The roof is one of the most important elements of the building, providing protection from precipitation, temperature fluctuations and other external influences. However, even a well-installed roof may lose its tightness over time. Leaks are becoming a serious problem that can lead to damage to the decoration, structure of the building and deterioration of the indoor climate.
Leaks are not only inconvenient, but can also cause serious damage to building structures, finishes, and even human health. In this article, we’ll look at why leaks occur, how to detect and eliminate them in time, and what regulations govern roof protection.
What are roof leaks?
A roof leak is a violation of the tightness of the roofing or underlying layers, as a result of which atmospheric moisture (rain, snow, condensate) penetrates into the structure of a building or room. This may be due to physical damage, material wear, structural defects, or installation errors. Leakage can occur both immediately and after a long time after the problem appears, especially if it is hidden under the trim or insulation.
Types of leaks
Technically, leaks can be classified as follows:
Obvious (open) — water is visible to the naked eye: drips from the ceiling, flows down the walls, spots and streaks appear.
Latent — moisture penetrates into the structural layers of the roofing cake, insulation, beams or floors, accumulates slowly, leading to corrosion, rotting and heat loss before visible signs appear.
Seasonal — they occur under certain climatic conditions, for example, during the off-season, when snow melts or ice forms actively.
Spot and diffuse — spot have a pronounced penetration zone, diffuse are associated with uniform wetting of the entire surface due to condensation or capillary suction.
Even in ancient Rome and Greece, architects and builders paid attention to drainage from roofs. The Parthenon Temple in Athens, built in the 5th century BC, had a pitched roof made of marble slabs with a slope diverting water from the center to the cornices. However, over time, due to earthquakes and partial loss of coating, leaks appeared, which accelerated the destruction of structures in the Middle Ages. This is an early example of how important not only the construction, but also the durability of roofing materials is.
Physics and mechanics of leaks
Leaks occur as a result of the violation of one or more physical barriers of the roofing “pie”, which includes:
Roofing (tiles, metal, PVC membrane, etc.).
Under-roof waterproofing (membranes, films).
Insulation (mineral wool, PIR plates, etc.).
Vapor barrier (prevents the penetration of moist air from inside the building).
Ventilation gap (needed to remove moisture from the under-roof space).
If any of these layers is broken – for example, there is no vapor barrier, the insulation gets wet and loses its properties, condensate accumulates, and moisture, having no way out, penetrates into the structure.
Condensation leaks
Sometimes leaks are not related to damage to the coating. These are the so-called false leaks that occur due to condensation of moisture. In the warmer months, warm and humid air from inside the house rises to the cold surface of the roof, where condensation occurs in the absence of vapor barrier and ventilation — water flows down, simulating a leak. This happens especially often on metal roofs.
During the construction of cathedrals in the 13th-14th centuries in Europe, such as Notre Dame de Paris, architects began using complex roofing structures with beams, copper cladding and gutters. The water was diverted through gargoyles, sculptural drainpipes that divert water from the walls. Despite this, during the absence of regular repairs (for example, in the 19th century), the cathedral suffered from chronic leaks that damaged the interior decoration and frescoes.
Modern realities
Today, even new buildings can run into leaks if installation standards have been violated or substandard materials have been used. Problems also arise during the reconstruction of old facilities: old roofs do not always meet modern requirements for hydro and vapor insulation, and their “restoration” without taking into account the physics of the structure leads to hidden leaks.
Causes of roof leaks
Roof leakage is the result of a number of factors, including design, structural, operational and climatic aspects. The main reasons are discussed in detail below with technical explanations.
Design errors and miscalculations during the design
Designers must take into account both static and dynamic loads (wind, snow, temperature), water flow characteristics, ventilation, type and slope of the roof. Violation of these principles is one of the common causes of leaks.
Examples of errors:
Insufficient slope of a pitched or flat roof: leads to stagnation of water and accelerated destruction of waterproofing.
Absence of vents and ventilation gaps: promotes condensation accumulation.
Incorrectly calculated drainage systems: water flows into places that are not protected by waterproofing.
Since the 2020s, cases of abandonment of mandatory ventilation gaps during the installation of metal roofs have become more frequent in Russia, which has increased the number of condensation leaks.
Physical wear of materials
Over time, any material loses its properties.
Bitumen rolled materials crack over time, lose their elasticity and are destroyed by UV radiation.
Metal tiles can rust in places where the protective layer is damaged.
PVC and TPO membranes lose their flexibility when used improperly.
Insulation materials (especially cheap cotton wool) get wet, crumble and do not hold their shape.
Example: Old Soviet roofs on industrial buildings often had roofing material as the main waterproofing layer. Its service life did not exceed 10-15 years. Today, many of these buildings are leaking, and a complete renovation of the roofing is required.
Mechanical damage to the roof
The roof may be damaged during operation, during maintenance of buildings, due to natural influences.:
Roof damage during snow removal (shovels, crowbars).
Impacts from falling branches, ice, and construction debris.
The impact of hail, especially on soft roofs.
Damage to roofing by birds or rodents (in the case of soft tiles, membrane roofs).
In 1984, a leak of a flat roof in a warehouse was recorded in the United States, caused by a meteorite the size of a tennis ball. This is an isolated but documented case of a "cosmic" leak.
Weather and climatic factors
Harsh winters, sudden temperature changes and strong winds are common culprits of accelerated wear:
The formation of ice and icicles leads to the separation of the gutters and the destruction of the coating.
