- How durable popular roofing materials are
- How to choose durable shingles
- Metal tile service life
- Performance characteristics of natural tiles
- Other types of roofing
The next and such a long-awaited spring season means not only the end of cold weather, but also the need to check the condition of roofing materials. How many years have passed the roofing of your house this year – isn’t it time to repair it in places, and possibly replace it completely? The service life of any roof covering, be it metal or natural tiles, depends on a number of quality characteristics inherent in each of the roofing materials. Consider what characteristics and how they affect the service life of a particular roof.
How durable popular roofing materials are
During its service life, any roof covering is exposed to atmospheric precipitation, multidirectional wind, ultraviolet light, temperature extremes, the influence of microorganisms and insects, as well as various mechanical loads. Manufacturers usually declare the following guarantees for their products: from 15 to 25 years for soft tiles; from 5 to 15 years for metal tiles; from 20 to 50 years for natural (ceramic) tiles. Moreover, each manufacturer declares that his products will last much longer than the warranty period named by him – at least three times, and the service life of natural tiles will in no way be less than 100 years. In fact, the service life of the roofing material directly depends on the quality of manufacture. Consider the quality characteristics of the roofing material in more detail.
How to choose durable shingles
When choosing, special attention should be paid to resistance to high and low temperatures – how much this tile is able to maintain its shape at high and low temperatures. Flexible shingles are based on polyester or non-woven fiberglass, most often impregnated with modified bitumen, and it is the polymer modifier additive that is the most important and decisive component in how effectively this roofing will withstand temperature extremes. The most popular bitumen modifiers are atactic polypropylene (APP) and styrene-butadiene-styrene (SBS) – the first of them is more resistant to heat (withstands up to 140 ° C), the second is less stable (up to 100 ° C), but more frost-resistant. In the temperate climate of Russia, shingles, the bitumen of which is modified by SBS, will last longer and precisely because of its frost-resistant qualities.
An important criterion for the quality of shingles will be its resistance to ultraviolet radiation. UV resistance depends on three factors:
- The presence of a polymer additive in the composition of bitumen – unmodified bitumen is much less resistant to solar ultraviolet light;
- The density of basalt or mineral chips applied to the outer (outer) side of the flexible tile – its particles reliably protect the bitumen impregnation from direct contact with sunlight;
- How good is the adhesion (adhesion) of the particles of stone chips to bitumen – if manufacturers violate the technical conditions of production, this adhesion will be insufficient, there will be an early loss of chips from significant areas of flexible tiles, exposing the bitumen layer to the sun’s rays.
The reverse (lower) side of the shingles is covered with a self-adhesive rubber-bitumen composition completely or in the form of a strip – when the roof formed by the shingles is heated by the sun’s rays, the rubber-bitumen layer must firmly connect each shingle with those located nearby, thereby increasing the tightness of the roof. The larger the area of the self-adhesive layer in relation to the face of the shingle, the higher the adhesion strength, which means that the service life of such a roof will be long. The minimum area of the rubber-bitumen strip is 15% of the area of the front side of the shingle.
Flexible shingles of the world’s largest manufacturers are distinguished by a larger area of the adhesive layer – more than 50% of the shingle area. The area of the adhesive layer determines the service life of the entire bituminous tile covering, not just one shingle.
Not unimportant will be the strength of the base of the shingles, on which the resistance to tearing depends. This is especially important for areas in valleys, where the roof covering will experience the greatest pressure of snow and water – the strength of a flexible roof laid in them should be especially high.
Metal tile service life
The durability of the steel profiled sheet with zinc and polymer layers applied on top depends on the thickness of the original steel sheet, the zinc layer and the type of polymer coating. The steel sheet used for the production of metal tiles usually has a thickness of 0.45 to 0.8 mm – thicker steel is difficult to profile, while thin steel will easily deform both during installation and during its operational life. However, even with a steel thickness of more than 0.55 mm, the rigidity is excessively high, therefore, such a metal tile often has a somewhat distorted geometry, after its installation on the roof, the joints between adjacent sheets are clearly visible.
The thickness of the zinc layer, which protects the steel from corrosion, especially affects the service life of the metal tile – the higher it is, the better. But galvanizing alone will not be enough – both sides of the steel sheet with a zinc layer applied to them must be passaged and covered with a primer layer that protects the zinc layer from air oxidation.
