We think that today’s conversation will be interesting both for those who are just going to start building their own house in the spring, and for those who postponed its completion until spring, throwing temporary waterproofing, for example, roofing material, onto the rafters. After all, both the questions of the choice of roofing material and the device of the roof itself will still have to be solved. And we hope that today’s conversation will help both to avoid mistakes and miscalculations. No, we are not trying to pretend that we will give answers to all questions or give some kind of universal advice – perhaps not a single specialist can do this. But we will certainly try to give our readers objective information.
What determines the choice of roofing material and on whom?
In reality, all buildings can be divided into two types: frame and capital.
Frame – this is when the carrying function is performed in a certain way by the frame made of a thick bar or thick board (50-70 mm). In this case, the cavities between the frame elements are filled with some kind of effective insulation. Such structures of the frame type imply some kind of lightweight roofs. That is, the weight of the roofing material should be “light”, no more than 5 kg / m2. This group includes materials such as soft bituminous tiles, metal tiles, “Ondulin”, etc. We borrowed such designs from America – they just like light, pre-fabricated and relatively cheap designs that can be easily disassembled and recycled. There they, most likely, became fashionable even during the period of colonization of America by colonists from Europe. You didn’t like the building in any way – you disassembled and assembled another one in this place, partially using parts and parts removed from the old building. We need to move to another place – no problem either. Disassembled, took something with him, something (which can be obtained in a new place) “disposed of” immediately after disassembly.
In Europe, as a rule, more serious buildings are preferred. Apparently, this is also due to historical traditions. The buildings here are passed from generation to generation. From this calculation, as a rule, construction is carried out – the great-grandfather builds so that the great-grandchildren could live in the house he built. Naturally, this implies a different attitude than in America to construction and, accordingly, to the materials used in construction. In particular, the European tradition implies heavier roofing materials such as ceramic tiles. Such “heavy” roofing materials have a number of advantages over “light” ones – low thermal conductivity (and, consequently, energy saving), good noise insulation. And, of course, aesthetics, because piece material always looks much more expressive than sheet material. “Heavy” roofing materials, naturally, require a rafter system that is more serious in terms of its bearing capacity. Accordingly, a powerful rafter system must be supported by stronger walls. Well, stronger walls should rest, respectively, on a more powerful foundation..
Thus, the choice between “heavy” and “light” roofing materials must be made by the customer himself, proportioning his desires and material capabilities. And this choice must be taken into account and implemented when designing a house. After all, it is the project that should include a whole complex of interconnected technologically verified stages, starting from the study of soils in a specific area (location of groundwater, quicksands, soil quality), the quality of the foundation, the bearing capacity of the walls and ending with the rafter structure and the roof lying on it. That is, if at the design stage you have not incorporated the appropriate elements into the structure of the house, then you will not be able to make radical changes..
With “light” roofing materials, it is somewhat easier. If you have already chosen them, then you will still have the opportunity to replace one “light” material with another. But even here it cannot be said that you can easily make such a replacement. And here each of the materials assumes its own characteristics in the same truss structure, and replacing the material “on the fly” can entail very serious additional costs. So here, too, it is better to choose the material in advance and take this choice into account when designing. This is the surest way.
According to existing rules and regulations, any roofing structure must be calculated in such a way that, regardless of the weight of the roofing material itself (3 or 40 kg weighs per square meter), it withstands a load of 200 kg per square meter. The given figure for central Russia includes snow and wind loads and, of course, the corresponding safety factor.
Why are we talking about all this. It’s just that a lot of clients turn to us who are trying, if I may say so, to hop on a train that has already departed. All his life, a man cherished the dream of a beautiful expressive roof, he has already begun building a house. And when he came to us to buy a roof, he suddenly found out that a square meter of the roof itself weighs about 40 kg. Add to this the same 200 kg of snow and wind loads. When everything was calculated, it turned out that this person would have to part with his dream – neither the foundation, nor the walls, nor the rafters were designed for such a load. Of course he was very upset.
Of course, you can not listen to the figure we have named (200 kg / m2). This business, as they say, is the master’s. But here it is appropriate to recall the tale of the “three pigs”. Nif-Nif built both a house and a roof of straw in half a day, Nuf-Nuf weaved a structure from rods in a day, and Naf-Naf built the longest, but built a house of stone. How the construction of the straw and wicker houses from twigs ended, when the wolf came for the piglets, I think there is no need to remind. But the Wolf only imitated a strong wind load. Everything ended well with the third piglet and his house. He turned out to be reliably protected from all adversity: from physical, climatic and even moral damage. He just correctly took into account all the loads at the design stage. Apparently it was not in vain that he sang a song during the construction: “I, of course, are smarter than everyone. I build a house of stones.”.
