Snow and Ice on Sloped Roofs: Shed it or Keep it on?

How would you answer this question? If you are like most roofing consultants, you would reply based upon a number of factors.  One factor would be your experience as a roofing expert.  Another would be where you live and work.  Another factor would be your training.  If you are from North America you would probably respond “shed it off.”  Our approach in North America is to use a metal roof with a steep slope that will allow the snow and ice to slide off.  Why do we design this way?  The primary reason is a fear of having the building collapse under a heavy snow load.

As I design roofs today in ski resort areas, I use one of the above types of roofs and plan to keep the snow on.  I vent the roofs for many reasons:

If you lived in Europe, however, you training and experience would be notably different.  For instance, a roofer in Germany must apprentice before he can become a journeyman. (This compares to our weekly union program that involves very little training on sloped roofs in snow climates.)  A German apprentice’s training includes classroom and onsite work.  Manufacturers sponsor training and provide detailed reference books and manuals.  One key difference in industry’s approach to snow on roofs is that keeping snow on the roof is something that they desire-quite the opposite from the trend in North America.  They would say “use a low slope (approximately 5/12) and keep the snow on.”

In an effort to solve the problems associated with moving snow and ice, I have heeded the experience and resources of European construction industry and have implemented their ideas with great success.  Here are some of the key factors in their approach to keeping snow on the roof.

Germans in general are not concerned with snow loads because they design the structure to hold the live load.  Designers there want the architectural freedom to have access around the building.  They also plan to use the snow as an insulation blanket and design a cold roof system to stop ice dam concerns at the eave.  The slope that works best seems to be 5/12.  This allows the snow to stay on while venting the roof system.  They then have the option of putting dormers on the roof without damage to the valleys, penetrations, lower roofs, and property below due to sliding snow and ice.

snow retention

snow retention

To complete this roof system, snow stops (or snow brackets) are used to stop all snow movement.  In Europe the majority of roofs are tile.  Many of the tile manufacturers make field tiles with snow stops as part of the tile. (See tile photo.)  Through extensive testing, they have found the snow stop’s fail point.  Once they know this, they engineer charts which help the consultants calculate how many snow stops are needed from eave to ridge based on roof slope and snow and ice loads to effectively hold the snow and ice on the roof.  With this information, European designers create roofs that effectively hold the snow and ice in place, as well as preventing roof damage and breakage. (See German chart, page 25.)

snow retention, snow bracket

I have found that if you want to stop damage to the roof from snow and ice, you must stop movement.  Snow fences do not do this, but properly placed snow bracket do.  In my research, I have found different conditions which require snow fences and/or snow brackets.  Snow brackets stop the movement of the snow on the entire roof.  They are typically installed over the entire roof.  Snow fences are meant to stop top-layered snow from sliding off like and avalanche over doorways.  These snow fence brackets normally attach to the rafters on two-foot centers.  If the eave-to-ridge length is over 20 feed, European designers usually place another snow fence row mid-span.  Both snow retention items are sometime necessary.  But without designing the snow retention based on accurate testing, you could be wishing you had that steep slope and metal roof (which was always intended to shed snow).  It is critical that a designer specify enough snow retention devices based on the slope and snow load.

It makes sense when designing a metal roof to shed snow, not to keep it on.  With expansion and contraction of the metal, it is difficult to attach snow retention devices into the roof decking without causing a roof leak or slotting of the metal panel from the snow bracket fastener.  If you attach only to the metal, the metal sheets can be torn off because of the use of expanding sheet clip system and the weight of the snow being held on.

The following roof types are good for keeping snow on:

  1.  Tile
  2. Asphalt shingles
  3. Wood shakes
  4. Slate

number of snow brackets, snow retentionWhen using these types of roofs, it is I important to know which climate you are in (i.e., number of freeze-thaw cycle and altitude and how to control vapor drive and ice damming.  These factors will make a difference in the roof design.  A cold roof system which controls these factors is ideal roof system.  In the cold regions of Europe, the roofers have manuals with detailed specification, details, graphs, and charts which explain cold roof system and how to successfully install them.  This is one reason keeping the snow on the roof is such a widely accepted practice-the roof are planned for it and installed correctly.  In the U.S., there is a manual on roof applications in heavy snow areas prepared by the Western State Roofing Contractors Association (WSRCA) and the National Tile Roofing Manufacturers Association (NTRMA).  This manual promotes the cold roof system and snow retention.

  1. To reduce ice dams and icicles.
  2. To exhaust vapor from the building.
  3. To extend the life of the underlayment.
  4. To provide an insulation blanket on the roof.


