Roof Hail Storm Damage

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Collin County Hail Storm Damage to Roofs caused by Hazards include 60 mph wind gusts and half dollar size hail. Hail damage to vehicles roofs and skylights, expect wind damage to roofing, siding, and trees. locations impacted heaviest with hail and wind damage in Collin county include, mckinney, bonham, anna, princeton, farmersville, leonard, lowry crossing, honey grove, wolfe city, celeste, dodd city, bailey, bonham state park, melissa, blue ridge, trenton, new hope, ladonia, weston and pecan gap. Roof Hail Storm Damage [2ndkey]


21968284 – man with flip-flops standing on the grass with hails after hailstorm

Collin County & north central texas storm damage roofs. Roof tarping will help prevent leaking roof into the attic area until the roof can be fully replaced. Asphalt and Composition Shingles Hail Damage Random damage with no discernable pattern. Hail hits that are black in color. Loss of granules, which may expose the roof felt. Asphalt and/or mat that appears shiny. Hail hits that are soft to the touch, like the bruise on an apple. Roof Hail Storm Damage [2ndkey] Less than 1 inch: When smaller than an inch, or about the size of a quarter, hail can inflict damage to asphalt roofing. Greater than 2 inches: Any hail greater than 2 inches will almost always cause some level of hail damage to an asphalt roof. A roof is part of a building envelope. It is the covering on the uppermost part of a building or shelter which provides protection from animals and weather, notably rain or snow, but also heat, wind and sunlight. The word also denotes the framing or structure which supports that covering. Tallent Roofing Inc The characteristics of a roof are dependent upon the purpose of the building that it covers, the available roofing materials and the local traditions of construction and wider concepts of architectural design and practice and may also be governed by local or national legislation. Roof Hail Storm Damage [2ndkey] In most countries a roof protects primarily against rain. A verandah may be roofed with material that protects against sunlight but admits the other elements. The roof of a garden conservatory protects plants from cold, wind, and rain, but admits light. Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc An asphalt shingle is a type of wall or roof shingle that uses asphalt for waterproofing. It is one of the most widely used roofing covers in North America because it has a relatively inexpensive up-front cost and is fairly simple to install. Roof Hail Storm Damage [2ndkey] Roofing repair from Texas storm hail damaged roofs. Re Roofing Service, Roof Companies, Gutter Repair, Roof Repair, New Roof Estimates, Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc Types of Roofing Shingles, different types of shingles provide different levels of protection and warranty against inciement weather. Most brands are guaranteed to resist straight line wind roof damage and hail damage roof. Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc A ridge cap on a 3-tab asphalt shingle roof is composed of individual shingle “tabs” folded over the ridge and nailed partially overlapping one-another An asphalt shingle is a type of wall or roof shingle that uses asphalt for waterproofing. It is one of the most widely used roofing covers in North America because it has a relatively inexpensive up-front cost and is fairly simple to install. Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc Qualities Of Asphalt Shingles Asphalt shingles have varying qualities which help them survive wind, hail, or fire damage and discoloration. * The American Society of Testing Materials (ASTM) has developed specifications for roof shingles: ASTM D 225-86 (Asphalt Shingles (Organic Felt) Surfaced with Mineral Granules) and ASTM D3462-87 (Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules), ASTM D3161, Standard Test Method for Wind-Resistance of Asphalt Shingles (2005), Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc * Many shapes and textures of asphalt shingles are available: 3 tab, jet, “signature cut”, Art-Loc, t-lock, tie lock, etc. Architectural (laminated) shingles are a multi-layer, laminated shingle which gives more varied, contoured visual effect to a roof surface and add more resistance for water. These shingles are designed to avoid repetitive patterns in the shingle appearance. Hip and ridge lines can have either standard 3-tab shingles cut to fit. Manufacturers also make specialized shingles for these areas. Roof Hail Storm Damage [2ndkey] Starter shingles are also required and, because they are not visible after installation is complete, the use of extra shingles (commonly referred to as ‘waste’) are used here. However, manufacturers also make a specialized starter row shingle. The use of specialized ridge/hip shingles and the use of specialized starter row shingles, results in decreased labor expenses in exchange for an increase in material cost. Laminated shingles are heavier and more durable than traditional 3-tab shingle designs. Roof Hail Storm Damage [2ndkey] * Solar reflecting shingles help reduce air conditioning costs in hot climates by being a better reflective surface. * Wind damage: Asphalt shingles come in varying resistance to wind damage. Shingles with the highest fastener pull through resistance, bond strength of the self seal adhesive, properly nailed will resist wind damage the best. Extra precautions can be taken in high wind areas to fasten a durable underlayment and/or seal the plywood seams in the event the shingles are blown off.  Roof Hail Storm Damage [2ndkey] UL 997 Wind Resistance of Prepared Roof Covering Materials class 1 is best Wind Resistance roof standard and ASTM D 3161 class F is best for bond strength. * Hail damage: Hail storms in Texas can damage asphalt shingles. For impact resistance UL 2218 Class 4 is best. This increases survivability from hail storms but the shingles become more susceptible to hail damage with age. * Fire resistance: Forest fires and other exterior fires risk roofs catching on fire. Fiberglass shingles have a better, class A, flame spread rating based on UL 790, and ASTM E 108 testing. Organic shingles have a class C rating. Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc * Algae resistance Algae is not believed to damage asphalt shingles but it may be objectionable aesthetically. Different treatment methods are used to prevent discoloration from algae growth on the roof. Moss feeds on algae and any other debris on the roof. Some manufactures offer a 5- to 10-year warranty against algae growth on their algae resistant shingles. Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc * Locking shingles: Special asphalt shingles are designed to lock together called tie lock or T lock. * Durability Shingle durability is ranked by warranted life, ranging from 20 years to lifetime warranties are available. However a stated warranty is not a guarantee of durability. A shingle manufacturer’s warrantie may pro-rate repair costs, cover materials only, have different warranty periods for different types of damage, and transfer to another owner. Roof Hail Storm Damage [2ndkey] Tallent Roofing Inc about ASHALT SHINGLES Shingles tend to last longer where the weather stays consistent, either consistently warm, or consistently cool. Thermal shock can damage shingles, when the ambient temperature changes dramatically within a very short period of time. Roof Hail Storm Damage [2ndkey] “Experiments…have noted that the greatest cause of asphalt shingle aging is thermal loading.” Over time the asphalt becomes oxidized and becomes brittle. Roof orientation and ventilation can extend the service life of a roof by reducing temperatures. Shingles should not be applied when temperatures are below 10 °C (50 °F), as each shingle must seal to the layer below it to form a monolithic structure. The underlying exposed asphalt must be softened by sunlight and heat to form a proper bond.   Left: Example of faster asphalt shingle wear along eaves due to channeled water running down the roof. Right: Severe shrinkage resulting in tearing away of entire flaps. Water running down the roof can seep around the exposed nails into the interior space. The protective nature of asphalt shingles primarily comes from the long-chain hydrocarbons impregnating the paper. Over time in the hot sun, the hydrocarbons soften and when rain falls the hydrocarbons are gradually washed out of the shingles and down onto the ground. Along eaves and complex rooflines more water is channeled so in these areas the loss occurs more quickly. Eventually the loss of the heavy oils causes the fibers to shrink, exposing the nail heads under the shingle flaps. The shrinkage also breaks up the surface coating of sand adhered to the surface of the paper, and eventually causes the paper to begin to tear itself apart. Once the nail heads are exposed, water running down the roof can seep into the building around the nail shank, resulting in rotting of roof building materials and causing moisture damage to ceilings and paint inside. HAIL DAMAGE ROOF Hail is a form of solid precipitation. It is distinct from ice pellets (American sleet), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets (American sleet) fall generally in cold weather while hail growth is greatly inhibited during cold surface temperatures Hail can cause serious damage, notably to automobiles, aircraft, skylights, glass-roofed structures, livestock, and most commonly, farmers’ crops.  