Many types of roofing permit the application of a coating for a variety of reasons, such as
increasing solar reflectivity, resisting biological growth, improving impact resistance, or
increasing roof life. However, ARMA strongly advises against the application of any type of
field-applied coating over installed asphalt shingles.
There are many types and formulations of roof coatings, so it is always important to consult the
shingle manufacturer before proceeding with any type of coating. Many asphalt shingle
manufacturers specifically do not recommend field coating of their shingles. Additionally, state
or local building codes may prohibit this practice, as the field-applied coatings may negatively
impact the performance characteristics (including the fire classification, algae resistance,
impact resistance, etc.) of the roof assembly.
Some of the problems reported after asphalt shingle roofs have been field coated include
shrinking of the coating, which may result in unsightly curling and/or cupping of the shingles or
loosening of the granule surfacing of the asphalt shingles. In addition, non-permeable roof
coatings may create a vapor-retarding layer by sealing the voids around and between the
shingles. If this occurs, it may contribute to moisture accumulation within the roofing system.
It has been suggested by some that the use of field-applied coatings over existing asphalt
shingles will produce overriding benefits to the homeowner, such as longer roof life, energy-use
reduction, or remediation of small roof leaks. There is limited available documentation showing
the extent to which the field coating of asphalt shingles provides any of these benefits, but the
risks and concerns mentioned above remain very real. Further, many coatings need regular
maintenance reapplications to provide a consistent appearance.
In summary, the application of a coating may be detrimental to asphalt shingles. Be sure to:
• Check with the asphalt shingle manufacturer before determining a specific roof
coating.
• Check with the local building and zoning department and, if appropriate, your
homeowner’s association to determine whether this application is allowed.
The Asphalt Roofing Manufacturers Association (ARMA) has established the following
recommendations for applying asphalt shingles and/or asphalt-based underlayment directly
over insulation, insulated roof decks, and radiant barriers.
Asphalt Shingle and/or Asphalt-based Underlayment Application Directly over Insulation
Applying shingles and/or asphalt-based underlayment directly over insulation is not
recommended for several reasons.
• Asphalt shingles and/or asphalt-based underlayments are designed for attachment to
deck surfaces such as plywood and oriented strand board or other surfaces acceptable
to the asphalt shingle or underlayment manufacturer.
• Continuous free-flow ventilation is impossible to achieve when applying shingles and
asphalt-based underlayment directly over insulation. Heat build-up, a typical result of
inadequate ventilation, may accelerate weathering and reduce the anticipated life of
the products.
• Asphalt shingles and/or asphalt-based underlayment may be damaged or punctured
when nailed onto a non-rigid surface such as roofing insulation.
• Insulation does not have adequate nail-holding ability. Consequently, shingle damage
and/or blow-off may occur if shingles are attached to insulation. Wind classification of
the installed roofing system may be affected.
The fire classification of asphalt roofing products may be adversely affected when applied
directly over insulation. Individual asphalt shingle and/or asphalt-based underlayment
manufacturers should be consulted to determine the effects on such classifications. Fire
classification installed roofing system may be affected.
Asphalt Shingle and/or Asphalt-based Underlayment Application Directly over Insulated Roof
Decks
Applying asphalt shingles and/or asphalt-based underlayment to insulated roof decks is not
recommended unless the following factors are considered.
• Direct installation over insulated roof decks is not recommended unless an adequate
continuous ventilation space, free of obstructions, is provided between the top of the
insulating material and the underside of an acceptable roof sheathing, Proper
ventilation must be provided to dissipate heat and humidity build-up under the roof sheathing. More information on this can be found in ARMA’s technical bulletin,
Ventilation and Moisture Control for Residential Roofing. Factors influencing the
minimum ventilation requirement include type of construction, roof pitch/run,
temperature, humidity, etc. Consult the deck manufacturer, deck system designer, and
asphalt shingle/underlayment manufacturer for specific requirements.
• Asphalt shingles and/or asphalt-based underlayment should only be fastened to deck
surfaces such as plywood and oriented strand board or other surfaces acceptable to the
asphalt shingle manufacturer.
• Application of asphalt shingles and/or asphalt-based underlayment directly over
insulated deck systems without providing adequate ventilation may affect the asphalt
shingle and/or asphalt-based underlayment manufacturers’ product warranties. Consult
individual product manufacturers for details and refer to local building codes.