I follow Austrian venting charts for duct work size from eave to ridge.  I also pay close attention to air intake and exhaust size because many screens reduce air flow by up to 70%.  Then I install snow brackets and snow fences on the roof per manufacturer’s engineering design from eave to ridge.  With this I had great success in Sun Peak, Canada; Grand Targhee, Wyoming; Bear Creek, Colorado; Sundance, Utah, and many more.

Note: this year a manual called Concrete and Clay Tile Roofing Design Criteria Manual for Cold and Snow Regions was commissioned by NTRMA and WSRCA.  The manual helps determine the climate type and explains what design factors are important in the given zone.  It also explains essentials such as ice damming, vapor drive, and ventilation for cold roofs and includes venting charts.  For further information, phone WSRCA at (650) 548-0112.


  • Anderson, Terry, and Gillan, Leland, Concrete Clay Tile Roof Design Criteria manual for Cold and Snow Regions, WSRCA & NTRMA, 1998.
  • Braas Tile Venting Manual
  • Bramac Brochure on Venting, March 1996
  • Redland Roof Tiles Limited, 1998
  • WSRCA/NTRMA Cold Roof Committee
  • Zander Tile Roof Installation Book

By: Terry Anderson

Published: Interface January 1999

Download (PDF, 674KB)

Power of Ice – Sliding Ice & Snow Causes Roof & Property Damage

snow and ice, snow retention

By: John Del Grosso

Published: Architectural West | March/April 2003

The power of snow is seldom apparent as each unique snowflake falls to the ground.  Yet, when snow accumulates on the roof, the damage that can be caused by sliding ice and snow is a major concern.  Tim Ryan, president of the Arrowhead Condominium Association, a Private Unit Development, and head of the property-management firm for the association has firsthand experience in dealing with sliding ice and snow.

Located in Big Sky, Montana, the Arrowhead Condominium Association consisted of 24 units with metal roofs and a 12:12 slope.  These homes are only 10’ to 15’ apart, and each is a ski-in/ski-out unit on a hillside.  During harsh winter weather, the snow, ice dams, and icicles were sliding off the units and damaging neighboring homes.  The front door of one unit even collapsed three different times.  The decks on the buildings had to be closed for the winter, since many rails and decks had been torn off.  On lower shed roofs, not only was the metal roofing torn and bent, but the ¾” plywood sheathing was crushed between the roof’s rafters.

On several occasions, Ryan had worked with the Association’s insurance company assessing the damage.  The insurance company said it would not renew its policy due to the continuing problems.  “Their concern of the ice and snow killing someone was too great,” noted Ryan, “We did not know how to eliminate these problems, so we called Locati Architectures of Bozeman, Montana. They referred us to Terry Anderson of Anderson Associates Consulting, Inc.”

Anderson, who is the co-author of The Cold Roof Manual, published by the Western State Contractors Association and the Roof Tile Institute (RTI), visited the project to review all the damage and concerns.  He concluded that the only way to solve the problem was to stop the movement of ice and snow.

“Anderson recommended an engineered snow-retention system,” Ryan continued. “He also recommended a good ventilation system that, once installed, would stop most of their ice dam and icicle problems.  He visited with the board and gave them several roof options.  After reviewing the choices, the Arrowhead Condominium Association chose concrete roof tiles.  The association felt the concrete tiles had the longest record of use in Europe using a cold-roof design.  They also liked the look of the tile.”

snow and ice, snow retention

After Anderson Associates wrote the specifications and details, the project was bid out to qualified roofing companies who were familiar with the specified cold-roof system.  Trojan Roofing, from Salt Lake city, Utah, was selected.  The choice of all parties was concrete tile produced by Westile, Inc. of Denver, Colorado.

Since ground snow loads increased after the units were built, Anderson Associates hired a local engineering firm to check the structural integrity of the building for retaining snow and ice on the roof.  Securing the rafters properly to the plate-lien and purlins was the only minor change that was required.

Because it was late in the year and winter was approaching, the Arrowhead Association chose 14 of the 24 united to be reroofed immediately.  It was difficult for Trojan Roofing to work in the cold and snow conditions, but it gave all involved a great opportunity to see the difference between the old and new systems.

Many of the homeowners were concerned that the building could not retain snow on a 12:12 slope.  Anderson worked with the homeowners, assuring them that with proper engineering of snow fences and snow brackets, the roof system would retain the snow and ice on the roof.  The system was designed using a fully engineered snow-retention system with TRA Snow Brackets.

“Neither the homeowners nor the association understood what a cold-roof system was and how it would stop ice dams and icicles” stated Anderson.  “We worked very closely with them, explaining that venting air below the roof tile and above the sheathing would make melting and freezing equal from eave to ridge.  We used the RTI and WSRCA Cold Roof Manual and air ventilation charts from Europe.”

