Thanksgiving is always the 4th Thursday of November, kudos to President Franklin D. Roosevelt and Congress back in 1941. And, yes, on this day, we gather with family and friends and give thanks for all our blessings (and eat turkey and pie and watch football!). But did you know that National Roof Over Your Head Day is December 3, 2014? Most of us take for granted the fact that we have shelter readily available when things turn unpleasant outside. This unofficial holiday draws attention to those less fortunate and reminds us to appreciate the basics. So how often do you think about that little luxury overhead….your roof? If you are like most people, probably not until something goes wrong.
A roof can impart much of the architectural character of an historic home. Picture Queen Anne turrets, Georgian hipped roofs, Mansard roofs, the sloping roof line of a Bungalow. However, regardless of its age, size, or design, a weather-tight roof is basic to the preservation of a structure. A poor roof will eventually lead to the overall disintegration of any building. If you have roof troubles, it is best to have a professional roofing contractor pinpoint the problem. It could involve failure of surface materials or of the support system–or both. Here are some common problems that can develop with your historic surface materials (those being wood, metal, tile, and slate):
Some historic roofing materials have limited life expectancies because of normal decay and simple wear. For example, although some types of wood are more hardy than others, all wood shingles will eventually erode due to exposure to the elements and ultraviolet rays. If moisture gets in to the grain of the wood, it will deteriorate, while prolonged moisture on or in the wood allows moss and other yummies to grow causing more rot.
Commonly-used sheet metals used on historic buildings include lead, copper, zinc, tin plate, and galvanized iron. These metals chemically deteriorate due to airborne pollutants. Iron, in particular, will rust. Luckily, this can be avoided by use of tin plating or galvanizing. However–just like the rust-proofing on your once-new car–this protection lasts only as long as the coating remains intact. Once the plating is worn or damaged, exposed iron will rust. Therefore, it is a good idea to undercoat any iron-based roofing material and keep the surface well-painted to prevent corrosion (be Anti Deferred Maintenance!).
Another problem that can afflict metal roofing materials is fatigue. Both wear and metal failure can occur at the sheathing joints as a result of the metal’s alternating movement to thermal changes. Lead eventually tears due to gravitational stress, causing it to move down the roof slope.
Roof shingles made of tile weather well but there is always the possibility of cracking or breaking if hit–such as by tree branches–or if improperly walked on. The quality of the tiles can also be an issue. Low quality tiles that were not fired correctly when made, or tile containing impurities will craze and spall as a result of normal freeze/thaw cycles (an example of this is when your outdoor ceramic planter splits when the temperature goes from 30 to 60 degrees F, as it just did here in Cincinnati last week).
Slate shingles, although also very durable, can also vary in quality. Some slate is hard and tough and not very brittle. Soft slate can erode and be affected by pollutants in the air and rainwater. Slate will wear at the nail holes, delaminate, or simply break. Winter can be very hard on slate due to ice or ice dams. Slate does not really care for being walked on…
Cincinnati Historic Homes wishes you a very happy Thanksgiving and National Roof Over Your Head Day. Don’t forget to be thankful for that historic roof over your head and think of how many Thanksgiving dinners it has sheltered over the years and decades. We hope it presides over many more to come!