According to a recent national data from the American Society of Home Inspectors, the most common problem area uncovered by inspectors is roofing. Roof problems are 3 times more prevalent on inspection reports than the second most frequent problem, electrical.
The most common type of roof in this area is an asphalt composition roof, called comp for short. Until the early 80′s, they carried a 15 year manufacturer’s warranty, though currently installed fiberglass shingles have a 20 year warranty. You may also hear of roofs referred to as a 175# or 225# roof. These figures refer to the weight of shingles required to cover 100 sq. ft. of roof area, (a “square”).
To some extent, the weight of a shingle is related to quality, i.e. the heavier the shingle, purportedly better the quality. With the advent of lightweight fiberglass shingles, the weight of a square roofing materials is less of a measure of the quality than it was with the old style asphalt shingles.
The asphalt composition roof had an organic felt material as a base whereas, the fiberglass composition roof has fiberglass as its base. The use of the fiberglass mat causes the roofing material to have a longer life.
Manufacturer’s warranties are generally limited, pro rata warranties that apply only on to the shingles themselves, not the installation labor.
By a pro rata warranty, I mean that if you purchase a new roof and the shingles fail after 14 years, you are entitled to receive 6/20ths of the original purchase price of the shingles in satisfaction of the warranty. Some warranties are front-end loaded, meaning if the shingles fail during the first few years of service, you will receive a higher percentage of the purchase price in satisfaction of the warranty as opposed to a failure near the end of the warranty period.
In most cases the warranty covers only the original purchaser of the shingles and it is not transferable to any subsequent owner. The manufacturer’s warranty is usually found on the paper wrapping around each bundle of shingles and the supplier of the shingles should furnish the purchaser with a warranty document indicating the date of the sale and installation of the product. Any reputable roofer will furnish you with copies of the manufacturer’s warranty.
When installing a new roof on property as a condition of sale, make sure the warranty is transferable to the purchaser or the warranty is registered in the name of the purchaser of the property. Any warranty covering labor is made by the roofer installing the shingles and should cover not only the installation of shingles, but all flashing, decking, valleys and other work done in connection with installation of the roof. Also, most manufacturer’s warranties are voided if it can be shown the roof was improperly installed. This tends to happen more frequently than anyone would like to admit. It is another reason for hiring a reputable, bonded roofer to do the installation.
The sun in Texas is the main enemy of shingles and causes them to deteriorate more rapidly than up North.
The Building Code states that it is acceptable to have up to 2 layers of roofing on a house though no good roofer will do an “overlay”.
The actual number of layers that is acceptable is a function of the type of framing the roof has. A roof supported by 2″x 4″ rafters can carry less weight than those supported by trusses or 2″x 6″ rafters. You are inviting a sagging roof if you put more than one layer of shingles on the former. In many older homes that have no ridge board (the board running between the rafters at the peak of the roof) and little or no rafter bracing, the framing will not support 2 layers of shingles without sagging
The cost of roofing, though not outrageous, can easily cramp your social life. Replacing an existing roof commonly runs from $135 to $150 per square (100 square feet). This assumes that you choose the normal lightweight composition shingles. Longer lasting shingles or roofs with steep pitches & numerous “valleys” will cost more.
Another item to remember, not all roof leaks are caused by failure of the shingles. Most often leaks are the result of improperly installed or failed metal flashing around vents, chimneys, or in valleys. In other instances, the leak may be caused by the failure of the decking, trusses or rafters which causes the shingles to buckle or separate. Shifting of the foundation can put sufficient stress on the roof to cause leaks.
As a final comment, let me just say that roofing, contrary to popular opinion, is a complex subject as there are scores of different acceptable materials and installation methods. Regardless of the materials, the roof is only good as the roofer who installs it. If any shortcuts are taken, you can look forward to “rain drops falling on your head” at any time in the future; usually at midnight, on weekends or holidays.