Choosing the Right Roofing Material

Important Factors
Traditionally roofs are made from a roof slab and insulating and water-proofing layers which also serve as cladding. It should be noted that when we refer to roofing materials we mean the surface layer itself rather than the entire roofing structure. The extremes of the Russian climate require that roofing materials be frost and water-proof as well as strong enough to withstand the weight of snow. Some market specialists are convinced that the vast majority of roofing materials used in Russia are more than strong enough for the climatic conditions but the problem lies in their incorrect installation or in the inappropriate maintenance of the building. A particularly sad example of this was the collapse last year of the snow-laden roof of the Basmanny market in which a number of people were killed and injured.
The choice of roofing materials depends on a number of different factors. In the first place, you need to consider the type of roof. Angled roofs usually require extremely hard outer surface coverings like tiles or metal sheets with polymer coatings. Flat roofs on the other hand use softer materials like overlays and membrane coatings.
Aesthetic and architectural considerations also play a large role in the selection of roofing materials. “Depending on the type of building for the same angled roof you could use standard steel sheeting or brass on bitchumious base. The cost of these two materials varies largely but then so does the look of the final building,” says Zakhar Kalmykov, executive director at Ovental.
Similarly, different types of roofing materials have different requirements. “For example, clay tiles weigh a great deal and require a very strong construction frame. Metal sheeting is much lighter however it has strict requirements when it comes to warmth and humidity,” says Mr Kalmykov. When choosing roofing materials an important factor is also the commercial use of the building. For example, if the top floor is to include a restaurant then it would make sense to create a roof made out of transparent materials.
Another important aspect is the performance requirements of a particular roofing surface. “For example, during the construction of a business center on Sotsialisticheskaya Ulitsa in St. Petersburg the developer decided to incorporate a transparent roof. However St. Petersburg is not Nice. The desire to use a particular roof surface can go against its performance requirements,” says Mr Kalmykov. According to Georgy Sagalakov, chief engineer at Art-Grafik the choice of roofing materials can depend heavily on time, cost and reliability. “As a rule the reliability of the material is the one aspect that is left until the very last. Usually the client wants to complete everything as quickly as humanly possible,”

Roofing Materials for Angled Roofs
Angled roofs include domes, arches, mansards and other types of architectural forms. Usually the roofing materials are made out of extremely hard, water-proof substances. Even if a softer covering is used then the subsystem comprises a very strong load-bearing construction. Types of hard roofing materials include: metal, glass, tiles, asbestos sheeting, fiberglass and steel composite sheets, copper, steel sheets and polycarbonates.
“The two most popular types of material are metal and asphalt shingle. This is explained by their good value for money. They also look good, are quick to install and last a long time. Their application does not require a highly-trained specialists which also plays an important role,” says Yuri Gasanov, specialist at Tekhnonikol.
The cheapest type of hard roofing material is asbestos sheeting. Its advantages include its low cost and the fact that it can applied at any time of the year. However according to many market experts it does not have a very long service life. “Today we are seeing a lot more flat roofs for commercial real estate buildings. Usually angled roofs are used for their look and designers include them to make the building more uniquely attractive,” says Mr Sagalkov.
Sergey Sergeev, manager of the Hermitage Plaza project from Forum Properties comments, “Today you normally encounter the use of angled roofs in luxury village construction or in the central part of the city. Their usage normally relates to the importance of preserving a building’s architectural outline or helping a new building blend in well to its surroundings. The main advantage of angled roofs is their reliability since water and snow cannot build up. А значит и из строя она выходит существенно реже, чем плоская».”
Hard roofs are also easier to service. “There is always something which requires maintenance on the top of an industrial buildings: ventilators, air-cooling system, lighting, video cameras and other equipment. You can access a hard roof without worrying about damaging it. It is important however to install a safety rail and service personnel must undergo special safety training and be equipped with safety straps and safety lines,” says Alexandr Stuit, operations director at Step.
One of the primary disadvantages of angled roofs is that in the majority of cases they are impossible to service. As a result engineering equipment cannot be located on the roof but must be installed inside the building which reduces the amount of available space. Given the existing space shortages and the strictness of municipal regulations this is an ineffective and inadvisable option.