Since adequate ventilation was critical to the success of the roof system, Anderson calculated the air-duct size needed from eave to ridge.  He then designed an air-intake system from the eave and a ridge exhaust system in a raised-ridge vent.  Everyone involved was pleased to see the major difference from the old to new system, which was immediately apparent when icicles were eliminated and snow was retained on the roof.

snow retention

Homeowners of the first reroofed units were very pleased with the results.  The owners commented on how exceptional the tile looked with all the copper flashing and the copper TRA Snow Brackets.  The real proof of the improvements between the two roof systems became clear as the snow began to fall; the difference in the two roof systems was obvious.  The newly designed cold-roof system allows the snow to compact naturally with ice in the bottom 3”.  This ice freezes around the triangular portion of the TRA Snow Bracket.  This permits the natural run-off of water to shed between the ice and the roof tile when the outside temperature was above freezing.  Photos were taken to show the other property owners, who are all over the U.S., the improvements.

“The new units have stopped all snow and ice movement as well as icicles,” stated Ryan.  “The old units still have leaks, icicles, ice dams, damaged decks and snow and ice hazards.  Our association and homeowners are very happy with the look and design of the units.  We are looking forward to having the last ten units completed this spring and summer.  Retaining the snow on the roof has also reduced the heavy snow-removal cost.”

According to Ryan, “Credit needs to go to Anderson Associates Consulting, Western State Roofing Contractors Association and the Roof Tile Institute for the work on the Cold Roof Manual that made this system possible as well as the great work done by Trojan roofing while working in such bad winter snow and ice conditions.  The units look beautiful; they are safe and insurable,” concluded Ryan.

Download (PDF, 377KB)

Environmentally Friendly- Green Roofing and Snow Retention Meet at Schweitzer Mountain

snow retention, green roofing

By: Heidi Ellsworth, HJE Marketing

Published: Architectural West | May/June 2000

Where do green and white meet to create gray? In Sandpoint, Idaho at the hand of Tim Boden of Boden Design Mountain Architecture.  With a lifelong love of skiing and strong commitment to the environment, Boden has built a strong architectural business on a mountain in Northern Idaho.

The project was The Glades at Schweitzer.  Boden had been working on the project for a number of years, although he was not the initial architect on the project.  “We were looking for a special look that would run throughout the entire project,” states Boden.  “They had roofed some of the first homes using tile. Unfortunately the tiles were not the right match for the roof design in this area.  We were dealing with ice damns, ice sickles and roof damage so we needed to do something different.”

Situated at Schweitzer ski resort in Northern Idaho, The Glades development is owned by Basin Development of Pittsburgh, Pennsylvania. The development features second homes or vacation rentals for skiers.  Architecturally they are designed in traditional 1980s ski area/condo style with cutup lines and several valley’s ridges and hips.

Boden sits on the architectural control committee at Schweitzer and has led the Glades project for the past five years.  Not only has he worked on the project but also on his offices is located at Schweitzer, with his other office in Sandpoint, Idaho.  He has been working with the architectural design of Schweitzer properties for a number of years and it has offered him a great perspective.  “Often you have outside firms trying to design buildings for the area and they do not under the special challenges of the area,” continued Boden.  “We have made a career out of designing snow load and the particular tastes of our mountain audience.”

green roofing, snow retentionBoden and The Glades developer knew they had to find a different system.  The current tiles were cracking and breaking due to the movement of the snow and ice.  Snow slippage had destroyed tiles in the valleys chimney intersections and roof eaves.  The covenant, codes, and restriction (CC&Rs) of the Schweitzer Village called for the use of tile or shakes to be used for all steep roofing system.  “We have tried to establish a look throughout the Schweitzer resort that will last,” noted Boden.  “When the clay tiles didn’t work for us, I had to find something different for the new construction we were working on.”

And it wasn’t just the breakage that was a concern.  There was also the challenge of the liabilities experience with high density construction regarding snow slippage from roof structures.  “With village or commercial building construction, posted warning signs related to the overhead danger of accumulated snow slippage has not been enough,” noted Boden.  “People and property are injured or damaged each winter due to snow slippage.”

“The people of Schweitzer Mountain are realizing that holding the snow on the roofs is the safest consideration for commercial Village Construction.  Due to the dead load weight of accumulated snow, structural design along with methods and building materials selections need to be re-evaluated.  We consistently deal with 350 to 400 pound snow loads,” continued Boden.  “Outside the village, we can let some of the snow slide, so we do use metal roofs.  In the village itself we can’t let the snow slide due to pedestrians, skiers, and vehicles it needs to be held on the roof.”

In addition to snow loads, the owners, management and architects at Schweitzer had environmental considerations.  “This is a beautiful part of the country and we are all concerned about the quality of our environment,” noted Boden.  “When I look at new building products, building green is always a consideration.”