Hail damage to roofs often goes unnoticed until further structural damage is seen, such as leaks or cracks. It is hardest to recognize hail damage on shingled roofs and flat roofs, but all roofs have their own hail damage detection problems. Metal roofs are fairly resistant to hail damage, but may accumulate cosmetic damage in the form of dents and damaged coatings. Hail is one of the most significant thunderstorm hazards to aircraft. When hailstones exceed 0.5 inches (13 mm) in diameter, planes can be seriously damaged within seconds. The hailstones accumulating on the ground can also be hazardous to landing aircraft. Hail is also a common nuisance to drivers of automobiles, severely denting the vehicle and cracking or even shattering windshields and windows. Wheat, corn, soybeans, and tobacco are the most sensitive crops to hail damage. Hail is one of Canada’s most expensive hazards. Rarely, massive hailstones have been known to cause concussions or fatal head trauma. Hailstorms have been the cause of costly and deadly events throughout history. One of the earliest known incidents occurred around the 9th century in Roopkund, Uttarakhand, India, where 200 to 600 nomads seem to have died of injuries from hail the size of cricket balls. The largest hailstone in terms of diameter and weight ever recorded in the United States fell on July 23, 2010 in Vivian, South Dakota; it measured 8 inches (20 cm) in diameter and 18.62 inches (47.3 cm) in circumference, weighing in at 1.93 pounds (0.88 kg). This broke the previous record for diameter set by a hailstone 7 inches diameter and 18.74 inches circumference (still the greatest circumference hailstone) which fell in Aurora, Nebraska in the United States on June 22, 2003, as well as the record for weight, set by a hailstone of 1.67 pounds (0.76 kg) that fell in Coffeyville, Kansas in 1970 FLAT ROOF TPO MATERIALS A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof. Flat roofs, or “low-slope” roofs, are also commonly found on commercial buildings throughout the world. The National Roofing Contractors Association defines a low-slope roof as having a slope of 3-in-12 or less Flat roofs Flat roofs exist all over the world and each area has its own tradition or preference for materials used.Roof Hail Storm Damage [2ndkey] In warmer climates, where there is less rainfall and freezing is unlikely to occur, many flat roofs are simply built of masonry or concrete and this is good at keeping out the heat of the sun and cheap and easy to build where timber is not readily available. In areas where the roof could become saturated by rain and leak, or where water soaked into the brickwork could freeze to ice and thus lead to ‘blowing’ (breaking up of the mortar/brickwork/concrete by the expansion of ice as it forms) these roofs are not suitable. Flat roofs are characteristic of the Egyptian, Persian, and Arabian styles of architecture. In such areas, single-ply roofing is one of the best roofing options as single-ply membrane is best suited for all types of weather. Construction methods Any sheet of material used to cover a flat or low-pitched roof is usually known as a membrane and the primary purpose of these membranes is to waterproof the roof area. Materials that cover flat roofs typically allow the water to run off from a slight inclination or camber into a gutter system. Water from some flat roofs such as on garden sheds sometimes flows freely off the edge of a roof, though gutter systems are of advantage in keeping both walls and foundations dry. Gutters on smaller roofs often lead water directly onto the ground, or better, into a specially made soakaway. Gutters on larger roofs usually lead water into the rainwater drainage system of any built up area. Occasionally, however, flat roofs are designed to collect water in a pool, usually for aesthetic purposes, or for rainwater buffering. Traditionally most flat roofs in the western world make use of tar or asphalt more usually felt paper applied over roof decking to keep a building watertight. The felt paper is in turn covered with a flood coat of bitumen (asphalt or tar) and then gravel to keep the sun’s heat, UV rays and weather off it and helps protect it from cracking or blistering and degradation. Roof decking is usually of plywood, chipboard or OSB boards (OSB = Oriented Strand Board, also known as Sterling board) of around 18mm thickness, steel or concrete. The mopping of bitumen is applied in two or more coats (usually 3 or 4) as a hot liquid, heated in a kettle. A flooded coat of bitumen is applied over the felts and gravel is embedded in the hot bitumen. A main reason for failure of these traditional roofs is