The Housechick Blog

Brought to you by Dave Brownell of Second Opinion Home Inspections, Tucson Home Inspector Extraordinaire.  Thanks Dave!

Tucson homes have a wide variety of styles and roof types.  One style of roof not commonly seen in other areas of the country are flat roofs.  Flat roofs, like all roofing systems, have benefits and drawbacks.  Since a roof is a major component of a house, it is important to understand your roofing system: how it works, what to watch out for, and how to maintain it.

Dave Says:

Like all roofing systems, flat roofs are designed with the purpose of protecting the home structure from the intrusion of water. Though called flat, they are not really totally flat. Flat roofs are designed with some amount of slope from one edge to the opposite edge in order for water to run off. The slope can be as little as 1 inch per 12 feet, usually not more than 2 inches per 12 feet. Roofs with greater slopes that look like flat roofs are called shed roofs. Both are very similar in design, construction and maintenance.

Types of Coverings

These roofs can have several types of coverings: Rolled Asphalt, Built-up-painted (also called built-up-reflect), Foam, and Membrane.

Rolled asphalt roofing material is similar to asphalt shingles, it has granules just like shingles, except it comes in long rolls about 3 feet wide and is laid down with each subsequent row overlapping the previous with sealer between the lap. Rolled asphalt systems can be found on entire homes, but is usually found only on addition and patio roofs. Typical life expectancy is approximately 10 years.

Built up - painted, probably the most common flat roof covering, is a system where each layer of a 3 foot wide roll of heavy roofing tar paper is overlapped by at least one half on each course and “hot mopped” or covered with a hot roofing tar between each layer, totally sealing everything in the tar. This is referred to as the underlayment. Then the entire roof is painted with a special reflective paint, usually white or silver.  Sometimes a desert color may be required by an HOA (home owners association). Typical life expectancy is approximately 15-20 years for the underlayment and 3-5 on the painted roof coating.

Foam roofs are usually installed over a built up roofing system. This is a foam product that is blown onto all roof surfaces and is approximately 1-2 inches thick. It is generally painted with the same roof coating as the built up roof. Care and maintenance is similar to that of a built up roof.

Membrane roofs are a vinyl or rubberized product that is stretched across the entire roof area and folded over the edges to provide a seamless roof, with the exception of where plumbing vents and the like will protrude through. Some more modern versions of this type may be used on very large roofs and may be seamed at several areas across the roof. Typical life expectancy is approximately 15-25 years. Higher claims are being made regarding the newer style, however, not enough time has passed to validate these claims.

Common Problems

Because of the low slope of a flat roof, over time many of the roof surfaces begin to sag and create low spots on the roof where water can settle and can’t run off. This is called ponding. These areas will be the source of most of your maintenance.

To the left is a picture, an example of what ponding looks like on a built up painted roof.

Rolled Asphalt roofs can loose their granules over time. From expansion and contraction, the material itself may buckle or wrinkle causing ridges that can crack and eventually leak. Also, if installed with roofing nails around the edges, the nails can work loose or “pop,” causing a hole for water to intrude.  To the right is a picture of nail pops on the edge of a roof.

The painted roof coatings on built up or foam roofs have a limited life expectancy, typically 3-5 years.  If these roofs are not maintained, damage may be caused to the underlayment of the roof. Besides ponding, blistering and cracking are also to be expected. Cracking can occur on the painted roof surface and expose the black underlayment beneath and promote premature deterioration. Blistering will appear as bubbles on the surface and have a soft airy feel to them, they may even pop when you step on them. As much fun as that may sound, unless you are prepared to reseal them it is best to leave them alone.

Membrane roofs can be affected by the suns ultraviolet rays and can eventually deteriorate and even shrink. They can also get punctured by foreign objects which would be a source for water intrusion.

Maintenance and Care

Rolled Asphalt: Periodically look across the roofing surface for the formation of the buckles or wrinkles and monitor them. Before a crack is visible at the ridge of the wrinkle it should be repaired.  Also, any “popped” nail heads should be sealed and reset.  To the left is a picture of a wrinkle in a rolled asphalt roof.

Built up – painted and Foam Roofs: A painted roof should be inspected annually, especially if areas of ponding are visible. Any loose, cracked paint coating should be removed and repainted as regular maintenance until it is time to recoat the entire roof. Blisters, which appear as a bubble, should be cut out, removed, and the area recoated.

Membrane: Little maintenance is required on membrane roofs, however regular inspections are recommended in case of damage.

All Roofs:  All the systems above should include the inspection of the flashing, which is where the plumbing vents and air condition ducts that come up through the roof surface are sealed. The sealer, usually roof tar, should be inspected for shrinkage, cracking, and peeling. Older, loose material can be cut away and new tar smeared all around the area. Let dry several days then paint. Newer homes will use a rubber flashing material around round plumbing vent pipes and these too should be inspected for dry cracking and shrinking. These should be painted to protect the rubber from the UV rays. If cracked they can be sealed with roofing tar and later painted.