Roof repairs: Detect and fix roof damage at an early stage
Protect roofs. They keep wind, rain, snow, and ice away from us. However, they can only do this as long as they do not affect any major damage to the roof. As a homeowner, you should therefore take preventive measures to ensure that the risk of roof damage is as low as possible. Of course, despite all preventive measures, it may be necessary to have the roof repaired. Then a damage analysis is important and quick action is required.
Each roof consists of many layers with different functions. Roof damage can occur in anyone or in several at the same time. The structure of a pitched roof can look like this, for example:
The outermost roof layer is the roof covering. It usually consists of roof tiles or slate and lies on the roof battens made of vertical counter and horizontal roof battens.
Under the covering, a diffusion-open front covering protects the lower roof layers from rain and dust. It consists of bitumen or plastic.
This is followed, for example, by over-rafter insulation and a vapor barrier. The vapor barrier prevents moisture from inside leading to mold growth in the roof insulation.
Under these layers are the rafters and purlins as a load-bearing part of the roof.
A layer of snow and/or ice lying on the roof surface exerts pressure on the roof structure. It is also called the snow load and must not exceed the values for which the roof is designed. Otherwise, there is a risk of collapse. In addition to roof damage, there is a risk of personal injury. The collapse of the roof on the former ice skating and swimming pool in Bad Reichenhall in January 2006, in which 15 people died, became known. The snow load played a major role in this accident.
The snow load acting on a roof depends on the one hand on the thickness of the snow and/or ice layer. The type of snow or ice also plays a role. The snow load on one square meter of roof area is calculated using the formula “ mean density x thickness of the snow layer ”. According to the avalanche control center in the Bavarian State Office for the Environment, the following values in the unit kg / m³ apply to the mean density of snow types:
For example, if you take a layer thickness of five centimeters (0.05 meters), fresh snow has a load of (0.05 × 100) 5 kilograms per square meter (kg / m²). In contrast, the weight of water-ice is 45 kg / m².
The load can be much larger. Depending on the snow conditions, well over 100 kg / m² act on one square meter of roof area. The incline of the roof surface also plays a role here. Flat roofs are more at risk than pitched roofs. The snow load is often not given in kilograms / square meter, but in the unit kilonewtons / m² (kN / m²). One kilogram / m² corresponds to 0.098 kilonewtons / m².
Roof damage can occur with any roof layer
Each roof consists of many layers with different functions. Roof damage can occur in anyone or in several at the same time. The structure of a pitched roof can look like this, for example:
The outermost roof layer is the roof covering. It usually consists of roof tiles or slate and lies on the roof battens made of vertical counter and horizontal roof battens.
Under the covering, a diffusion-open front covering protects the lower roof layers from rain and dust. It consists of bitumen or plastic.
This is followed, for example, by over-rafter insulation and a vapor barrier. The vapor barrier prevents moisture from inside leading to mold growth in the roof insulation.
Under these layers are the rafters and purlins as a load-bearing part of the roof.
Roof damage: limited functionality, increased risk!
In addition to protecting the residents, the airtightness and energy efficiency of a house are the tasks of the roof. In addition, it must not endanger passers-by with loose components that could fall on the sidewalk. This not only applies to pitched roofs, but also to flat roofs. If functions are restricted or passers-by are endangered, a roof repair is required.Roof damage: the causes
Often times there is more than one cause of damage to the roof and it is important not to ignore any of them. If parts of the roof tiles flake off in freezing temperatures, frost is probably the cause. But of course, other causes play a role: perhaps fine cracks in the roofing due to tired material. If you only have the broken roof tiles replaced, there is a high risk of further damage in the event of renewed frost. You should therefore replace the roof tiles over a large area. Only when you know all the causes of the damage can you optimally eliminate roof damage and reduce the risk of damage. The most important causes of roof damage are presented in detail below.
1) Roof damage: cause "high snow load"
A layer of snow and/or ice lying on the roof surface exerts pressure on the roof structure. It is also called the snow load and must not exceed the values for which the roof is designed. Otherwise, there is a risk of collapse. In addition to roof damage, there is a risk of personal injury. The collapse of the roof on the former ice skating and swimming pool in Bad Reichenhall in January 2006, in which 15 people died, became known. The snow load played a major role in this accident.
The snow load acting on a roof depends on the one hand on the thickness of the snow and/or ice layer. The type of snow or ice also plays a role. The snow load on one square meter of roof area is calculated using the formula “ mean density x thickness of the snow layer ”. According to the avalanche control center in the Bavarian State Office for the Environment, the following values in the unit kg / m³ apply to the mean density of snow types:
For example, if you take a layer thickness of five centimeters (0.05 meters), fresh snow has a load of (0.05 × 100) 5 kilograms per square meter (kg / m²). In contrast, the weight of water-ice is 45 kg / m².