The Glades had been executed in two phases.  Boden did not design the first phase but worked with Terry Anderson of Anderson Associates Consulting, to solve the problem with the snow slippage.  For phase two, Boden designed the two new buildings using straight gables with shed dormers.  He wanted to look at a roofing system that would meet his needs for strength, snow retention and environmental friendliness.  It was recommended that he contact the management of EcoStar, Inc. the manufacturers of majestic Slate.  Majestic Slate is 100% recycled rubber slate tile.

green roofing, snow retentionI had to look similar to the roofing on phase one to meet the developments rules and maintain consistency throughout the project.  “Majestic did not have as much profile but was very similar in color,” noted Boden.  “I researched the product and then did some testing on my own.  Besides meeting a certain look, I wanted to be sure that it would work.   I put the products in my freezer and then took it out and did several tests for breakage.   It pasted all my tests and I realized that it could meet all our needs in addition to providing the look we wanted.”

“The glacier effect on the roofs in this area is tremendous.  The snow movement basically crushes the roof,” stated Boden.  “The testing I did on the Majestic Tile showed it had enough flexibility and strength to handle the amount of movement that might occur.  I also found that it would not absorb moisture and thus not cause problems from freeze thaw cycles.”

Majestic Slate is made of Starloy, a polymer blended of 100% recycled rubber and industrial plastic.  Starloy has been in production for over 20 years and used in the manufacturing of mats for docks, mud flaps and fatigue mats.  “From the history of Starloy, we knew that Majestic Slate was designed to endure cold, freezing temperatures and stress.  The product is also beautiful, made with the feel and look of natural slate,” continued Boden.

EcoStar Inc. prides itself on offering the most natural and progressive recycled roofing product on the market.  “We believe in creating a balance between the environment and economics,” stated Kerston Russell, president of EcoStar.

Besides the look and strength, Majestic Slate also offered ease of application.  “The Peter A. Chance Company worked with us during the installation process,” noted Ed Wininger, president of Everlast Roofing and The Glades roofing contractor.  “We found the installation to be very easy and the support from the Chance Company and EcoStar management exceptional.”

“I had my doubts about Majestic just because it was a new product on the market.  A lot of people have their doubts due to past new product problems.  After testing and using Majestic Tile, we are sold,” stated Winiger.  “There is a learning curve but once you get going it is easy.  You can score it with a knife and snap it.  You can also shave the ends once you cut it to give the cuts ends a finished look.  All our guys were intrigued by the product.”

“When comparing the installation costs of Majestic Slate to traditional slate or tile, there is quite a difference,” said Chris Olson, technical representative for the Peter A. Chance Company.  “The installation cost is lower due to the reduced weight, flexibility and ease of application.  Majestic Slate weight a quarter the weight of slate or clay tile.  The reduced weight allows more flexibility in the structural design process and in the inherent flexibility eliminates broken pieces during installation, transit and loading.”

In dealing with the extreme weather, Majestic Slate carries a 100 mph wind warranty and a 50-year product warranty.  “We foresee no problems with snow loads,” stated Russell.  “The raw material Starloy has been used for years in some of the most extreme environments.  That gives us the highest level of confidence in our products.”

In addition, snow retention devices were specified in conjunction with the Majestic Tile.  “We wanted to use a cold roof system,” said Boden.  “We again worked with Anderson Associates Consulting to develop a system for phase in junction with the Majestic slate.”

green roofing, snow retentionAnderson is also the developer of TRA Snow Brackets.  He recommended following the European style of snow retention by using snow brackets throughout the whole roof.   “The United States and Canada have different concepts about snow retention that Europeans,” stated Anderson.  “The first thing American think is to get the snow off the roof with a steep slope roofs in mountain areas to keep the snow as an insulation blanket.”

As Anderson was designing the TRA Snow Brackets he was also working on developing bracket failure ratio charts.  Working with Brigham Young University, through a grant from the State of Utah, he determined that a majority of the failures occurred from the pull out of the sheathing not the brackets.  “I wanted to create charts like those in Europe for the United States using my understanding of the fail points,” said Anderson.  “When I designed the charts, we developed them using a two to one safety ratio.  We also took the friction of the roof out since the roof friction can change the ratio.  The safety factor of two to one has lead to the success of the bracket.”

“The European system revolves around three points,” explained Anderson. “One, take any vapor that has escaped in other roof cavity above the insulation and then pull the vapor out through the ridge with venting air.  Two, stop ice dams by making roof temperature equal.  By venting air into cold eave, it becomes warm from the radiant heat of the house and then exits through the ridge vent.  This makes the temperature equal from eave to ridge and this is called a cold roof system.  Third, hold snow on the roof with snow retention brackets to create an insulated blanket and stop roof and property damage.”