Asphalt Shingle and/or Asphalt-based Underlayment Application over Deck Systems
Containing Radiant Barriers
Applying asphalt shingles and/or asphalt-based underlayment over deck systems containing
radiant barriers is at times acceptable, but several considerations should be noted.
• Radiant barrier sheets that are fastened between or beneath the roof rafters should
have proper ventilation between the radiant barrier and the decking so heat and
humidity build-up can be dissipated.
• Radiant barriers require a minimum 1-inch air space between the metallic surface and
the next nearest surface. Otherwise, thermal conduction will override the reduction in
radiant heat transfer. See the US Department of Energy’s bulletin on Radiant Barriers
for more information (found here).
• Radiant barriers installed directly beneath and in contact with the roof deck sheathing
may interfere with proper deck ventilation. The asphalt shingle and/or asphalt-based
underlayment manufacturers’ product warranties may be affected, so consult individual
manufacturers for details. Refer to local building codes for specific project requirements
that may apply.
Ventilation Considerations
Most vent system manufacturers recommend a soffit/ridge (inlet/outlet) venting ratio of
between 50 and 60 percent. An air space of 3/4-inch (19 mm) is suggested as a minimum
ventilation space; a 1.5-inch (38 mm) or wider space is preferred. Factors influencing this
measurement include type of construction, roof pitch/run, temperature, humidity, etc. Larger
roof expanses, such as those on commercial buildings, may require a much larger air space to
move heat and moisture from the system because of their longer run. Adequate intake airflow
must also be provided for proper ventilation dynamics. Consult the deck manufacturer, deck system designer, and asphalt shingle/underlayment manufacturer, as well as local building
codes, for specific requirements. Some methods for creating a continuous air space for proper
ventilation are shown in Figures A, B and C.
When the time comes to reroof an existing asphalt shingle roof, a decision must be made whether to remove the old shingles or
apply new shingles directly over the existing layer. Most building codes define the options as follows:
Reroofing: The process of recovering or replacing an existing roof covering.
Roof Recover: The process of installing an additional roof covering over a prepared existing roof covering without
removing the existing roof covering.
Roof Replacement: The process of removing the existing roof covering, repairing any damaged substrate and installing
a new roof covering.
In some cases, local building codes will limit the available options—most do not allow more than two roof coverings on a
building. However, there is no easy, universal answer if only one roof is in place. Although in many cases it is not necessary to
tear off old shingles before installing new shingles, some roofing professionals will insist on replacement because it ensures that
a completely new roofing system is installed.
Although each roof must be evaluated individually, general guidelines can help make an informed decision whether to replace or
recover an existing asphalt shingle roof.
If a roof has only one layer of shingles that lay flat and the decking is in good condition, a tear-off may not be needed.
Not only will the existing layer provide a secondary back-up roof for the new shingles, but it will also save the cost and
inconvenience of removing and disposing or recycling the old shingles.
Before making a final decision to tear off or recover, check that local building codes are being followed.
Adequate roof ventilation should be provided (See ARMA Technical Bulletin, “Ventilation and Moisture Control for
Residential Roofing” for additional details and information).
The existing shingles will probably have to be removed if:
An inspection of the roof deck reveals rotted or warped wood or large gaps between the deck boards. Any rotten or
damaged boards must be replaced before applying new shingles. [Note: for best roof performance, consider re-decking
“board” roof decks with a layer of APA (The Engineered Wood Association) Grade ½” plywood before installing new
shingles.]
There are more than two layers of existing shingles on the roof. Note that the local building codes may require removal
of more than one layer.
The roof structure shows signs of sagging across the ridge or truss lines. If the roof does not look straight and feel solid,
have the structure inspected by a licensed structural engineer to check for structural defects.
The condition of the existing shingles is so uneven and distorted that it would not be practical to flatten all raised areas
enough for the new roof to lay flat.
Many factors may play into whether a roof can be recovered or replaced, so it is important to discuss the options with your
roofing professional. Your decision can impact the curb appeal of your home and the performance of your roof.
Asphalt shingles have been used successfully in cold climates for over one hundred years.
Improved application efficiency, and more importantly, enhanced long-term shingle
performance, can be achieved by following the cold weather application recommendations
outlined below:
• Be sure to follow the manufacturer’s installation instructions carefully, as most building
codes require, including manufacturer recommendations about cold temperature
application and proper storage and handling of accessory components used in the
installation of an asphalt shingle roofing system.