ignorance or lack of maintenance where people or events cause the gravel to be moved or removed from the roof membrane, commonly called a built-up roof, thus exposing it to weather and sun. Cracking and blistering occurs and eventually water gets in. Roofing felts are usually a ‘paper’ or fiber material impregnated in bitumen. As gravel cannot protect tarpaper surfaces where they rise vertically from the roof such as on parapet walls or upstands, the felts are usually coated with bitumen and protected by sheet metal flashings. In some microclimates or shaded areas these rather ‘basic’ felt roofs can last well in relation to the cost of materials purchase and cost of laying them, however the cost of modern membranes such as EPDM has come down over recent years to make them more and more affordable. There are now firms supplying modern alternatives. If a leak does occur on a flat roof, damage often goes unnoticed for considerable time as water penetrates and soaks the decking and any insulation and/or structure beneath. This can lead to expensive damage from the rot which often develops and if left can weaken the roof structure. There are health risks to people and animals breathing the mould spores: the severity of this health risk remains a debated point. While the insulation is wet, the “R” value is essentially destroyed. If dealing with an organic insulation, the most common solution is removing and replacing the damaged area. If the problem is detected early enough, the insulation may be saved by repairing the leak, but if it has progressed to creating a sunken area, it may be too late. One problem with maintaining flat roofs is that if water does penetrate the barrier covering (be it traditional or a modern membrane), it can travel a long way before causing visible damage or leaking into a building where it can be seen. Thus, it is not easy to find the source of the leak in order to repair it. Once underlying roof decking is soaked, it often sags, creating more room for water to accumulate and further worsening the problem. Another common reason for failure of flat roofs is lack of drain maintenance where gravel, leaves and debris block water outlets (be they spigots, drains, downpipes or gutters). This causes a pressure head of water (the deeper the water, the greater the pressure) which can force more water into the smallest hole or crack. In colder climates, puddling water can freeze, breaking up the roof surface as the ice expands. It is therefore important to maintain your flat roof to avoid excessive repair. An important consideration in tarred flat roof quality is knowing that the common term ‘tar’ applies to rather different products: tar or pitch (which is derived from wood resins), coal tar, asphalt and bitumen. Some of these products appear to have been interchanged in their use and are sometimes used inappropriately, as each has different characteristics, for example whether or not the product can soak into wood, its anti-fungal properties and its reaction to exposure to sun, weather, and varying temperatures. Modern flat roofs can use single large factory-made sheets such as EPDM synthetic rubber, PVC (polyvinyl chloride), TPO (thermplastic polyolefin) etc. Although usually of excellent quality, one-piece membranes are called single plies are used today on many large commercial buildings. Modified bitumen mebranes which are widely available in one metre widths are bonded together in either hot or cold seaming processes during the fitting process, where labour skill and training play a large part in determining the quality of roof protection attained. Reasons for not using one-piece membranes include practicality and cost: on all but the smallest of roofs it can be difficult to lift a huge and heavy membrane (a crane or lift is required) and if there is any wind at all it can be difficult to control and bond the membrane smoothly and properly to the roof. Detailing of these systems also plays a part in success or failure: In some systems ready-made details (such as internal and external corners, through-roof pipe flashings, cable or skylight flashings etc.) are available from the membrane manufacturer and can be well bonded to the main sheet, whereas with materials such as tar papers this is usually not the case – a fitter has to construct these shapes on-site. Success depends largely on their levels of skill, enthusiasm and training – results can vary hugely. Metals are also used for flat roofs: lead (welded or folded-seamed), tin (folded, soldered or folded-seamed) or copper. These are often expensive options and vulnerable to being stolen and sold as scrap metal. Flat roofs tend to be sensitive to human traffic. Anything which produces a crack or puncture in the