To enhance the ventilation process, Olson recommended using Premier Highpoint ridge vents.  Highpoint ridge vents are made by NW Building Products out of Bigfork, Mont.  “We truly believe that Highpoint is a superior product,” stated Olson. “It is natural choice for high wind areas.”

The Premiere Ridge Vents is 18 square inches per lineal foot of unobstructed net free ventilating area.  It exceeded the Dade County Hurricane Test with its exterior wind baffle.  “Essentially, there is an integral airfoil that is at the lower edge of the ridge vent.  It diverts wind, wind drive rain and snow, up and over the ridge keeping the interior dry and protecting the ridge shingles from blow-off.  It also forces the ridge vent to act as an exhaust as intended by not permitting air to be blown into the ridge vent,” noted Olson.  “Also, due to the manufacturing process of using UV-stabilized polypropylene with self closing ends, High point vents withstand dramatic temperature changes and extreme structural loading.”

With snow retention devices, the Premiere Ridge vent and the Majestic Slate Tile, Boden had a complete cold roof system for his new construction.  In the case of the old clay tile roofs, that were not project to be reroofed, Anderson recommended fixing the slide and breakage problems with snow retention devices on the full roof slope of the roofing system to help retain the snow on the roof. “Due to the cut-up architecture of the roofs, we could not develop and adequate ventilation system.  The venting did not always line up so you would have dead-end venting.” Said Boden. “We followed Terry’s advice and installed snow retention devices through the roof and heaters at the eave for icicle control.

The end results are spectacular.  “This is the coolest looking stuff. The definition and the depth that the Majestic Slate is showing is more than we expected.  The installation and appearance of the slate with the copper snow retention brackets is great.  I am getting questioned everyday if we will use the material for all of our projects,” smiled Boden.

The bonus is that it is a green roof. “There is no downside. It is quality product that I made of recycled materials and is recyclable.  You are not giving up anything,” said Boden, “You’re using raw materials which would normally go into a landfill and making a product to use in the building trades.  This is just a win-win for everybody. It works and looks great. We have to use these sustainable products or our landfills will completely filled with old roofing.”

“Even though we are environmentalist we can’t push green building products unless they function, are aesthetic, and cost effective.  That is the future; products must be good for the environment and good for business. Majestic Slate is one product which does both,” concluded Boden.

Download (PDF, 721KB)

Concrete Tile Excels in Snow Country; Europe Shows How

By: Terry Anderson

Published: Interface | February 1997

Oslo, concrete tile roofs

Ruined penetration pipes, torn off gutters, broken tiles, damage to property below roofs and various other snow- and ice-related problems on concrete tile roofs are just a few of the complaints I have repeatedly received since I began roof consulting in the western United States.   After researching the problems in the U.S. and discovering that there were few effective solutions, I determined to look beyond our borders.  The solutions to all of these problems were found across the Atlantic Ocean in Europe, where concrete tile is both popular and performs well in snow and ice areas.

Monier Inc., the largest U.S. manufacturer of concrete roof tile, referred me to their parent company, Redland PLC, headquartered in England, I studied tile roofs in various parts of Europe, including England, Germany and Norway.  In the vicinity of Oslo, Norway, where winters are long and severe, tile roofs and were inspected in the heaviest snow areas.

In Norway, tile manufacturers from Zanda arranged a meeting for me with the head of the information division of the Norwegian Building Research Institute (the equivalent of ICBO or BOCA) where they were queried regarding the overwhelming choice for concrete roof tile in their country.  They opined that Norwegians are more concerned about life cycle cost, energy efficiency and fire ratings than Americans appear to be.  Concrete roof tile has fit their stringent requirements best.  Asphalt shingles were used to a small degree after World War II because of their low cost, but were replaced by tile again when the population could afford a longer lasting product.

Research in Germany indicated that most pitched roofs utilize concrete tile.  The pitches ranged from 10:12 in the lower land of Frankfurt but changed to 5:12 in the Austrian Alps, a practice opposite what I generally see in the U.S.

The standard practice in America is to increase pitch as you travel upward in elevation, as evidenced by A-frame cabins and steeper pitched roofs.  Why do pitches of roof drop from 10:12 in low snow areas to 5:12 in high snow areas in Europe?  It was discovered that the Germans and Norwegians actually want a “snow blanket” on their roofs.

I was familiar with the idea of using snow as an insulator.  Years ago, as a Scoutmaster, I would take my troop to the Klondike Derby (a winter campout held in February).  Some of the scouts would build snow eaves to sleep in.  Others brought tents.  The ones who slept in the eaves were warm.  The boys in tents often slept little because of how cold they were.  Obviously, the snow and ice of the eaves acted as an insulator and the temperature was therefore much warmer than that in the tents.  The effort to use the insulative properties of snow on roofs in rural areas of Norway and Germany was astounding.  I saw centuries-old stone and slate buildings with low pitched roofs that actually had boulders placed on the roof to help hold the snow in place!