• Be very careful when working on sloped roofs. In winter applications, there may be
nearly invisible ice or frost build-up on the roof or deck surface, which can make work
extremely hazardous. It is advisable to wait until the roof surface is free of ice and frost
for safer shingle roof application.
• Use caution when handling bundles of shingles and individual shingles in cold weather
as they may crack, or in severe cases, break apart. Choose an installation temperature
where the shingles are sufficiently flexible to facilitate installation. As with most
materials, asphalt shingles tend to become less flexible as temperature decreases. Refer
to manufacturer instructions for specific directions related to cold weather installation
temperature. Note that when cold, shingle bundles will tend to keep the shape of the
surface upon which they are stacked. When nailing, make sure the shingles are flat;
otherwise, the nail may break through the shingle surface during installation. Avoid
bending, throwing, or dropping bundles of shingles in cold weather. For best results,
store shingles indoors to keep them warm prior to application.
• Use extra care (including warming of shingles) in applications where lifting or bending
the shingle is required, such as racking applications, hip and ridge shingles, or at valleys.
Lifting or bending may cause the shingles to crack or break during or after installation.
• Most asphalt shingles include thermally activated asphalt sealant, which bonds the
shingles together after they are applied to the roof. Sealing time will vary depending on
the slope of the roof, its orientation, and the amount of sun/heat exposure that the
shingles receive. To provide improved protection from wind blow-off in very cold
weather, asphalt shingles can be hand-sealed with an approved asphalt roofing cement
or other adhesive acceptable to the shingle manufacturer and in accordance with their installation requirements.
• Consider the use of open metal valleys in cold weather. Woven and closed cut valleys
require shingles to be bent, which may result in shingle damage.
Additional Considerations
• When re-roofing over an existing roof in cold weather, take extra care to ensure that the
roof surface is smooth and flat. If shingles are affixed to an uneven surface in cold
weather, that uneven appearance may be “locked in.” Even with the return to warmer
weather, the shingles may not be able to completely relax to a smooth looking finished
roof.
• Ensure that the attic space is adequately ventilated.1
• Install polymer modified, self-adhering underlayment as ice dam protection in regions
susceptible to ice damming. Self-adhering underlayment provide protection against
damage from water backup from ice dams that can occur at the eaves of the roof.2
Asphalt saturated felt may be used as an alternative ice dam protection when applied
per the manufacturer’s application instructions and the requirements of the building
code.
• If roof maintenance or inspection is required in cold weather, take special care when
walking on shingles. Shingles applied to an uneven surface, or that are slightly curved or
buckled, are very susceptible to breakage underfoot in frigid weather. For some
sealants, the bond between courses becomes less flexible in cold weather and roof
traffic may break the sealant bond. In such cases, it may be necessary to hand-seal these
shingles.
Certain North American regions receive very high snowfall amounts, requiring snow and ice
removal from the roof. Extreme caution must be taken when removing snow from the roof so
that the shingles are not damaged by shovels, scrapers, or foot traffic.
Built-Up Roofing (BUR) membranes have been in use in North America for more than 100 years. BUR systems
predominately consist of alternating layers of asphalt (bitumen) and fiberglass ply felts that create a very durable
water resistant membrane. The number of plies within a cross section of the system will denote the type of system.
“Three or four plies with a flood coat of asphalt and gravel” is a common phrase used to describe a BUR system.
Built-Up Roofing Asphalt (BURA) is manufactured to meet various technical specifications. In the United States, BURA
should meet the current version of ASTM D312, and in Canada, the current CSA 123.4 standard. The asphalt
producer should provide certification of the asphalt provided upon request. ASTM D312 defines four types of roofing
BURA (Types I, II, III, and IV); considerations affecting the proper type of asphalt for a particular job include roof
slope, environmental conditions, local roofing codes and practices, and the type of construction on which the roof
membrane will be applied. Consult the roofing manufacturer and/or specifier regarding proper asphalt type.
Temperature control is a critical objective on every hot asphalt roofing project. Excessive heating can cause
degradation of the asphalt, significantly increase worker exposure to fumes, and create kettle fire and explosion
hazards. Asphalt should always be used at the lowest practicable temperature given the specific application.
