ROOFMASTERS.inc FREQUENTLY ASKED QUESTIONS
WHAT WILL SHINGLES LOOK LIKE AS THEY AGE?
You may be asking yourself, "What can I expect a roof to look like as this aging process takes place?" One or more of the
following conditions may occur over time.
Curling
As the asphalt hardens over time, the granules which were once securely embedded begin to break away. Occasionally you
may have seen the colored granules in gutters. Also, as this hardening advances, the asphalt layers begin to shrink. Of
course, all this is occurring at a microscopic level and is no noticeable on a daily basis. As the asphalt layer shrinks, it is
being countered by the shingle reinforcement, which resists shrinking. We now have a situation in which the top and bottom
coatings are shrinking and the reinforcement is remaining stable. As a result, the edges of the shingle may begin to curl.
Surface Cracking
Another manifestation of the normal aging process may be the development of surface cracks. For example, as the
flexibilizing oils of the asphalt are depleted due to heat, the shingle becomes more brittle, to the point where surface
cracking may appear. The stresses created by thermal shock and the movement of the roof deck also increase the
likelihood of surface cracking.
Blistering
During the course of natural weathering, small bubble-like raised areas known as blisters may appear on the surface of
the shingles. The blisters may be small and pea-sized, or as large as a quarter. The blisters may be open, exposing the
asphalt, or closed. Blisters frequently result when minimum ventilation requirements are not met.
Staining
Finally, over a period of time, shingles may develop dark brown or black streaks that are sometimes mistaken for soot,
dirt, moss or tree droppings. In actuality, this discoloration may be caused by algae growth. Although most roofing systems
are susceptible to algae discoloration, it is most readily visible on white or light-colored shingles.
DO LIGHT-COLORED SHINGLES LAST LONGER THAN DARK SHINGLES?
On structures with attics and proper ventilation, light and dark shingles should last about the same amount of time. Without
proper ventilation, it is possible that the darker shingles might have a shorter life as a result of their tendency to reach
higher temperatures due to increased absorption of solar energy. The hotter deck may bake the shingles, causing the
asphalt to become brittle and the shingles to fail prematurely.
IS VENTILATION REALLY THAT IMPORTANT?
Deck movement and deterioration are commonly the results of poor ventilation. In the summer, too much heat buildup due
to a poorly ventilated "flat ceiling" attic can cause the shingles to deteriorate prematurely. In the winter, deck-related
problems are often due to condensation forming on the deck underside, which is also a result of poor ventilation. It is
important to understand that shingles failing before their time due to inadequate ventilation will not be protected by the
manufacturer's warranty.
WHY IS SHINGLE UNDERLAYMENT REQUIRED?
When we look at the performance of the roof system as a whole, underlayment has a legitimate role to play. Underlayment is
considered to be an important component in the UL (Underwriters Laboratory Inc) fire resistance classification. It can provide
backup protection in case of a shingle blow-off, and during the installation of shingles it can keep the unshingled decking dry.
WHAT IS SHINGLE UNDERLAYMENT?
On slopes below 4/12, down to 2/12, the risk of leaks is great, caused by phenomena like wind-driven rain and capillary
action that can make water flow uphill, or by the backup of water behind ice dams. To reduce this risk, a redundant
systems called "shingle underlayment" is applied beneath the shingles. Shingle underlayment, also known as tar paper and
roofing felt, is a roll product applied over the roof deck before the shingles are installed. The term "underlayment"
is not to be confused with the flooring sub-base. The OSB on a roof deck is not shingle underlayment; it is properly termed
roof sheathing and must be rated by the American Plywood Association as such. On the other hand, not all shingle
underlayment is the same. There are two critically different grades:water-resistant and waterproof. Water-resistant
underlayment was invented to keep the roof decking dry until shingles could be applied. Applying this underlayment is
called "drying-in the roof." It was also useful as a separation sheet between the roof sheathing boards and the asphalt
shingles before OSB and plywood sheets were used as roof decking. This separation was important because direct contact
with resin pockets in the pine planks caused the asphalt to degrade prematurely. Intact water-resistant underlayment sheds
most of the water that falls on it, but its water resistance is temporary. As the sun degrades the exposed asphalt the material
begins to dry out, absorb more moisture, lose its strength, and eventually tear. The less asphalt used to saturate the
underlayment sheet during manufacture, the shorter its life. Since asphalt is the most expensive component of shingle
underlayment, lower-priced materials have less asphalt and a shorter life when exposed to the sun, and are also subject to
severe wrinkling when wet or even just damp. Water-resistant shingle underlayment is not warranted by the manufacturer.
It is an expendable material because much of its water resistance is destroyed during the installation of shingles by
driving hundreds of nails through it. Until recently, only two grades of water-resistant underlayment have been available:
Number 15 (standard) and Number 30 (heavy-duty). In recent years new categories have appeared known as premium and
high-performance shingle underlayment. These materials are less likely to wrinkle when dampened. Waterproof underlayment
is an entirely different product that's used in locations such as eaves and valleys that are most likely to leak under extreme
conditions such as high winds, heavy rains and ice dams. This material is known as WSU (waterproofing shingle
underlayment).
On low slopes where the risk is water running uphill, or in valleys where blockage from storm debris or ice dams can cause
trouble, WSU is reliable insurance against leaks when used according to the manufacturer's instructions. In all cases the
product must be applied to a clean, dry roof deck.
WHAT IS FLASHING AND WHY IS IT REQUIRED?
The roof deck is most vulnerable to leaks where it meets a vertical wall, at penetration sites such as a soil pipe or
chimney, or at changes in slope such as at a valley, saddle, mansard, hip, or ridge. This vulnerability is due to:
1. Deferential movements (e.g., the roof deck moves but the chimney does not).
2. An accumulation of turbulent water (e.g., in valleys and on the high side of chimneys).
3. An accumulation of melting snow or ice (e.g., in valleys and on the high side of chimneys).
4. Breaks in overlapped shingles (e.g., at hips and ridges).
Flashing is installed at these locations to bridge adjoining structures and prevent water penetration. Flashing materials
include sheet metal; cements, caulks, and sealants; and flexible sheets such as waterproofing shingle underlayment.
At hips and ridges the cap shingles, not normally called flashing, serve the same function. Leaving out ice dam backups
and catastrophic damage from severe storms, old age, or gross manufacturing defects, leaks are most likely to originate at a
flashing that has failed or was improperly installed.
WHAT ARE SHINGLE TYPES?
Laminated shingles: There are many different brands and sizes of laminated shingles.
Mid-Weight Dimensional Shingles: These shingles offer a more interesting appearance on the roof than three-tab shingles.
Typically they weigh 235-265 lbs./sq. Shadow lines and contrasting color blends are common.
Heavyweight Dimensional Shingles: The heavyweights are sometimes called architectural shingles.
Typically they weigh 265-350 lbs./sq. Shadow lines and contrasting color blends give the appearance of a thick shingle.
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