The load can be much larger. Depending on the snow conditions, well over 100 kg / m² act on one square meter of roof area. The incline of the roof surface also plays a role here. Flat roofs are more at risk than pitched roofs. The snow load is often not given in kilograms / square meter, but in the unit kilonewtons / m² (kN / m²). One kilogram / m² corresponds to 0.098 kilonewtons / m².
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In an old building, renovating the roof to increase the load-bearing capacity of the roof structure is relatively complex. Often cheaper jobs are enough. In regions with a high snow load, snow guards are mandatory to protect passers-by from falling snow. Snow guard hooks can also be useful. They distribute the snow that hits the roof and thus prevent high snow loads at certain points. Roof heating can also prevent excessive snow loads from causing roof damage.
Germany is not only divided into snow load zones but also into four wind zones. Wind zone 1 has the lowest and zone 4 the highest base wind speeds. The wind speed only has an influence on the wind load to which your roof is exposed. Other factors are, for example, the shape and height of the roof. The wind load can create wind pressure or wind suction that makes roof repairs necessary. Therefore, the more likely high the wind speeds are in your region, the sooner you should take preventive measures.
Wind suction can be particularly dangerous when wind flows over the roof surface at high speed. Due to the so-called Bernoulli effect, a negative pressure then arises under the roofing. The wind lifts individual roof elements (e.g. roof tiles) and sweeps them off the roof. Air eddies at the edge of the roof are also harmful. That is why DIN EN 1991-1-4 defines rules for the construction of roofs that can withstand the wind loads that can be expected in the respective region.
For better protection, you can protect a pitched roof covered with roof tiles with storm clips. However, you do not have to secure every roof tile with the clamps. Sometimes it is enough if you put storm clips on every second or third brick.
Hail is also one of the more common causes of damage that requires roof repairs. Clay and slate bricks can break from a hailstone size of three centimeters. With hailstones five centimeters in size, tile and shingle roofs are sometimes even destroyed down to the rafters.
To prevent such roof damage from hail, it is best to use materials that are highly hail-resistant. The hail resistance classes assigned in the hail registers of Switzerland (Hagelregister.ch) and Austria (Hagelregister. at) can be helpful. The bandwidth ranges from “1” (very low) to “5” (very high). A German hail register is still pending.
Robust roofing materials are not the only thing that protects against hail. There are also materials for the roof layers under the roof covering, such as special PU rigid foam thermal insulation panels with special hail protection. If the hail destroys the roof covering, they prevent deeper roof damage in the deeper layers.
Moisture may penetrate from the outside:
due to the defective roofing of a pitched roof,
a puddle of water on the flat roof, and a poor seal.
or an improperly executed seal at the connection point between the chimney and the flat roof.
Moisture can also penetrate the roof structure from inside the house in the form of moist air if the waterproofing does not work properly. Mold may then develop inorganic insulation layers. In the even worse case, rotten parts of the roof structure. That is why the entire roof waterproofing should be put to the test in the event of moisture damage. In addition to regular roof maintenance, preventive measures can include work such as clearing clogged gutters.
Despite all precautions, damage can occur and force you to have your roof repaired. As the exemplary fine cracks in the roof tiles show, the need for repair is not always immediately apparent. Regular roof maintenance is therefore useful in order to detect minor wear damage early on. You usually do not have the problem of recognizing the damage that needs to be repaired in the first place in the case of event-based damage cases (storm, hail). The roof damage is almost always immediately recognizable.
Quick damage analysis is important in the event of damage because some damage quickly leads to an even greater damage if you do not take immediate action. A temporary seal may be important to protect the roof structure from further moisture. You also have to ensure very quickly that damage to the roof does not endanger passers-by. But do not climb onto the roof yourself if you are not a specialist. Leave such work to experts.
If there is a chance of the costs being covered by an insurer, it is also important that you document and/or not remedy any roof damage for the insurance company before experts from the insurer have seen it. Sometimes conflicts arise here between the need for immediate measures and the damage documentation. You should therefore contact the insurer immediately after the occurrence of the damage. Discuss all further steps with him.
In the case of immediate repairs, there is often no time for a comprehensive comparison of different providers of roof repairs. But at the latest with follow-up work you should compare the offers of different companies with each other in order to find the best one. The spectrum of possible roof repairs ranges from small work (e.g. with individual roof tiles that have fallen down) to extensive renovations (e.g. after rapid load damage to the roof structure). The scope of the work naturally also affects the level of costs.
What snow load do you have to expect?
