Asphalt Shigle Roof
A roof is one of the most expensive components of a home. Hundreds of different materials have been used as roofing material from sticks to plastic, and grass to glass. When you are looking for a home you need to know what type of roofing material is installed, if it was installed correctly, and the current condition. A thorough home inspection will include a detailed evaluation of the roof. A roof in poor condition can be a deal breaker, so here are some things to look for that can give you a heads-up about the condition of a roof.
The majority of the houses we inspect range in age from the 1950's to new. The most common roof material we see in San Diego is the three-tab composite asphalt shingle roof. It is made of oil-impregnated fiberglass material, with an aggregate (which looks like kitty litter) pressed into the surface. The aggregate adds color, but its primary purpose is to protect the shingles from UV exposure. Once the aggregate is worn, the shingle deteriorates rather quickly. The majority of asphalt shingles have a life expectancy of 20 or 30 years.
Before making an offer on a house, take a close look at the roof. If you see worn areas, this indicates that the shingles are near the end of their life. You can also do some simple math to estimate the age of the roof. If you are looking at a house built in 1970, the house is 40 years old. Assuming that the house originally had a 20-year asphalt roof, it was most likely replaced in the early 1990's. That means that the current 20-year roof is near the end of its 20 year expected life.
Look around the perimeter of the house for evidence that the aggregate is washing off of the roof. If you see piles of gritty material which is the same color as the roof, you'll know that the roof is deteriorating.
The other most common roof type in San Diego is the tile roof. Authentic Spanish tile roofs are made from baked clay, and the color is solid all the way through. These tiles will last a long time; 50 – 100 years if properly maintained.
A less expensive, but very durable material is the concrete tile. These tiles are more uniform, and are color covered concrete. These come in a variety of shapes and colors. Tiles can be flat, or curved to emulate Spanish tiles. These tiles should last 50 years, though some of these tiles were poorly made and will not last that long. You will notice that some tiles, which should be glazed, are now dull and often have moss or dark staining on them. Some roof contractors will recommend that you replace these tiles.
Prior to the 1990's, many tile roofs were poorly installed without the metal flashings now common on tile roofs. On the older tile roofs, the bottom edge of the lower row of tiles was held up by a small board commonly called a shadow board, so that the slope of the tile was consistent with those at the upper rows. (On the upper rows, each tile rests on the top edge of the tile below it.) Without a shadow board, the bottom row of tiles lay at an different angle than the restinder of the roof.
The tar paper was draped over the shadow board. Over time, the paper sagged causing water to "pond". The standing water damages the paper underlayment, which can cause damage to the wood under the paper, and the fascia. To make matters worse, the open end of arched tiles allows the sun to shine in on the paper. The UV rays caused the paper to dry out and shrink. Once the paper deteriorates, water then pools behind the shadow board causing dry rot.
Newer tile roofs installed after the mid-1990's were installed with a metal flashing at the bottom edge of the roof. This flashing serves several purposes, it holds the bottom row of tiles at the correct angle, it encloses the open end of arched tiles, and it acts as a drip edge to direct water away from the fascia board.
There is another important reason to "close" the ends of the tile. Wind driven fires provided devastating even for houses with tile roofs. That is because embers were blown up into the roof through the open ends of the tile. There the embers start roof fires which are very difficult to extinguish. This flashing is often referred to as "bird stop" for its ability to keep birds from nesting under the tiles.
If you are purchasing a house that is 20 years old or more, take the time to look at the roof. You could save yourself a lot of heartache later.
About the author: Philippe Heller is the president of The San Diego Real Estate Inspection Company in San Diego, CA. www.sdinspections.com