Winter Climate Installation

Q. I am in the process of building large spec homes in Montana and was wondering if there were benefits to using these tiles to enhance a cold roof design?

A. Properly installed tile roofs actually create a sort of cold roof by the way they are installed. The space created between the tile and the roof deck allows for ambient air to cool any heat loss that may escape the roof system. This is one of the reasons that tile roofs are the preferred roofing material in alpine regions around the world. The method of installation in severe winter climates however is very important and I would suggest that you reference the TRI / WSRCA Design Criteria Manual for Cold and Snow Regions for more specific information regarding your roof. 

Q. Will your roof build up ice on edge of roof using 1000 lb per square slate? What is the BEST application method?

A. The formation of ice dams or icicles on the down-slope eave of any roof is usually the result of building heat loss that melts the snow on the roof which, in turn, runs down the roof surface until it encounters the colder, ambient air temperature at the eave where it freezes and accumulates. The best way to avoid this problem is to install the combination of good insulation and balanced roof ventilation. There are a number of ways to accomplish this but there are also many variations depending on the design of the building and roof structure. The best information regarding this fairly complex issue is the TRI/WSRCA DESIGN CRITERIA FOR CONCRETE AND CLAY TILE IN COLD AND SNOW REGIONS. If your roofer or designer do not have a copy of this book, you may order one from the Tile Roofing Institute at or let me know and I’ll see if I can have one sent to you. Concrete tile roofs can be the best solution for severe winter climates but it is essential that attention be paid to proper installation for these regions. In essence, the roof should be well ventilated, the tiles should be installed on a counterbatten system and snow retention devices should be considered to avoid the possible damage caused by cascading snow. There are many different ways to accomplish these tasks but the method you employ will depend greatly on the specific design of your project. 

Q. I have lightweight shake tile on my new house in AZ .and like it. So I was thinking of using it on a house I am building in Montana. See that you don’t recommend it and I understand that as the roofers won’t touch it up there. My question is- is the standard tile able to stand up to snow and sometimes – 40 below?

A. Standard weight tiles are much better suited to the rigors of the severe Montana winters although the method of installation will differ somewhat from how your Arizona roof was probably installed. Concrete tiles perform quite well in winter climates, provided they are installed with those elements in mind. The greatest threat to tiles in winter regions is sliding snow. Snow retention devices should be designed into the roof and a well balanced roof ventilation system should be built into the roof structure to avoid the build up of ice. There are a great many variables that become critical in these types of installations so I would encourage you to have your designer and builder consult the ‘Concrete and Clay Tile Roof Design Criteria Manual For Cold and Snow Regions’ published by the TRI/WSRCA. If your designer does not have this manual, he may want to order one from the Tile Roofing Institute. Their email address is 

Q. I am going to have to re-roof my home in Sun Valley, Idaho. It is cedar and I am considering using a lightweight tile. The roofers I have talked with all tell me that they do not recommend this type of product due to the severe freezing/thawing in this area. I have been told tile reps as well as by a distributor in Boise (where the weather is much less severe) that it would be OK. Unfortunately there are no installations of lightweight tile in this area (at least none that I have been able to find out about). Also, in looking at the info on your web site, it appears that proper installation in this type of climate is paramount. I suspect that the roofers in town may lack the specific knowledge required. I would appreciate your knowledge regarding whether or not the product would be appropriate and secondly, if appropriate, how might I be assured of proper installation? I don’t know if roofers would come from Boise for example or if a local roofer could be given information about proper installation to allow him to do a proper job.

A. In alpine regions subject to heavy snow accumulations, it is very important that tile roofs be installed in such a manner that ice damming and snow movement be kept to a minimum to avoid damage to the roof system and the tiles themselves. Proper ventilation and snow retention will typically prevent this type of damage but there is always the potential for extreme conditions to overcome even the best system designs. Standard weight tiles typically perform very well in these climates, even in less than perfect situations. Lightweight tiles can perform well when the system is meticulously designed and installed but may be more susceptible to damage if the system does not match the requirements. Since the design criteria for roof loads are so great in most alpine regions, the need for lightweight tiles is not usually an issue so we would normally recommend the use of standard weight products.

Q. I recently had a renovation done where they installed a rubber / membrane roof on the dormer because of the low pitch. In the winter however – snow builds up with a small layer of ice next to roof. Then it slowly slides to the edge where it falls off in an avalanche. My contractor said that if I used snow guards it may cause ice dams which would be worse. Is that true? What type of snow guard can I attach to a rubber roof?

A. Specific solutions to snow retention problems vary. The following is recommended for this particular case. Apparently, the roof slope is low enough to require a sealed membrane but not shallow enough to retain the snow pack. Certainly, snow retention would seem to be a viable solution but I’m unsure why your contractor would be concerned about ice dams since these conditions are not necessarily related.

Typically, ice dams are created when there is heat loss from within the structure that is sufficient to melt the standing snow which in turn, runs down the roof until is hits the overhang of the roof that is usually much colder which causes the snow melt to then freeze and gradually build up into an ice dam. This can be exhibited most commonly by the icicles that hang from your roof eaves.

From your description, it is not clear to me if you, in fact, do have the conditions that would result in ice damming but you certainly seem to have a situation that leads to avalanching that can be destructive and dangerous. I am not familiar with any snow retention devices that are designed to be installed on stand-alone sealed systems since all we deal with are clay and concrete roof tiles.

In any case, I cannot see where snow retention would result in ice damming. The thin layer of ice that forms between the snow and the roofing material is quite common and in many cases will form a bond between the roof and snow pack. Unfortunately, when the first warm weather comes, this bond can break and result in the sliding that you have experienced. While I’m not certain that he will have a solution, I would advise you to visit the following website: Perhaps if you could provide him with photos of your roof, he could suggest a solution.

Q. Can we use an existing EPDM membrane (5:12 pitch) for substrate in Minnesota?

A. Although EPDM is not normally installed beneath concrete tile, there is no reason that it cannot be used. It is important however, when using a sealed system, to provide adequate ventilation to avoid condensation problems. The use of a counterbatten system is also important in climates with severe weather.