Snow and ice damage is almost non-existent in Norway and Germany.  Designers and roofers use a double-vented cold roof system to keep the temperature just below the tile at 32 degrees.  This creates compacted snow and stops icicles and ice dams caused by heat loss from the building which melts the snow.  Working like a fireplace flue, cold roof systems draw cold air from outside through the roof soffit.  This air mixes with warm air in the attic and is vented out through a continuous ridge vent.  This mixed air in the attic is about 50 degrees on average during the winter.

To get the air under the tile close to 32 degrees, it is again vented under the roof tiles using 2×2 vertical battens.  This draws air from eave to ridge, venting it out.  When spans from eave to ridge are very long, vents are also placed midpoint.  Metal snow brackets are slipped over the tiles, interlocking between courses.  Some tile manufacturers from snow stops into the tiles themselves.  These hold the snow in place, prevent it from sliding and thereby avoiding damage to the tile, penetrations, property and people.

snow retention, Oslo

Underlayments used in Germany were limited generally to one layer of 20-pound felt over the roof sheathing and 2 x 2 vertical battens below.  Many roof in Norway had underlayment unfamiliar to me.  The decks were a tempered hardboard with an asphalt shingle coating applied, acting as decking and underlayment.  Neither of the two roofing systems included a bitumen or ice-and-water shield product.

These tiles have affixed concrete snow stops. Note the vented system between deck and tile, at right.

While studying in Germany I discovered that Braas (which is part of the Redland Braas Building Group) provides roofers with hardbound roof application books which include details like how many snow brackets to use and provide layout charts based on snow load and degrees of pitch.  Because of this support and the demand for tile, the majority of cold climate roofers in Europe are well educated about tile and know how to install it.

Today in these areas, architects specify concrete tile made with built-in snow stops or requiring metal snow brackets placed throughout the roof from ridge to eave.  In some cases, snow fences are also used.  The purpose of these fences is to prevent avalanching that sometimes occurs with layered snow.  I also found that because of the double vented cold roof system, ice was greatly reduced.  Copper gutters were widely used without any concern for them being torn off.  I found no evidence of bent penetration pipes or broken tile in valley, nor of any damage from snow and ice slippage.  All of these conditions have been pervasive on tile roofs in the mountains of the western United

Much of this “old world knowledge” was brought back to Utah and has been used successfully for the past two winters.  Europeans obviously worked through their snow and ice concerns centuries ago and have developed a tile roof system that will perform for centuries more.  Since their combination of low slope roofs, cold, vented attics and engineered place of snow brackets performs so effectively, the construction industry in the United States should take careful note.

snow retention

Download (PDF, 522KB)

Colorado Snows

Colorado snows, ski resort roof damage

By Terry Anderson, Anderson Associates Consulting

Published: Western Roofing – November/December 1997

(Editor’s Note: Terry Anderson has been involved in the roofing industry for 20 years and is the owner of Anderson Associates consulting in Highland, Utah.  He is a member of RCI and NRCA. Anderson also serves on the committee for tile roof applications in snow and ice areas for the Nation Tile Manufacturers association.  Anderson may be contact at (801) 756-9811.)

The Beaver Creek Ski Resort and Community is one of the premier ski resorts in the Rocky Mountains.  Built in the early 1980’s, this Colorado resort sports European design and feeling with tile roofs, stucco and stone exterior walls.  The feeling is one of entering a village in the Austrian Alps.

Colorado snows, ski resort roof damageEach year East West Resorts, which manages 16 property owner’s association within Beaver Creek, spent tens of thousands of dollars on the associations’ money to repair roof damage caused by sliding snow and ice.  Peter Dan, the vice president and general manager said, “Managing 16 associations is difficult enough without having large recurring expenses that are as unpredictable as snow and ice damage.”  Tired of spending so much money on the same problem each year, property owners gave him the task of finding a solution.

Most of the roofs were designed with a cold roof system because of altitude, temperature differential and snow loads ranging from 140-200 psf.  Roofs in the “core” area of Beaver Creek are a special blue-green Westile concrete tile.  Snow fences had been installed in isolated locations.  But each spring, after the snowmelt, East West resorts had the daunting task of supervising repairs in the same area of roofs throughout Beaver Creek.  Of all the standard upkeep and repair which was anticipated and budged for, replacing broken tile was one of the homeowners’ greatest expenses each spring.  From 1992 to 1995, Dan explored new ideas and suggestions given to him by roofing contractors, roofing consultants and snow retention device manufacturers with each assuring him they had the answer.