Roofing Materials for Flat Roofs
Despite their name flat roofs contain slopes to collect water. As you would expect the angles of are very small – from 2 – 7%. “Flat roofs can be divided into two types: service and non-service, that is to say from an engineering point of view. A roof can be used to locate and service bulky, essential engineering equipment like, air compressors, extraction fans, refrigeration systems etc thereby freeing up substantial areas within the building. The potential choice of surface covering is large and ranges from: concrete tiles in various colors and configurations with differing characteristics to specialized raised floors which can create a perfectly level surface and are similar in quality to a standard office floor,” says Mr Sergeev.
Usually flat roofs use soft roofing materials. These can be divided into several different types: polymer membranes, roll material, asphalt and asphalt mastic and materials based on liquid rubber.
The most widespreadly-used roofing material for flat roofs is roll materials. During the Soviet era virtually the only type of roofing material was ruberoid roofing felt. Today it is used rarely because of its short service life. It has been replaced by high tech materials made from modified asphalt which last for 20-25 years and function well in difficult weather conditions. Also in widespread use is roof membranes. Polymer membranes are durable and long-lasting with service lives of about 50 years which is four to five times longer than the best roll materials. Polymer membranes are also elastic and weather and frost-proof. Their large width also makes it possible to seal roofs of various complexity and configuration with a minimum number of seams.
The main disadvantage of roll materials is the risk of leaks at the seams and the need for constant maintenance. They can also fail if the sub-layer is not installed correctly. When snow and ice melts puddles form at the seams however it is often impossible to remove ice and snow because of the softness of roll covering. Special materials have been developed like mastic and liquid rubber which are particularly good at preventing leaks. Mastic comes in a sticky liquid which after application sets into a uniform layer. Its main advantage is an absence of seams. Another similar material is liquid rubber which forms into a single membrane which is completely impermeable to water, vapor and gas.
When it comes to servicing soft roof surfaces the situation is more complex since some of the materials puncture easily. “In order to avoid this you need to include an access bridge or platform. If, for example, you use a roof membrane then you need incorporate an access route for service personnel. Access routes are made from galvanized steel sheeting which is then coated with roof membrane in a different color in order to mark it out,” says Alexandr Stuit.

Inverted Roofing Systems
Today it is hard to imagine how someone came up with the idea of reversing the layers. The practice first emerged in Japan and the US. Today this technology is known as an inverted roofing system and it is widely-used in Russia. A very good example of an inverted roof is the Okhotny Ryad shopping center. The main advantage of inverted roofs is that a roll water-proofing layer is applied directly to the tiles followed by a heat insulating layer (a water vapor barrier is provided by the structure of the heat insulation layer). In order that the light insulating layer doesn’t come away or become damaged a layer of gravel or crushed rock is applied which performs the function of ballast and also levels the surface. The roof’s surface can then easily be incorporated into a flower garden or solarium or both as is often practiced in Japan. Effectively it is no longer a roof but an additional area.
“Today inverted roofs are regarded as more progressive since in comparison with traditional roofs they are lighter, easier to maintain and more reliable. However they must be kept in good condition. A build up of autumn leaves and city dirt can after a few seasons of neglect turn a once perfect inverted roof into a swimming pool,” comments Mr Sergeev.
Other advantages of inverted roofs include the fact that the upper covering is non-flammable and not prone to mechanical failure. However every cloud has a silver lining, “Finding a leak in an inverted roof is much more difficult since it is covered with gravel or sometimes even soil used to grow grass. This makes it extremely important to use premium class materials and highly-qualified specialists,” says Mr Gasanov.

Let There Be Light
Over the last few years transparent roofs have become very popular. They are made either from glass or multi-layered, shatter-proof plastic and mainly used for angled roofs. Plastic is very durable but it very quickly blurs and lets in less light than glass. Glass is currently the most expensive roofing material and also has some important drawbacks. For example, if the roof is not properly assembled it is very likely to have damp-proofing problems. It is crucial that special attention is paid to the structural integrity and strength characteristics of the roof. Snow must be constantly cleared away and it needs to be regularly cleaned and repaired.

The Cost
According to Mr Sergeev over the last six months the cost of roofing materials has increased considerably. “Half a year ago you could build a good, transparent, angled roof for $500/sqm and an easily serviceable concrete roof cost $110-170/sqm.” Mr Gasanov adds that cheaper materials made from oxidized asphalt cost about 40 rubles/sqm, polymer materials cost about 100 rubles/sqm and membranes from 250 rubles/sqm. It should be pointed out that asphalt materials are used in two layers so the cost has to be doubled. The cost of metal and asphalt roof shingle is about the same, ranging from 220-250 rubles/sqm and glass (plus supporting structure) costs from $250/300/sqm.