Replacing Your Historic Roof And What You Need To Know
In a typical roof replacement, your roofing contractor will remove and dispose of the old roof, then replace it with new shingles. A historic roof replacement is a bit more complicated. In many historic homes, the roof defines the architectural character of the structure. It characterizes the home’s style and contributes to the building’s aesthetic. Think about the graceful slopes of the Shingle Style, the turrets of a Queen Anne, or a stately Mansard roof. All are great examples of how the roof is a major design element.
A weather-tight roof is a critical structural element for the preservation of a building, regardless of its size, design or age. No matter how decorative the form or durable the materials the roof will eventually fail. In a historic home, a failing roof will accelerate the deterioration of historic building materials like masonry, wood, plaster and paint, so fast action is necessary.
Historic Roofing Materials
Historic roof repair can be challenging because a range of materials may have been used depending on the style, design, and era of construction. In many locations, preservation societies, or local building codes define the materials used to repair or replace a historic roof.
Here are some common historic roofing materials and how they tend to deteriorate over time.
The first European settlers used clay roofing tiles as early as the mid-17th century in the Americas. Later, cities including New York and Boston used clay roofing as a precaution against fire. Clay tiles often crack or break when hit by tree branches or if they are walked on improperly. Low quality, improperly fired tiles, will craze or spall as an effect of repeated freezing and thawing.
Historic roofs come in a variety of metals including lead, zinc, copper, tin plate, teme plate, and galvanized iron. Metal roofing is aesthetically beautiful and durable. However, metal roofing can deteriorate over time from pitting and streaking caused by airborne particles, acid rain, lichen, moss, or alkalis found in lime mortars. Metal roofing can also fail due to sheet metal fatigue, or corrosion from galvanic action.
Sheet metal fatigue is a result of repeated stress. For example, the long-term effects of wind and rain lead to the metal weakening where it’s attached and eventually causes failure.
Galvanic action is a chemical reaction caused when two dissimilar metals, like copper and galvanized steel, are installed next to one another. When an electrolyte, like water, is introduced, the metals will corrode faster.
Slate is popular because it’s durable, fireproof, and looks amazing. It comes in a wide variety of colors making it an effective design choice for many architectural styles. Soft slate is subject to erosion due to airborne and rainwater chemicals which cause wear at the nail holes, de-lamination, or breakage. In colder climates, slate is susceptible to breakage by ice.
Wood shingles were used throughout the country in all periods of building history. Wood had different shingle sizes, styles, and woods used depending on the region. For example, in New England, white pine was common, while in the South, cypress and oak were often the woods of choice. In urban areas, wood roofs were often replaced with more fire-resistant materials. Wood has a limited lifespan due to normal organic decay, wear, and tear. They also erode due to exposure to rain and ultraviolet light.
While these materials are typically used on historic roofs, some local building codes may allow alternative replacement materials. For example, asphalt shingles or ceramic tiles that look like wood, slate, or vintage shakes are good replacements. If natural wood is preferred, fire-retardant wood shingles are available; however, they can be brittle. There are also less expensive variations of sheet metal available like lead-coated copper, teme-coated steel, and copper coated steel to replace teme plate, lead, or copper roofing. Ask your local contractor for information on your local building codes.
Looking Beyond Material Failure
Once the condition of the roofing material is determined, the related support systems of the roof should be examined. In a historic roof replacement or repair, these systems often contribute to the deterioration of the roof. If they’re not addressed when replacing the roof, it can significantly shorten the lifespan of the roof material.
At Steven’s Roofing, we understand historic roof replacement. Doing research to find out more about the history of the roof and original plans can be helpful. It pays to know what type of service has been carried out and what types of events the roof may have already been through.
If you live in a historic home in the Norfolk, VA area, give the experts at Steven’s Roofing a call. For over 70 years, 3 generations of the Stevens family have been providing quality historic restoration services in the greater Norfolk area.