gutters on the home cleaned twice a year... even if your gutters have leaf guards.

Repair 

How do I repair my slate roof?

An experienced slater should complete slate roof repairs:

  1. A contractor must take special precautions not to cause additional damage.

  2. All structural repairs must be complete before missing or broken tiles are repaired.

  3. The roofing professional should replace broken slates with salvaged or replica tiles.

Replacement

When should I replace my tile roof?

Slate roofs should be replaced when the repair of flashing, framing, or deteriorated shingles will exceed 50% of the overall surface area. If a replacement slate is required for the project, it should match the original shingle as closely as possible since an original slate roof is likely to be one of the building's most significant features. In addition, slate roofs have the inherent variations, texture, and color that are so important in defining the home's character. Thus, only traditionally shaped shingles are appropriate for replacing a historic slate roof.

What does a new tile roof cost?

The cost of a new slate roof can easily exceed $200,000 on a typical home.

Old Home Rescue is Oklahoma's only general contractor that specializes in traditional and historic exteriors. Please contact us to begin restoring and remodeling your home's unique exterior character.