The type of polymer used to create a metal tile affects both the service life and the preservation of its color from fading under the sun. Plastisol, largely due to the layer thickness of 200 microns, is resistant to mechanical damage and, accordingly, resists atmospheric corrosion well, but is weakly resistant to ultraviolet light and loses its protective properties at temperatures above +60 ° C. Polyester perfectly resists high temperatures up to 120 ° C, effectively protects metal tiles from ultraviolet radiation and corrosion, but its mechanical strength is not high, because maximum application thickness does not exceed 30 microns. The polymer layer of polyvinyl fluoride acryl (PVF2) is resistant to ultraviolet rays and temperature extremes (from high to +120 ° C, to low -60 ° C), however, it is applied with a layer of no more than 27 microns – stronger than polyester, but less resistant to mechanical damage than plastisol. Pural acts as a kind of compromise among the polymers used to protect metal tiles – with the same resistance to high and low temperatures, ultraviolet and corrosion, its layer of 50 microns provides good mechanical strength.
In addition to the usual galvanized metal tile, there is profiled steel protected from corrosion by a layer of aluzinc – an alloy consisting of aluminum (55%), zinc (43.5%) and silicon (1.5%). The aluzinc coating provides the steel sheet with 4 times more corrosion protection than galvanizing. In addition, the aluzinc layer has high resistance to high atmospheric temperatures, which significantly increases the service life of the metal roofing.
In the case of metal tiles, lined from the outside with mineral chips on a polymer binder, the service life depends precisely on the quality characteristics of the polymer.
In many ways, the service life of a roof made of metal tiles depends on the quality of self-tapping screws and polymer washers on them – cheap self-tapping screws lose the galvanized layer over time and rust, low-quality polymer washers dry out and lose their function of sealing the holes through which a sheet of metal tile is attached with screws.
Performance characteristics of natural tiles
The main criterion on which the long service life of cement-sand and ceramic tiles is based is frost resistance. And this indicator depends on the porosity and density, which determine the degree of moisture absorption of the tiles. Ideally, natural tiles should absorb no more than 7% of moisture from their mass, i.e. the porosity of its structure should be lower and the density higher. With the onset of the cold season, excessively porous tiles absorb moisture, expanding when freezing and causing damage to its structure of various nature – from the smallest to significant, and with each new cold season, the amount and depth of damage only increases. To summarize – the lower the porosity of natural tiles, the longer their service life will be..
Tests for frost resistance of cement-sand and ceramic tiles are carried out in the laboratory as follows: samples of natural tiles are immersed in warm water (at t + 20 ° C); they are removed from warm water and immediately placed in a freezer (at t -20 ° C) for two hours; removed from the freezer and placed back in warm water; then everything is repeated again. Immersion of tiles in warm water, followed by freezing and thawing is called “one cycle”. According to the requirements of European technical specifications, natural tiles of any brand must withstand at least 150 such cycles – the products of the largest tile manufacturers in Europe are capable of withstanding 1,000 such cycles, while they will not receive any visible damage. It should be noted that under actual operating conditions, a tiled roof will never withstand such extreme temperature conditions..
In addition to being resistant to temperature extremes, natural tiles must be resistant to solar ultraviolet radiation and bending strength. Modern technologies for the production of roofing ceramics ensure color retention for a significant period of operation, which is up to strength – one tile of cement-sand and ceramic tiles of a number of well-known brands is capable of withstanding a weight of 250 kg.
Other types of roofing
Porcelain tiles – in comparison with natural tiles, they are more frost-resistant, because has a significantly smaller number of pores and, accordingly, significantly less moisture absorption. The technology for the production of roofing porcelain stoneware includes two special stages: firing the molded mixture at a temperature of about 1,300 ° C, fusing the internal structure of the tile; impact on the fired raw material of the press, which develops a pressure of 800 kg per cm2. The result is a low moisture absorption of porcelain tiles (0.1%) and, accordingly, excellent frost resistance.
Resistance to fading under ultraviolet radiation of porcelain stoneware is provided by painting in bulk with the introduction of pigments, which include salts of chromium, cobalt and zirconium. The mechanical strength of porcelain tiles deserves special attention – the products of some manufacturers are able to successfully withstand 65 MPa for bending.
Among all the types of roofing described above, this material is undoubtedly the leader – its performance characteristics have been tested over many centuries. We are talking about copper, for which a period of 200 years, and without any repair work, is not the limit at all. The roof made of non-ferrous metal does not corrode in any way, and the greenish patina that covers the copper sheets over time or under the influence of a special technology only strengthens their structure.