waterproofing membrane can quite readily lead to leaks. Flat roofs can fail, for example; when subsequent work is carried out on the roof, when new through-roof service pipes/cables are installed or when plant such as air conditioning units are installed. A good roofer should be called to make sure the roof is left properly watertight before it is left. In trafficked areas, proper advisory/warning signs should be put up and walkways of rubber matting, wooden or plastic duck-boarding etc. should be installed to protect the roof membrane. On some membranes, even stone or concrete paving can be fitted. For one-off works, old carpet or smooth wooden planks for workers to walk or stand on will usually provide reasonable protection. Traditionally the smelly, hot, physically demanding and sometimes dangerous work of tarring flat roofs has often meant that uneducated fitters of doubtful reputation have done work to a poor standard: This together with a lack of regular inspection and maintenance has meant that flat roofs have a poor reputation and there is an unwillingness to retain or to build them, which is unfortunate, given the potential usefulness of flat areas, the more so with the excellent performance of modern membranes, many of which come with long warranties and provide an excellent roof covering. Protected Membrane Roof A protected membrane roof is a roof where thermal insulation or another material is located above the waterproofing membrane. Modern green roofs are a type of protected membrane roof. This development has been made possible by the creation of waterproofing membrane materials that are tolerant of supporting a load and the creation of thermal insulation that is not easily damaged by water. Frequently, rigid panels made of extruded polystyrene are used in PMR construction. The chief benefit of PMR roof design is that the covering protects the waterproofing membrane from thermal shock, ultraviolet light and mechanical damage. One potential disadvantage of protected membrane roof construction is the need for structural strength to support the weight of ballast that prevents wind from moving rigid foam panels or the weight of plants and growth media for a green roof. However, when flat roofs are constructed in temperate climates, the need to support snow loadmakes additional structural strength a common consideration in any event. ROOF PITCH Roof pitch The pitch of a roof is its vertical rise divided by its horizontal span (or “run”), what is called “slope” in geometry and stair construction, or the tangent function in trigonometry. In the imperial measurement systems it is typically expressed with the rise first and run second. In the USA, the run is denominated by the number 12, giving a ratio of how many inches of rise or fall there are to each 12 inches (one foot) of run. For example, 3:12, 4:12, 5:12, and so on. Countries which use metric measurement systems use a degree angle, or what fall there is per unit of run, and expressed as a “1 in x” slope, a 1 in 1 slope being 45°. Where convenient, the least common multiple is used, e.g. a 3 in 4 slope, rather than “9 in 12” or “1 in 1 1/3”. The pitch matters for a variety of reasons including the type of roofing material used, walkability, proportions to the building as a whole which is sometimes a critical factor in some architectural styles such as a steep pitch in Gothic architecture and a low pitch in Classical architecture, and combinations of pitches form distinctive roof shapes such as a gambrel roof. The basic ranges of pitch are not uniformly defined but range from flat, which are not perfectly flat but sloped to drain water up to 1/2:12 to 2:12 ( 1 in 24 to 1 in 6); low-slope roofing requires special materials and techniques to avoid leaks and ranges from 1:12 (2:12) to 4:12 (1 in 3); conventional from 4:12 (1 in 3) to 9:12 (3 in 4); and steep-slope roofing is above 9:12 (3 in 4)(21:12) (7 in 4) and may require extra fasteners. US convention is to use whole numbers when even (e.g. “three in twelve”) or the nearest single or two-digit fraction when not (e.g. either “five and a quarter in twelve” or “five point two-five in twelve”, each expressed numerically as 5.25:12). Definitions vary on when a roof is considered pitched. In degrees, 10° (2 in 12 or 1 in 6) is considered a minimum. The exact roof slope in degrees is given by the arctangent. For example: arctan(3/12)=14.0° The primary purpose of pitching a roof is to redirect water and snow. Thus, pitch is typically greater in areas of high rain or snowfall. The steep roof of the tropical Papua New Guinea longhouse, for example, sweeps almost to the ground. The high, steeply-pitched gabled roofs of northern Europe are typical in regions of heavy snowfall. In some areas building codes require a minimum slope. Buffalo, New York and Montreal, Quebec, Canada, specify 6 in 12, a pitch of approximately 26.6 degrees. Carpenters frame rafters on an angle to “pitch” a roof. Gable and other multi-pitched roofs allow for lower primary structures with a corresponding reduction in framing and sheathing materials.  