The proper temperature for BURA application is the equiviscous temperature (EVT), plus or minus 25°F. On a job the
EVT is measured in the mop cart, bucket, or mechanical spreader just prior to application to the substrate. ASTM
D312 requires lot-specific EVTs for both mop and mechanical spreader application to be indicated on each carton of
asphalt or bill of lading. Application temperature at the point of ply felt contact may also be impacted by ambient
conditions but should not deviate from the EVT by more than 25°F. ASTM D312 specifies maximum EVTs for Type III
and IV BURA to help prevent overheating. In the case of modified bitumen systems applied using hot asphalt, consult
manufacturer recommendations on proper application temperatures.
ASTM D312 specifies a maximum kettle temperature of 550°F (288°C). Kettle temperatures should be kept as far
below this maximum temperature as possible, while maintaining a temperature within the EVT range at the point of
application. Some recommendations to help minimize heat loss between the kettle and the roof include the
following:
Recommendations
Regarding Built-Up
Roofing Asphalt
2 of 2 Amember service provided by the Asphalt Roofing Manufacturers Association Revised May 2016
Minimize the distance between the kettle or tanker and the point of application on the roof
Use insulated kettles with capacities appropriate to the job and with high pumping rates to deliver the
hot material as quickly as possible
Insulate the hot pipe and use insulated rooftop containers (luggers, reservoirs on mechanical
applicators, mop carts, buckets)
Keep the lids of rooftop containers closed except when necessary to fill them
For additional information and guidance, contact ARMA
The ASTM D312 maximum kettle temperature of 550°F (288°C) is critically linked to the minimum flashpoint of 575°F
(302°C) specified in the standard. When using BURA reporting flashpoints below 575°F (302°C) (for example, under
the CSA standard, asphalts may have flashpoints as low as 518°F (270°C)), the kettle temperature must remain at
least 25°F below the flashpoint at all times. Additionally, it is good practice to limit the heating and storage of
asphalts at 500°F (260°C) or higher to less than 4 hours. All temperatures should be measured with properly
maintained and calibrated devices once the asphalt and kettle have reached a steady state temperature and the
asphalt has been skimmed if needed. If a thermocouple or thermometer is used, it should be inserted into the
asphalt until a constant temperature is achieved. If an infrared gun is used, follow the equipment instructions for
distance and point it at a freshly disrupted asphalt surface to get the best possible reading.
All practical measures to reduce worker exposures to asphalt fumes should be used on every BURA job. In addition
to good temperature management practices as discussed above, a number of work practices, equipment controls,
and innovative products are available. Information on these exposure control measures is available from ARMA.
1
Follow manufacturer recommendations for storage of packaged and bulk asphalt. Prior to use, cartons should be
stored in a way that protects them from weather, debris, and sunlight, and that prevents cold flow of the asphalt
from fallen cartons or excessive material stacking. Asphalt kegs should be stored in an upright position, single or
double stacked, and protected from moisture and adverse weather conditions that could degrade the packaging or
product. Application will be affected by surface and air temperature, wind conditions, as well as other
environmental factors. For interplay mopping and flood coating, follow the directions of the roofing manufacturer. Read more
Introduction
Asphalt shingles have been used successfully in various climate zones around the world, including desert and tropical
regions, for over one hundred years. Improved application efficiency and, more importantly, enhanced long-term
shingle performance can be achieved by following the recommendations outlined below for hot weather storage
and application.
Storage Prior to Use
Always follow the manufacturer’s precautions about stacking bundles and pallets; stacking bundles too high or
double-stacking pallets can indent or deform the shingles over time, particularly in warm weather or when shingles
are exposed to direct sunlight. As a general rule in hot weather, store shingles in a cool dry place in stacks no more
than four feet high. If higher stacking is necessary, it is recommended to use racks or bins so that the weight of the
bundles on the upper pallets does not bear down on the bundles below. Systematically rotate all stock so that the
material that has been stored the longest will be the first to be moved out (i.e. first in, first out).
Although asphalt shingles are designed to withstand direct exposure to the hot summer sun after installation, it is
best not to store the products in direct sunlight prior to installation. Storage in direct sunlight may also cause a
weathering and weakening of the packaging materials, making it awkward to handle the bundles prior to installation.
Removing Shingles from Bundles
Although shingles have a release film to prevent them from sticking to each other in the package, direct sun can
cause the sealant to become more aggressive, making the shingles more difficult to separate and remove from the
bundle. When removing shingles from a warm bundle, follow the manufacturer’s recommendations; some products
may separate better or more easily when removed from the bundle “granule side up” or by quickly snapping the
shingles out of the bundle stack. This helps break the weak bond which may have formed between shingle sealant
and release films, allowing easier separation and minimizing potential shingle damage.