Well, but seriously, you should never forget about this very figure. Customers very often naively believe that the lighter the roof, the less load on the rafter system and, consequently, on the walls and foundation, and the less problems with operation. When we start counting, it turns out that even with a small area of the house and the roof itself (only 50 m2), the customer has a 10-ton structure. And that’s not counting the weight of the roof and the weight of the rafters. The man is horrified. After all, he did not take these ten tons into account. And there is really nothing to be afraid of. With a well-designed project, competent accounting of all existing loads, an appropriate rafter system that evenly distributes the load on the walls, the structure of the house can easily withstand any load.
Let’s now go directly to the roofing materials themselves. Which each of them has advantages and disadvantages?
For a long time, it remains in our market, judging by the sales volume, perhaps the most popular roofing material. Why is this so? One of the reasons is that this material is very beneficial for builders in terms of the ratio of prices for installation and speed, as well as manufacturability of installation. After all, installation of a square meter of roofing a year ago costs almost $ 10. And what does it mean to lay one sheet of almost 6 square meters. Installation of such a sheet takes only a few minutes, even if you plant it on self-tapping screws (as expected), and not on nails (as is sometimes done). And those few minutes of work were estimated at almost $ 60. Now the prices for work have decreased slightly, but this work remains very profitable for builders. And who will refuse his own benefit?
Another reason for the popularity of metal tiles is that from a distance they very much resemble piece ceramic tiles. But only from afar.
In the west, it is mainly used as a roof covering for small structures, mainly for household purposes: gas stations, warehouses, outbuildings. In individual construction, it is used much less often than in Russia. We have a boom for this material. Perhaps this is due to the historical tendency of our consumer to metal roofs, or maybe just the consumer is always trying to choose a roof that requires minimal maintenance. And here they offer just a metal roof, and even similar to a natural tile. Apparently the combination of these qualities gave such a surge in popularity.
If you analyze the above table, then in terms of the ratio of advantages and disadvantages, the metal tile is much inferior to the ceramic tile. It has very low noise insulation, which, with the attic construction of the house (namely, such a construction is the most popular in our time, since it allows you not to lose a single meter of the useful volume of the building) makes you arrange more powerful noise and thermal insulation at the same time. After all, not many people like to fall asleep to the drumming of rain on the roof or the howl of the wind. The thermal conductivity of metal tiles is also high. Therefore, good insulation is simply vital. There is one more feature of this material that must be taken into account – this is the increased formation of condensation on the lower surface of the sheets (the dew point is located precisely on this surface). Condensation can cause, for example, a difference between day and night temperatures. Condensation is formed in such quantities that it must be discharged outside. But the fact that it is necessary to lay a waterproofing layer under a layer of metal tiles, both the customers themselves and the builders, as a rule, do not know or forget. The fact that the customer does not know about this is understandable, but builders are simply obliged to know and remember about this property of metal tiles. Installation of an additional layer of waterproofing, of course, will cause additional costs (~ $ 1 per square meter) and no one wants to bear these costs, but it helps to avoid many troubles during operation. As a rule, after a couple of months, builders come to us again and ask to remind them that they were told about waterproofing when they bought roofing material. It turns out that water just drips from the ceiling in the attic. Both the ceiling and the floor deteriorate, not to mention the furniture, and the rafter system slowly begins to rot. Naturally, the customer has material claims to the builders, and I must say they are quite reasonable.
Thus, the need for the correct combination of all functional technological layers of the roofing system is gradually becoming an alphabet for both builders and customers. That is, depending on the selected roofing material, there must be the right combination of all other components of the roofing system..
When fastening metal tiles, willy-nilly, it is necessary to break the surface protective layer. And once the protective layer is violated, then a potentially corrosive hazardous zone is created. In addition, large sheets always have a large linear expansion, therefore, with temperature fluctuations, there will be constant loosening of the fasteners. That is, the mounting holes will constantly expand. Over time, these expanding holes will have to be covered with some kind of mastic..
