Ice dams – and the water leaks they cause – are a constant threat to sloped roofing systems in colder climates. Unfortunately these pesky ice dams, an effect of winter’s freeze-thaw cycles, are not always preventable or fully diagnosable.
To help prevent the negative effects of ice dams – roof leaks – during the cold months, it is important to have your roofing system installed in a way that exceeds code regulations. After all, the roofs most susceptible to leakage after the formation of an ice dams are those that have been poorly built or poorly designed.
How Ice Dams Form
In the winter months, the snow on your roof experiences alternating periods of melting (due to heat loss from the home, high daily temperatures or the warmth of sunshine) and freezing. Often, the snow that melts on the rooftop will re-freeze on the eaves, which are usually colder than the rest of the roof.
However, as the water re-freezes on the edge of the roof, it slowly increases in size and backs up into the rest of the roofing system. When an ice dam begins to form, natural drainage is hindered. If this buildup of ever-increasing ice finds its way under the shingles and into the roof itself, homeowners begin to notice leaks in their homes.
Industry and Code Requirements
The contractor who designs and installs your roof is required to meet any applicable building codes. These codes are typically viewed as minimum requirements that are always able to be exceeded. A reputable contractor will exceed all code requirements when installing a roof on your home, in the interest of superior protection and durability.
Many state and local officials specify the regions when it is required to use an ice barrier or additional waterproofing in the system.
Basically, the code requirements are set in place to ensure that the product placed on your roofing system has self-sealibility and maintains its waterproof integrity when exposed to water. These characteristics are tested by pounding 2 nails through the membrane, then pulled out ¼”. This section is then exposed to several inches of water for three consecutive days.
Ice Barrier Protection Considerations
Every home should have an ice barrier membrane included in the roof system installation. This protects your home from various conditions that are not always considered in general building code requirements, including:
- Ice & water accumulation – most codes fail to specify the regions that are at an increased risk of ice dams, since these factors are affected by other considerations such as the architecture and slope of the roof, exposure to the elements, etc. The unique considerations of each home should be assessed by the roofer who constructs the roof on your home.
- The geometry of your roof – complex roofing systems with many peaks and valleys are at an increased risk of ice dam formation than homes with a simple A-line roof.
- The type of roof on your home – the materials used on your roof also affect the probability of ice dam formation on your home. For example, shingle roofs with steep slopes can more easily shed snow than those with lower slopes, and metal roofs shed snow most easily.
What Type of Ice Barrier Should I Put on My Roof?
Although all products must pass our current building codes, they differ greatly in terms of their abilities. Some adhere better to the roofing system, others might be easier to handle. Some products are also backed by better a better manufacturer support team.
Here are a few considerations:
- Rubberized asphalt-based adhesive typically performs better than those that at butyl-based.
- Membranes that adhere to the roof immediately when installed are often better than those that require heat application.
- Membranes that are more flexible can be installed with greater precision.
- Using a primer to improve the bond between the membrane and substrate (plywood roof deck, etc) enhances the performance of the ice barrier.
- Special mastic/roofing cement can be used atop the ice barrier in regions that are likely to collect snow.
- A special membrane installed beneath the ice barrier that is often more durable than the mastic.
The Importance of a Quality Roof Deck
Many homeowners simply think that “gutters and eaves” are the answer to their ice dam problems. However, one of the most important components to a waterproof home is the substrate preparation.
Preparing the Substrate
The substrate (plywood roof deck, etc.) should be adequately supported and have smooth joints. An uneven substrate can tear the ice barrier membrane or fail to adhere properly, eliminating its waterproofing abilities.
A roof deck that is warping or separating poses a variety of problems to the proper installation of a roofing system, and may require significant work to keep it intact and limit the movement that poses a threat to any waterproofing membrane.
Reputable roofing contractors in regions that are subject to ice dam formation have a responsibility to design and install roofing systems that are made to stand up to the test of weathering. Since not even the best-constructed roof will always prevent ice dams, it is imperative that an appropriate waterproofing ice barrier be installed to keep the homes of our clients safe.