Placement of Shingles on Roof Prior to Installation
Shingles should be kept in bundles or handled in pairs and stacked squarely to maintain shingle sealant alignment
with the release tape until applied. Asphalt shingles become more flexible in hot weather, so avoid rough handling
that may tear the shingles or break the laminating adhesive bond on multi-layer shingles.
Keep bundles as flat as possible during the roof loading process and on the roof.
Do not drape shingles or bundles over the hips or ridges; keep shingles in their packaging until ready to be applied.
During Application
Always be careful when working on sloped roofs. In hot weather applications, the asphalt coating on the shingles will
Recommendations for
Storage and Application
of Asphalt Roofing
Shingles in Hot Weather
soften. Wear soft-soled footwear to minimize foot slippage possibilities and scuffing of the shingles. On steeper
roofs where worker footprints, such as toe or heel marks, are likely to be more concentrated in small areas., use
reasonable care to minimize scuffing and, if necessary, wait until the shingles and ambient temperatures cool.
Ensure roof safety by following all required safety precautions; such precautions should include use of fall protection
devices.
For comfort reasons as well as the safety reasons noted above, on forecasted hot and sunny days it is advisable to
install shingles early in the day before the temperature reaches its maximum. One should also plan the roof
installation to “work around the sun,” i.e. work on the west – and south-facing slopes in the morning and the eastand north-facing slopes later in the day.
In hot weather, shingle pieces trimmed for hips, ridges, rakes, and valleys can quickly adhere to shingles that are
already applied if left on the roof with their sealant strip down. Use good housekeeping practices to minimize shingle
debris on the roof.
Other Considerations
Most asphalt shingles are manufactured with a thermally activated asphaltic sealant which bonds the shingles
together once they are applied to the roof and exposed to a sufficient period of heat from sunlight. If this sealant has
been affected (blinded) by wind-blown dust from the surrounding environment or the job site (e.g. saw dust), the
sealant may not activate even on hot sunny days and the shingles will need to be manually sealed per the shingle
manufacturer’s instructions. On north-facing or steeper slopes the shingles may not seal immediately even in
warmer weather and may require manual sealing as well.
If repairs or other rooftop work is required during hot, sunny weather on existing shingled roofs, the shingles will be
susceptible to the same scuffing and possible damage noted above. Because the shingle sealant bond on existing
roofs is likely to be fully formed , their removal or repair will be difficult to perform without causing shingle tearing
and damage at the sealant interface. In such cases it may be best to wait until the shingles are cooler before
attempting shingle repair. If waiting is not feasible, lightly spraying the shingle surface with a water mist will cool the
shingle surface and may facilitate sealant bond separation. Caution: A wet roof surface can be slippery, so take
appropriate precautions.
Snow and ice accumulation on steep-slope roofs can lead to ice dams at the roof eaves. Ice dams are
typically formed by the repeated thawing and freezing of melting snow or backing up of frozen slush in
gutters. When ice dams occur, water can be forced under the roofing materials and may cause damage
to a home’s ceilings, walls and insulation, and long-term damage to structural components.
The installation of an ice dam protection layer along eaves is recommended to protect against leakage
from ice dams. Per the International Building Code and the International Residential Code (IBC and IRC),
in areas where there has been a history of ice forming along the eaves causing a backup of water, an ice
barrier shall be installed. The International Residential Code (IRC) refers back to the local authority
having jurisdiction. There are two methods of creating an ice dam protection layer. The installation of a
polymer modified bitumen self-adhering underlayment that complies with ASTM D1970 (one layer) is one
approach, as recognized by the current version of the IRC. It is ARMA’s recommendation that the product
should be extended a minimum of 24 inches (610 mm) inside the interior wall line of the building. There
are some jurisdictions that will require eave protection to extend further up the roof slope, and other
jurisdictions that will call for less. In all cases, apply per the roofing manufacturer’s installation
instruction and your local building code.
As an alternative, use two layers of asphalt saturated felt as the ice dam protection. Thoroughly adhere
the felts to each other with a continuous bed of plastic cement from eaves to a point at least 24 in.
inside the interior wall line of the building. Begin by applying the felt in a 19 in. (483 mm) wide strip
along the eaves, overhanging the drip edge by ¼ to ¾ in. (7 to 19 mm). Place a full 36 in. (900 mm) wide
sheet over the 19 in. (483 mm) wide starter piece, completely overlapping it. All succeeding courses will
be positioned to overlap the preceding course by 19 in. Refer to the roofing manufacturer’s installation
instruction and the local building code for any additional requirements.