If the snow load exceeds the amount for which your roof is designed, the risk of damage from heavy snowfall increases. Repairing the roof quickly becomes expensive. When building and extending a roof, you must therefore take the expected snow load into account. It is higher in the Alpine region than on the coast. That is why Germany is divided into snow load zones. There are zones 1 (lowest snow load) to 3 (highest snow load) as well as fine gradations 1a and 2a. The "a" means a 25 percent increase in snow load. The snow load zone is included in the calculations for a standard-compliant building in accordance with DIN EN 1991 Eurocode 1-3: "Effects on structures - snow loads". This standard replaces the old DIN 1055-5.
Protection against roof damage due to snow load
In an old building, renovating the roof to increase the load-bearing capacity of the roof structure is relatively complex. Often cheaper jobs are enough. In regions with a high snow load, snow guards are mandatory to protect passers-by from falling snow. Snow guard hooks can also be useful. They distribute the snow that hits the roof and thus prevent high snow loads at certain points. Roof heating can also prevent excessive snow loads from causing roof damage.
2) Roof damage: cause "high wind load"
Germany is not only divided into snow load zones but also into four wind zones. Wind zone 1 has the lowest and zone 4 the highest base wind speeds. The wind speed only has an influence on the wind load to which your roof is exposed. Other factors are, for example, the shape and height of the roof. The wind load can create wind pressure or wind suction that makes roof repairs necessary. Therefore, the more likely high the wind speeds are in your region, the sooner you should take preventive measures.
Wind suction can be particularly dangerous when wind flows over the roof surface at high speed. Due to the so-called Bernoulli effect, a negative pressure then arises under the roofing. The wind lifts individual roof elements (e.g. roof tiles) and sweeps them off the roof. Air eddies at the edge of the roof are also harmful. That is why DIN EN 1991-1-4 defines rules for the construction of roofs that can withstand the wind loads that can be expected in the respective region.
Protection against roof damage due to high wind loads
For better protection, you can protect a pitched roof covered with roof tiles with storm clips. However, you do not have to secure every roof tile with the clamps. Sometimes it is enough if you put storm clips on every second or third brick.
3) Roof damage: cause "hail"
Hail is also one of the more common causes of damage that requires roof repairs. Clay and slate bricks can break from a hailstone size of three centimeters. With hailstones five centimeters in size, tile and shingle roofs are sometimes even destroyed down to the rafters.
Protection against roof damage due to hail
To prevent such roof damage from hail, it is best to use materials that are highly hail-resistant. The hail resistance classes assigned in the hail registers of Switzerland (Hagelregister.ch) and Austria (Hagelregister. at) can be helpful. The bandwidth ranges from “1” (very low) to “5” (very high). A German hail register is still pending.
Robust roofing materials are not the only thing that protects against hail. There are also materials for the roof layers under the roof covering, such as special PU rigid foam thermal insulation panels with special hail protection. If the hail destroys the roof covering, they prevent deeper roof damage in the deeper layers.
4) Roof damage: cause "penetrating moisture"
Moisture may penetrate from the outside:
due to the defective roofing of a pitched roof,
a puddle of water on the flat roof, and a poor seal.
or an improperly executed seal at the connection point between the chimney and the flat roof.
Moisture can also penetrate the roof structure from inside the house in the form of moist air if the waterproofing does not work properly. Mold may then develop inorganic insulation layers. In the even worse case, rotten parts of the roof structure. That is why the entire roof waterproofing should be put to the test in the event of moisture damage. In addition to regular roof maintenance, preventive measures can include work such as clearing clogged gutters.
Roof damage: what now?
Despite all precautions, damage can occur and force you to have your roof repaired. As the exemplary fine cracks in the roof tiles show, the need for repair is not always immediately apparent. Regular roof maintenance is therefore useful in order to detect minor wear damage early on. You usually do not have the problem of recognizing the damage that needs to be repaired in the first place in the case of event-based damage cases (storm, hail). The roof damage is almost always immediately recognizable.
Quick damage analysis is important
Quick damage analysis is important in the event of damage because some damage quickly leads to an even greater damage if you do not take immediate action. A temporary seal may be important to protect the roof structure from further moisture. You also have to ensure very quickly that damage to the roof does not endanger passers-by. But do not climb onto the roof yourself if you are not a specialist. Leave such work to experts.
Also important: document damage
If there is a chance of the costs being covered by an insurer, it is also important that you document and/or not remedy any roof damage for the insurance company before experts from the insurer have seen it. Sometimes conflicts arise here between the need for immediate measures and the damage documentation. You should therefore contact the insurer immediately after the occurrence of the damage. Discuss all further steps with him.
In the case of immediate repairs, there is often no time for a comprehensive comparison of different providers of roof repairs. But at the latest with follow-up work you should compare the offers of different companies with each other in order to find the best one. The spectrum of possible roof repairs ranges from small work (e.g. with individual roof tiles that have fallen down) to extensive renovations (e.g. after rapid load damage to the roof structure). The scope of the work naturally also affects the level of costs.
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