After years of this, the manager felt frustrated.  He realized what the problems were, but couldn’t find a solution.  These were his observations:

  • The ridge line designs are different heights which cause snow and ice from high ridges to slide into valleys on the lower ridges sides.  The field tiles are crushes as the snow and ice slides downward.
  • The greater the distance ridge and eaves, the greater the damage.
  • Snow fences weren’t working.  The snow load was not distributed evenly and weight of slipping snow and ice would come down on the snow fence, tearing them off in many cases.  Field tile would also break above and below the snow fence.  Dan determined that he needed a system that didn’t allow this slippage to begin at all.  He also noted fences were being destroyed where they stopped at the valleys and didn’t go to the other side of the valley.  This situation was causing unequal forces from each side.  Snow and ice from the roof area without snow fences slipped into the valley areas which did have snow fences.  This force would be too great and would break the tile.
  • Snow and ice would slide off the roof slow at first, extending over the overhang and eave one to two feet.  Then this compacted snow and ice would break lose.  As it fell, it would cantilever over the eaves course of tile, breaking the first course of tile and the damaging roofs and structures below.  Danger to people was great.
  • When there is a long run between eaves and ridge, more than just one row of snow fences was needed.  It would be better to follow the European way of installing fences, about ten feet apart up the roof, providing more equal loads on the roof and stopping tile from breaking high up on the roof.


In an effort to resolve this dilemma, East West Resorts searched again for a system or product that met these requirements: The system should be easily installed into the current tile roof system; would keep the snow and ice on the roof; be engineered based on the roof’s pitch and amount of snow and ice on the roof; and have minimal penetrations through the roof underlayment which would minimize the risk of leaks.Colorado snows, ski resort roof damage

Dan checked the loads his structures could hold and found that they were sufficient to hold the snow weight on the roof.  He was then free to keep the snow and ice on the roof and allow it to melt there.

In his quest, Dan found a product specifically designed for concrete roof tiles, Snow Brackets by Tile Roof Accessories, Inc. (TRA).  These brackets did exactly what he needed done: distribute the weight of the snow evenly all over the roof, prevent it from sliding, and allow the large amount of weight to be concentrated over the head lap of each tile and battens.  It could be easily installed by a unique attachment system to the tile and batten without putting any holes in the underlayment.  This was an idea he liked over snow fences.

But most of all, he liked the engineering which has been done by the Engineering Department of Brigham Young University.  There, technicians using specialized laboratory equipment had tested the brackets to a fail point in a laboratory and in the field.  After analyzing the data, they formulated charts showing how many brackets should be installed based on pitch and snow load.  (TRA uses a basis of 2:1 failure with no friction)

TRA gave East West Resorts a specifically designed layout for the Beaver Creek buildings, showing how to place brackets based on the pitch and snowload.  Tim Simon of Premiere Maintenance Company was contacted about installed the brackets.  Brackets were ordered and custom powder-coated to a blue green color.

East West Resorts’ plan was to hem them installed on a few of the most troublesome buildings and see how they fared during the winter of 1996 and spring of 1997.  Dan chose four different roofs and four different exposures.  If the brackets worked during the winter of 1996, he would try some more the next year.

To Peter Dan’s surprise, the Snow Brackets worked just like he had hoped and during one of the heaviest snow years in Colorado’s recent history.  Dan said, “The TRA Brackets performed very well this past winter.  Out test areas were set up at several different exposures and roof configurations.  We used them on roofs with valleys, dormers and upper/lower roof designs and they performed superior to anything we have tried.  We are phasing Snow Brackets in each year on all our concrete tile roofs.”

Tim Simon, the roofing contractor who installed the snow bracket made this comment, “The installation of these snow brackets is very simple.  As the installer, we just had to figure the roof slope and the maximum snowload to come up with the calculation of how many snow brackets to install per square of roof.  One this and the installation pattern are figured, they are placed very easily and quickly.”  TRA figured the layout pattern for Simon based on his snowload and pitch information.

Because of the great success this year preventing broken roof tile, East West Resorts is planning to try other snow brackets on some copper roofs in Beaver Creek.

Download (PDF, 533KB)

Codes and Roof Snow Retention

Published: Interface – March 2005

snow retention code, snow retention

Damage to flat seam metal roof

snow retention code, snow retention

Damage to flat seam metal roofing

Picture three feet of snow and ice sitting on the roof above your front porch.  The sun is heating the frozen snow, and your four-year-old son is riding the brand new bike he got for Christmas.  The codes that were followed when the roofing contractor installed the snow retention on your roof will protect you and your son from being hurt by snow that might fall off the roof, right?  What would you think if I told you there are no coeds to protect us from falling snow and ice?  Thousands of codes have been developed for construction all over the country.  However, roof snow retention has never been addressed.  Why do we stand by and allow millions of dollars of property damage and even deaths to occur every year from sliding snow?  Codes governing products, installation procedures, and standards are not in place to protect the consumer.  In fact, currently anyone can cast a wax snow guard, spread some cement on the bottom, tell the consumer how to install it without any testing whatsoever, and then market it.  Inferior products are out there with no consumer protection in place.  Roofers and roof consultants are left with the daunting task of judging whether or not what they are specifying and installing will provide adequate safety and effectiveness in snow areas.