#image_title
Description
Buckling is the result of asphalt shingles not lying flat due to wrinkling of the roofing underlayment or movement of
the wood deck.
Causes
• Exposure of the wood roof deck during new construction or roof replacement can lead to moisture
absorption into the wood. As the wood increases in moisture content, movement of the decking can occur.
• As a new roof is installed, moisture can be trapped in the system and the roofing underlayment can absorb
moisture and wrinkle.
• Inadequate ventilation of the attic space, which restricts free-flow of air directly beneath the roof deck, can
create problems with moisture and temperature management in the attic space that can contribute to
movement of the wood deck. See individual manufacturer recommendations for ventilation requirements.
• Roof decking that is not spaced a minimum of 1/8” can cause buckling due to expansion.
Solutions
• Allow moisture to escape the roofing system. Once the roofing system reaches the proper moisture content,
the roof should lie flat and the buckling problem should not return.
• Remove the shingles that are affected, and where the felt is wrinkled, repair the wrinkles by cutting and renailing the felt so that it is flat, and then replace the shingles.
• Ensure that the attic is properly ventilated according to the latest version of the building code. Proper
ventilation includes free-flow of air directly beneath the roof deck, from the eaves to the ridge.
Prevention
• Use only wood decking materials acceptable to the roofing manufacturer that have been properly
conditioned. Refer to detailed recommendations found in the “How to Minimize Buckling of Asphalt
Shingles” published by APA – The Engineered Wood Association.
• Do not expose decking materials to liquid water either before or after application.
• Cover wood deck materials with asphalt-saturated felt shingle underlayment (ASTM D 226, ASTM D 4869,
ASTM D 6757 or CSA A123.3), then apply shingles as soon as possible.
• Ensure adequate attic ventilation (e.g., a minimum of one square foot net free area per 150 square feet of
attic floor space). See individual manufacturer recommendations for additional ventilation requirements.
• Apply shingles in accordance with shingle manufacturers’ recommendations.
Correction
• Ventilate the attic space to eliminate excess moisture. In some circumstances, the addition of mechanical
exhaust fans may be necessary.
• When buckling persists, remove and replace the affected underlayment and shingles.
The International Building Code (IBC) and the International Residential Building Code (IRC) require that roofing nails
be utilized to fasten asphalt shingles. Proper nailing is essential to good performance. To ensure proper nailing
during shingle application it is required that you follow the IBC and IRC nail requirement guidelines. The Asphalt
Roofing Manufactures Association (ARMA) supports these requirements, (several of them referenced below) as well
as additional installation recommendations outlined below.
Nails are required to have a minimum nominal shank diameter of 12 gauge (0.105”) and a minimum head
diameter of 3/8”.
Nails should be corrosion resistant. Nails are required to be galvanized, steel, stainless steel, aluminum or
copper roofing nails. Galvanizing by various processes is the typical means of achieving corrosion resistance.
Aluminum roofing nails do not require additional coatings for corrosion resistance.
Select nails long enough to penetrate ¾” into the roof deck. If the deck sheathing is less than ¾” thick, use
nails long enough to penetrate the roof deck sheathing and extend at least 1/8” beyond the lower side of
the roof deck. In determining nail length, consider the number of layers of shingles, shingle thickness(es),
underlayment and flashing (eaves, sidewall and valley, etc.).
o In some cases, the underside of the deck is exposed to view. In this case, using nails of the
recommended length will result in the nail points penetrating through the deck and being exposed
to view. Consult the roofing material manufacturer and building code requirements for approved
alternatives if visible nail points are considered aesthetically objectionable.
All nails are to be driven by hand or with a pneumatic nailing tool that has been properly adjusted to
correctly drive the nails. Failure to use a properly adjusted pneumatic air system can lead to sealing failures,
raised tabs, buckling, and blow-offs.
For most asphalt shingles, a minimum of four nails is required. For some shingles and for some application
circumstances, the required number of nails may be different. The specific recommendations of the shingle
manufacturer, as printed on each shingle wrapper, must be followed to ensure the intended performance
and compliance to building codes.