The modern market offers the buyer metal tiles coated with mineral granulate. Such a coating imitates natural piece tiles to the maximum extent. The same mineral granulate gives the metal tile maximum heat and sound insulation. But the price of metal tiles at the same time increases by about two times.
The copper roof has always stood apart due to its high cost (> $ 20 / m2). Nevertheless, many people like such a roof – over time, it oxidizes or becomes covered with a layer of the so-called patina. The patina color is brown with a greenish sheen. The advantages of this material include its high corrosion resistance, but this advantage is preserved only with full compliance with the installation rules. Violation of these rules, for example the presence of direct contact with iron or aluminum, accelerates corrosion so much that it negates all the benefits. This phenomenon occurs, for example, when using steel nails when installing a roof or installing a Velux skylight not with a copper but with an aluminum frame. Disadvantages in terms of the formation of condensate on the inner surface of the roof (which is associated with even higher thermal conductivity than steel), this material has the same as metal tiles, so we will not dwell on them separately.
The disadvantages of all metal roofs, without exception, must be attributed to the fact that they have the ability to accumulate static and atmospheric electricity. In this regard, there is an urgent need to equip metal roofs with a lightning protection system..
Soft roofing materials
There are two main supplying countries: Finland and the USA. “Shingles” enters our market from America – it has a rectangular shape of teeth – the assembled roof resembles brickwork. Materials from Finland are usually hexagonal in the form of teeth – the assembled roof resembles a honeycomb. The most famous is “Katepal”, slightly less famous is “Ikopal”. This material is somewhat reminiscent of the roofing material, which is familiar to the Russian consumer. It is a fiberglass, impregnated with rubber bitumen and covered with a special powder – stone chips, etc. In general, the powder material depends on the country of origin. The purpose of the powder is to prevent fading, the damaging effects of ultraviolet radiation and mechanical abrasive effects. And so that a spark from a fire from a neighboring site, accidentally flying onto your roof, could not cause absolutely any harm to it. Of this type of roofing, it is worth highlighting the Katrili series from the Katepala range. It stands out against the background of other materials with a higher quality design, provided by color halftone transitions.
First of all, it is necessary to imagine the technology of laying these materials. They should be based on a flat wooden surface. Best of all, if it is a multi-layer moisture-resistant plywood. You can also use edge-to-edge edged board. And here it is also necessary to very carefully approach the creation of a puff cake (roof – ventilation layer – waterproofing – insulation). Some companies complete roof tiles with additional ventilation elements (flat, in the form of pipes, etc.)
The undoubted advantages of these materials are the relative ease of installation and a very small amount of waste when laying on a complex roof, as well as fire resistance and excellent sound insulation. Why is there practically no waste? Because almost every cut is used. When moving from one plane to another, I cut off the strip – with trimming and began laying the next row. The disadvantages are the possibility of deformation of individual “petals” in strong winds, but this occurs mainly as a result of violation of installation rules.
We still have one more “light” roofing material – “Ondulin”. But before we move on to discuss it, I would like to ask a question.
There is information that Ondulin was originally intended to cover some temporary outbuildings such as sheds, hangars, etc. Is it really?
If you look at the brochures and videos, you can make exactly this conclusion. “Ondulin” was indeed originally intended for light buildings. What is this material? It is pressed board impregnated with bitumen under pressure and painted in an attractive color. It has a number of positive factors. First of all, it is suitable for those who are on a tight budget and at the same time are able to tackle the problem of installing a new roof using the DIY method. The material is light, therefore, it can be transported from warehouse to construction site even on the trunk of your own car. It is lightweight, and transporting it from the ground to the roof will not cause difficulties. (Even a woman or a teenager can easily tie the sheet underneath and send it upward, but upstairs one man can handle it. Thus, you don’t have to invite any helpers for installation – you can do it with your own family.) No special cutting equipment is required. sheets. “Ondulin” is completed with all the necessary additional elements: skates, valleys, special colored roofing nails, pediment elements, etc. Ventilation outlets, hatches, etc. are also sold, however, in most cases (with a simple roof shape) they are not used, preferring to bring the ventilation gap under the roof ridge.
Its area of application is small buildings: bungalows, sheds, garages or agricultural buildings. But, first of all, this is a niche of small buildings – up to 100-120 m2 of roofing. You should not be afraid to use material for the construction of residential buildings (mainly summer ones and, as we said, a small area). The material is certified, the manufacturer gives it a 15-year insurance guarantee, of course, subject to the technology of its installation. In this case, the real life of its service is called – up to 50 years. And this is taking into account our climatic conditions.