As a roof consultant, what methods should be used to determine which types of snow retention products to recommend?  Are you assuming that the snow retention manufacturers have engineered their snow retention products from the fail point of the roof system?  Are the current U.S. codes providing the standard to assure safety from sliding snow?

snow retention code, snow retention

Dormers can be torn off

I began an investigation to answer these questions.  It has been my conclusion that architect, roof consultants, builders, and roofing contractors make a lot of assumptions concerning snow and ice, and we often fail.  The simple truth is that most snow retention manufacturers do not design their products from the fail point of the roof system, resulting in many failures!  There are no ICC codes for snow retention.  The norm for the roofing industry is to just do what you have done in the past or guess that three rows at the eave of the roof will be just fine.

snow retention code, snow retention

People and property below can be in danger

There is another industry that one would think ought to have taken a lead in this life-threading concern.  The insurance industry is often expected to pay for failures in adequate systems.  In the state of Utah, where I live, two children have been killed from snow and ice falling off roofs.  As you can see in the photos, snow and ice have caused death, vehicle damage, and roof and gutter damage.  What is the common reason for denying claims caused by falling snow and ice? An “Act of God,” not covered by the policy.

Is snow and ice falling off the roof truly an act of God?  It is true that we don’t have control over snow and ice movement on roofs.  Many respected members of the architectural and roofing consulting industries have claimed that snow guard and snow brackets simply do not work.  There is a bit of truth to these assertions as some of the photos display.  However, the majority of the time, good design and installation will prevent glacial snow and ice movement on roofs and prevent many unnecessary claims to insurance companies.

Comparing how Europeans and Americans design their snow retention systems explain some reasons why the standards in America are not working.  In America we have no standards, whereas in Europe, designers look at the potential fail points of the roof and then design the system from the starting point.

There are six key questions to ask when planning a roof snow retention system:

snow retention code, snow retention

  1. What is the sheathing type and thickness and how is it attached to the substrate?
  2. How is the snow bracket attached to the sheathing?  How many fasteners per bracket are required and what is the pullout load of each fastener in the particular type of sheathing?
  3. What are the fail point loads of the snow bracket?
  4. What is the slope of the roof?
  5. What is the ground snow load?
  6. Where and how might ice dams occur?

After they have gathered all this information, European engineers develop layout charts using all the data.  These charts include specific types of roof and snow brackets installed on different sheathing types and thicknesses, snow load, roof slopes, and the number of snow brackets needed per roofing square.  Then snow brackets are placed according to the layout charts from eave to the ridge, which eliminates all snow and ice movement.  This protocol results in placement of snow retention devices from eave to ridge, never just along the edge.

snow retention code, snow retention

Snow fences used alone were not able to prevent damage.

I have used the above steps on roof design project throughout snow areas of the U.S. and Canada and have had great success from following these six engineering guidelines.  The snow and ice is restrained in place across the entire roof.  It just melts in place in the spring, eliminating damage to people or property and so-called “Acts of God.”

I am currently working with local code bodies to submit a standard to the International Codes Council (ICC) requiring snow retention manufacturers to provide certified data from the fail point of the roof system and not just from the standpoint of the individual snow retention device.  Roof consultants’ support of new standards will improve our roofing industry and provide for the safety of people, property, and roof designs.  Until a comprehensive standard is accepted and approved, all roof consultants would be wise to work with manufacturers who will provide them with this type of comprehensive data and then design roofs in accordance with the six suggestions above.  This will help ensure customers are getting a quality design and protect consultants from lawsuits if someone is maimed or killed or property is damaged by falling snow and ice.

Let’s all work together as RCI members and see that such standards are adopted.  If you have question on this article or would like to help to push this stand please contact writer at (801) 756-9811.

About the Author: Terry Anderson has been involved in the roofing industry for over 25 years and is the owner of Anderson Associates consulting in Highland, Utah. He is a member of RCI, WSRCA, and NRCA. Anderson has also served on the committee for tile roof applications in snow and ice areas for NTRMA and WSRCA. He co-authored the Concrete and Clay Tile Roof Design Criteria Manual for Cold and Snow Regions, published by the NTRMA and WSRCA. Anderson has conducted research in Europe.

Download (PDF, 289KB)