Quality roofers install double flashing on tile roofs
Q. My tile roof is leaking in an unusual way. No moisture is getting into the house, but I've seen water running from beneath the tiles at the edges of the roof. When I bought the house, my home inspector said water was likely to leak around the vent pipes. He advised repairs, but I didn't think much of it at the time. Since then, I've noticed that the metal fittings around the vent pipes are installed differently than on my neighbor's roof. I asked a roofing contractor about this, and he said my home is older and the roof was installed according to older standards. He said repairs are not necessary if water is not getting into the house. Does this sound acceptable to you?
A. The sheet metal fittings around the vent pipes are called flashing. The purpose of flashing is to promote water runoff over the surface of the roof, rather than under the tiles. The old method for flashing the pipes was called single flashing. With that method, water was allowed to drain under the tiles, unless mortar was packed around the pipes. This was considered to be an acceptable roofing method because the waterproof membrane under the tiles was expected to prevent leakage into the building. Unfortunately, this method was not always reliable because leaking could occur where nails penetrated the waterproof membrane. Furthermore, the membrane could become deteriorated with age, which would also enabled leakage.
During the past 10 to 20 years, double-flashing has become the standard of the industry, not because of changes in the building code, but because tile manufacturers have upgraded their installation specifications and because the roofing industry has recognized the need for change. Double-flashing, as the name implies, involves two separate flashings on each pipe: one beneath the tiles and one that overlaps the tiles to promote drainage over the tiles rather than beneath them.
Unfortunately, there are still some roofing contractors who use the old, single-flashing method, but double-flashing is clearly the more effective and reliable method of installation. It may not be a legal requirement, but it is the only sensible way to flash a tile roof.
Q. The house I'm buying has an intact roof, but my home inspector said it is an obstacle course of loose TV cables. In fact, he tripped on one of these wires and fortunately did not fall off the roof. Aren't there any rules affecting the way TV cable companies install their lines?
A. Regulations governing the installation of low-voltage utility wires prohibit the laying of unsecured lines on the surface of a roof. Unfortunately, some of the people who install TV cables fail to consider the trip hazards they create when installing their lines, and since the need to walk on a roof may not occur until years after the cables are installed, cable companies are unlikely to receive many complaints about this careless practice. However, now might be a good time to give them a call.
• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.
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