Display of roof pitches 1/12 through 3/2. This graphic uses run/rise, the inverse of the convention described in the article.  Thatch is one of the oldest roofing materials and needs a steep pitch to drain properly  Some types of stone roofs have a very restrictive roof pitch, too low a pitch the roof will leak, too much pitch the loose stones will slide off.  Shingled roofs with pitches too steep to walk on require a staging of planks on roof brackets. Slater at work, Rothesay, Isle of Bute In building construction, roof pitch is a numerical measure of the steepness of a roof. Roofs may be functionally flat or “pitched”. A roof may also provide additional living space, for example a outdoor roof patio garden The elements in the design of a roof are: * the material * the construction * the durability Support Main article: Domestic roof construction  The roof of a library in Sweden The supporting structure of a roof usually comprises beams that are long and of strong, fairly rigid material such as timber, and since the mid-19th century, cast iron or steel. In countries that use bamboo extensively, the flexibility of the material causes a distinctive curving line to the roof, characteristic of Oriental architecture. Timber lends itself to a great variety of roof shapes. The timber structure can fulfil an aesthetic as well as practical function, when left exposed to view. Stone lintels have been used to support roofs since prehistoric times, but cannot bridge large distances. The stone arch came into extensive use in the ancient Roman period and in variant forms could be used to span spaces up to 140 feet (43 m) across. The stone arch or vault, with or without ribs, dominated the roof structures of major architectural works for about 2,000 years, only giving way to iron beams with the Industrial Revolution and the designing of such buildings as Paxton’s Crystal Palace, completed 1851. With continual improvements in steel girders, these became the major structural support for large roofs, and eventually for ordinary houses as well. Another form of girder is the reinforced concrete beam, in which metal rods are encased in concrete, giving it greater strength under tension. Slate is an ideal, and durable material, while in the Swiss Alps roofs are made from huge slabs of stone, several inches thick. The slate roof is often considered the best type of roofing. A slate roof may last 75 to 150 years, and even longer. However, slate roofs are often expensive to install – in the USA, for example, a slate roof may have the same cost as the rest of the house. Often, the first part of a slate roof to fail is the fixing nails; they corrode, allowing the slates to slip. In the UK, this condition is known as “nail sickness”. Because of this problem, fixing nails made of stainless steel or copper are recommended, and even these must be protected from the weather. Asbestos, usually in bonded corrugated panels, has been used widely in the 20th century as an inexpensive, non-flammable roofing material with excellent insulating properties. Health and legal issues involved in the mining and handling of asbestos products means that it is no longer used as a new roofing material. However, many asbestos roofs continue to exist, particularly in South America and Asia. Roofs made of cut turf (modern ones known as green roofs, traditional ones as sod roofs) have good insulating properties and are increasingly encouraged as a way of “greening” the Earth. Adobe roofs are roofs of clay, mixed with binding material such as straw or animal hair, and plastered on lathes to form a flat or gently sloped roof, usually in areas of low rainfall. In areas where clay is plentiful, roofs of baked tiles have been the major form of roofing. The casting and firing of roof tiles is an industry that is often associated with brickworks. While the shape and colour of tiles was once regionally distinctive, now tiles of many shapes and colours are produced commercially, to suit the taste and pocketbook of the purchaser. Sheet metal in the form of copper and lead has also been used for many hundreds of years. Both are expensive but durable, the vast copper roof of Chartres Cathedral, oxidised to a pale green colour, having been in place for hundreds of years. Lead, which is sometimes used for church roofs, was most commonly used as flashing in valleys and around chimneys on domestic