Placing and Driving Nails
Improperly positioned and driven nails can lead to sealing failures, blow-offs, raised tabs, and buckling. The following
practices reflect the general recommendations of most shingle manufacturers. However, the recommendations of
the specific shingle manufacturer, as printed on each shingle wrapper, must be followed when applying shingles.
Align each shingle carefully. Make sure the cutouts or end joints are more than 2” from any nail or end joint in the
underlying course. Start nailing from the end nearest the previously-installed shingle and proceed across. This will
help prevent buckling. To help prevent distortion, do not attempt to realign a shingle by shifting the free end after
more than one nail is in place.
Critical aspects of nail placement include:
Never place nails where they will be fully or partially visible after the roof is complete.
For most shingles with sealant on the top surface, place nails below the sealant strip but above the area that
will be visible after the roof is complete.
Shingles with sealant on the back surface often have a line or lines to indicate the location on the shingle
surface where the nails are to be placed.
Nail Application of
Asphalt Strip Shingles
for New and Recover
Roofing
2 of 2 A member service provided by the Asphalt Roofing Manufacturers Association Revised 5.16.2018
No nail head should be closer than 1″ from either end of the shingle. Specific recommendations from the
shingle manufacturer for positioning the nails across the shingle are included in the manufacturer’s
installation instructions.
Do not drive nails into knot holes, cracks or spaces in the roof deck.
Nails are to be applied so that the entire head bears tightly against the shingle.
Nails are not to be underdriven, overdriven (to break or cut into the shingle) or driven crooked. See Figure 1 for
examples of properly and improperly driven nails.
Repair incorrectly applied nails immediately. Underdriven nails can be tapped down. Remove overdriven or crooked
nails, repair the hole with asphalt roof cement complying with ASTM D4586, and place another nail nearby. If this is
not practical, replace the entire shingle.
Ponding water is defined as water, which remains on a roof 48 hours or longer. It may result from rain, melting snow/ice or
runoff from rooftop equipment. The Asphalt Roofing Manufacturers Association is joined by many reputable organizations, such
as the National Roofing Contractors Association, the Midwest Roofing Contractors Association, the American Institute of
Architects, and the International Institute of Building Enclosure Consultants in recommending that roof designs provide
adequate slope (usually min. ¼” per foot) to ensure that the roof drains freely throughout the life of the building, thereby
lessening the potential adverse effects of ponding water.
If not addressed, ponding water may result in significant consequences including but not limited to:
Deflection/Deformation: As water accumulates in ponding areas, the load on the roof increases, and may result in deck
deflection. The potential for deck deflection increases with the capacity of the area to hold water thereby increasing
the potential risk to the structural integrity of the deck.
Ice Damage: Ice formations develop and move constantly with changes in temperature. This movement may “scrub”
the roof membrane to an extent that physical damage to the membrane may occur.
Biological Growth: When water stands for long periods of time, it promotes biological growth, such as algae and
vegetation. Damage to the roof membrane may occur from chemical and physical attack from the bio-growth as well
as the expansion and contraction of the bio-growth during wet and dry cycles. Additionally, vegetation and other
debris may clog drains and cause additional ponding.
Dirt/Debris Accumulation: Accumulation of dirt and debris may support biological growth. If a ponding area dries, the
accumulated dirt and debris may contract during dehydration (resulting possibly in “alligator cracking”) and pull at the
surface of the membrane.
Water Infiltration: If roof membrane integrity is compromised, the risk of water infiltration into the building and
subsequent interior damage is amplified.
Best practices to avoid ponding water are as follows:
A roof’s structural frame or deck should be sloped, and drainage components such as roof drains and scuppers should
be included.
Regular maintenance to ensure drains remain unobstructed so that ponding water does not occur due to clogged
drainage systems.
If a deck does not provide the necessary slope to drain, a tapered insulation system may be used to create positive roof
drainage.
Crickets installed upslope of rooftop equipment and saddles positioned along a low-point between drains, may help
minimize localized ponding in conjunction with a tapered insulation system.
Rooftop HVAC condensate lines should be connected to proper drains to prevent condensate from draining onto the
roof.
If ponding water does occur, efforts should be taken to eliminate or reduce the accumulation and persistence of water on the
Effects of Ponding Water
on Low Slope
Roof Systems
2 of 2 A member service provided by the Asphalt Roofing Manufacturers Association Revised August 2019
roof surface. Failing to address ponding water may shorten the effective life of the roof membrane system.
To obtain specific information regarding the effects of ponding water on particular products and systems, contact the individual
roofing material manufacturer.