The combination of all these factors makes Ondulin undoubtedly attractive.
Based on what considerations you need to choose a roofing material, and how a Russian buyer usually does it?
It should be noted that the Russian buyer is mostly a conservative – not all new materials entering the domestic market immediately win sympathy and take root. In the case of metal tiles, it cannot be said that it immediately became the queen of roofs. She won her popularity far from immediately. Soft roofs such as “Katepal” were also looking for their buyer for a long time. And every year this material is gradually expanding its consumer niche, winning back sales from the same metal tile..
There is simply no perfect or universal material. For some, the price decides everything, for others this factor is not decisive. If the price is the decisive factor, then the rest of the properties, such as aesthetics, noise insulation, heat saving, seem to fade into the background. The buyer simply ignores them (well, a person has little money, but the roof needs to be covered – there is no time for aesthetics). Another seeks to get a lot of positive consumer qualities, and the price does not bother him much (in fact, of course, there are no people who do not care about the price). The third chooses a roof that none of the neighbors has. The fourth, on the contrary, wants to select only such material that would correspond to both the neighbor on the right and the neighbor on the left. When a person builds without a project, and even in a hurry, because he does not want to pay for a “simple” team of “shabashniks” hired by him, then most often the choice of material is influenced by the convenience of acquisition, affordable price and ease of installation. But this is when it comes to small buildings. Those who build large objects, for example, homes for permanent residence, as a rule, choose the material long and carefully..
Based on the foregoing, there is only one advice on choosing a roofing material. Weigh carefully all the “pros” and “cons”, taking into account at least the materials that we have given in this review. Select a defining criterion (or a combination of criteria): quality, price, appearance, etc. and try to balance the conclusions drawn from the reading and the determining criterion (s). Based on this balance and make your choice.
Does each of the materials listed in this review bring some of its own characteristics to the roof structure?
Features are expressed in the ratio of the parameters of the rafter structure. For heavy roofs, the cross-section of the rafters should be larger and the pitch of the rafters should be more frequent (the minimum size of the rafters is 70×150 mm with the minimum pitch). For lighter materials, the frequency of the rafters can be much less, and the cross-section of the rafters themselves is less. A beam of 50×150 mm can be used here with a rafter pitch of up to 1 meter.
The increased consumption of sawn timber for a truss structure for natural tiles is one of the factors that hinder its widespread use..
As you know, roofs are flat and pitched. For flat roofs, there is a huge market for roofing materials – mainly mastic or weldable materials. But we will not talk about them today. Pitched roofs are roofs that slope from 10 to 90 degrees. In our region, the most common tilt angles lie in the range from 20 to 45 degrees. Taking into account the peculiarities of the selected roofing material (see table), the angle of inclination of the roof must be chosen so that, firstly, the snow does not accumulate on the roof, and secondly, it does not come off the roof like an avalanche. After all, an avalanche snowfall brings a lot of trouble – it breaks drain gutters and downpipes, etc..
And there are some general points that must be taken into account when organizing any roofing structure, regardless of the chosen roofing material?
Even when using roofing materials with low thermal conductivity, such as ceramic tiles, “Ondulin”, etc., condensation still forms under them, even in minimal amounts compared to metal roofs. And this condensate must either fall onto the waterproofing layer and flow down through it to the cornice, or part of it must be carried out by circulating air currents, which must pass freely in the under-roof space. Therefore, waterproofing must be laid along the rafters. Its purpose is to prevent the rafter structure itself from getting wet by condensate or wind-blown moisture and the layer of insulation located between the rafters. After all, such widespread heaters as “Isover” and “Ursa” simply lose their heat-insulating properties when wet and are mechanically deformed under the influence of moisture. As a result, gaps are formed between the insulation and the rafters, through which the heat is simply blown out into the street. In this regard, more expensive basalt-based insulation materials such as Rockwell and Park behave much better. They are much less afraid of water, but they are much more expensive. There must be a double batten between the roofing material and the waterproofing layer. The counter-lathing is a bar with a section of 30×50 mm, located along the rafters. Lathing – with a step of the material itself (in the wavelength of the tile) is located across the counter-lathing. Thus, the task of the counter-batten is to raise the roofing material for ventilation of the under-roof space.
Based on materials from the “Repair and Construction” magazine