roofs, particularly those of slate. Copper was used for the same purpose. Functions Insulation Because the purpose of a roof is to protect people and their possessions from climatic elements, the insulating properties of a roof are a consideration in its structure and the choice of roofing material. Some roofing materials, particularly those of natural fibrous material, such as thatch, have excellent insulating properties. For those that do not, extra insulation is often installed under the outer layer. In developed countries, the majority of dwellings have a ceiling installed under the structural members of the roof. The purpose of a ceiling is to insulate against heat and cold, noise, dirt and often from the droppings and lice of birds who frequently choose roofs as nesting places. Concrete tiles can be used as insulation. When installed leaving a space between the tiles and the roof surface, it can reduce heating caused by the sun. Forms of insulation are felt or plastic sheeting, sometimes with a reflective surface, installed directly below the tiles or other material; synthetic foam batting laid above the ceiling and recycled paper products and other such materials that can be inserted or sprayed into roof cavities. So called Cool roofs are becoming increasingly popular, and in some cases are mandated by local codes. Cool roofs are defined as roofs with both high reflectivity and high thermal emittance. Poorly insulated and ventilated roofing can suffer from problems such as the formation of ice dams around the overhanging eaves in cold weather, causing water from melted snow on upper parts of the roof to penetrate the roofing material. Ice dams occur when heat escapes through the uppermost part of the roof, and the snow at those points melts, refreezing as it drips along the shingles, and collecting in the form of ice at the lower points. This can result in structural damage from stress, including the destruction of gutter and drainage systems. Drainage The primary job of most roofs is to keep out water. The large area of a roof repels a lot of water, which must be directed in some suitable way, so that it does not cause damage or inconvenience. Flat roof of adobe dwellings generally have a very slight slope. In a Middle Eastern country, where the roof may be used for recreation, it is often walled, and drainage holes must be provided to stop water from pooling and seeping through the porous roofing material. Similar problems, although on a very much larger scale, confront the builders of modern commercial properties which often have flat roofs. Because of the very large nature of such roofs, it is essential that the outer skin be of a highly impermeable material. Most industrial and commercial structures have conventional roofs of low pitch. In general, the pitch of the roof is proportional to the amount of precipitation. Houses in areas of low rainfall frequently have roofs of low pitch while those in areas of high rainfall and snow, have steep roofs. The longhouses of Papua New Guinea, for example, being roof-dominated architecture, the high roofs sweeping almost to the ground. The high steeply-pitched roofs of Germany and Holland are typical in regions of snowfall. In parts of North America such as Buffalo, USA or Montreal, Canada, there is a required minimum slope of 6 inches in 12 inches, a pitch of 30 degrees. There are regional building styles which contradict this trend, the stone roofs of the Alpine chalets being usually of gentler incline. These buildings tend to accumulate a large amount of snow on them, which is seen as a factor in their insulation. The pitch of the roof is in part determined by the roofing material available, a pitch of 3/12 or greater slope generally being covered with asphalt shingles, wood shake, corrugated steel, slate or tile. The water repelled by the roof during a rainstorm is potentially damaging to the building that the roof protects. If it runs down the walls, it may seep into the mortar or through panels. If it lies around the foundations it may cause seepage to the interior, rising damp or dry rot. For this reason most buildings have a system in place to protect the walls of a building from most of the roof water. Overhanging eaves are commonly employed for this purpose. Most modern roofs and many old ones have systems of valleys, gutters, waterspouts, waterheads and drainpipes to remove the water from the vicinity of the building. In many parts of the world, roof water is collected and stored for domestic use. Areas prone to heavy snow benefit from a metal roof because their smooth surfaces shed the weight of snow more easily and resist the force of wind better than a wood shingle or a concrete tile roof. Roof Hail Storm Damage [2ndkey]