Thermal expansion causes the seams to crack.
Repeated freezing and thawing of water in microcracks increases their size (the “frost wedge” effect).
Example: Leaks often form on the roofs of buildings in St. Petersburg in the spring, when ice in funnels and drains prevents snow from melting. The water finds its way in through the gaps in the abutments.
Disturbances in the drainage system
Clogging or improper installation of drains and gutters leads to the following consequences:
Flat roof bays.
By pouring water onto the facade of the building.
The formation of water bags that deform the roofing.
The Joint Venture recommends cleaning storm funnels at least 2 times a year — before and after winter.
Hidden causes and operational errors
Lack of regular checkups.
Installation of equipment (antennas, air conditioners, solar panels) without proper sealing of the passages.
Violation of technology in attic insulation: lack of vapor barrier, ventilation.
Conclusion
A leak is not just a hole in the roof. This is a consequence of a violation of the integrity of the building’s engineering system, an error in design, installation or operation. Studying and eliminating the causes of leaks requires a systematic approach and technical literacy.
Regulations and standards for the protection of buildings from leaks
Effective protection of the roof from leaks is regulated by a number of building codes, regulations, technical specifications and GOST standards. They define the requirements for the design, materials, installation, operation and repair of roofing structures. Compliance with these documents is a key element in preventing leaks.
SP 17.13330.2017 - "Roofs"
Regulates structures and materials for all types of roofs (flat, pitched, and operated).
Sets minimum slopes, waterproofing thickness, and requirements for abutments and drains.
Describes the technology of the roofing “pie” device.
Example: According to the Joint Venture, the minimum slope of a roof made of rolled materials is 1.5%, and of metal tiles — 12%. A lower slope leads to stagnation of water and accelerated wear.
SP 131.13330.2020 - "Building climatology"
Sets the calculated climatic parameters (temperature, snow and wind load) for designing a reliable roof.
It is necessary to take into account regional specifics — for example, when designing in Yakutia and Krasnodar, different types of materials and slopes are used.
SP 50.13330.2022 - "Thermal protection of buildings"
Regulates the proper organization of the thermal insulation of the roof and ventilation gaps to prevent condensation, a common cause of hidden leaks.
GOST 32801-2014 - "Bitumen polymer rolled materials for roofs and waterproofing"
Defines the requirements for the physical and mechanical properties of materials: water resistance, heat resistance, flexibility, breaking load, etc.
GOST 24045-2016 - "Profiled steel flooring with polymer coating"
Sets standards for metal roofing, including corrosion resistance, coating thickness, and leakproofness requirements.
Additional standards:
SP 395.1325800.2018 — installation and repair of soft roofs.
Recommendations of TSNIISK named after Kucherenko on roofing at cultural heritage sites.
The codes of installation instructions of manufacturers of roofing systems (TechnoNICOL, BMI, ICOPAL, RUUKKI, etc.) are mandatory when using branded systems, especially in warranty cases.
Historical context: standards in the USSR
In the USSR, GOST and SNiP standards were strictly observed, and roofs often suffered from typical disadvantages.:
flat roofs with poor drainage,
single-layer roofing material without ventilation,
lack of vapor barrier,
unavailability of high-quality materials (for example, membranes or polymer waterproofing).
Flat roofs in houses of series I-515 and II-49 (1950s-1970s) leaked massively after 10-15 years due to inefficient drainage scheme and low slope. This has generated huge budgets for annual "dimpled" roof repairs, often without eliminating the cause.
Modern standards in Europe and the USA
In the EU countries, roofing standards are regulated:
EN 1991 (structural loads),
DIN 18338 (roofing technology),
ETAG 006 (European Technical Approval Directive for waterproofing).
In the USA, the NRC Roofing Manual, IBC (International Building Code) and ASTM D1970 (Bitumen Roll Coating Standards) standards play a similar role.
In Europe, the roof testing system for resistance to water penetration under pressure (Water Tightness Class) is actively used, which is still poorly distributed in the Russian Federation.
Why it is important to comply with regulations
Leaks are often the result of:
failure to comply with the requirements of the joint Venture on slopes and abutments;
the use of non-standardized materials;
violations of the temperature regime during the deposition of rolled materials;
ignoring the requirements for ventilation and vapor barrier.
In the event of an accident, damage or loss of warranty, if deviations from the standards are detected, the owner is fully responsible.
Example: In 2019, a HOA in the Moscow region filed a lawsuit against a contractor after the roof on a new building leaked in 18 apartments. The examination showed that the materials used were not marked with GOST, and the slope of the roof was 0.7% below the norm. The court ordered the contractor to pay damages in the amount of more than 7 million rubles.
Conclusion
Regulations and standards are not a bureaucratic formality, but a systematic protection of an object from design errors, climate risks and economic losses. Compliance with the joint venture and GOST standards is the basis of a durable, airtight roof that can withstand dozens of seasons of operation.
Consequences of roof leaks
A roof leak is not just an unpleasant stain on the ceiling. This is a marker of a serious structural failure that can damage not only the decoration, but also the building’s supporting elements, engineering systems, and residents’ health. The main types of consequences are discussed below, with technical explanations, examples, and facts.
Damage to building structures
Load-bearing elements:
Moisture destroys wooden structures (rafter system, crate, mauerlat), causing rotting, biocorrosion, loss of bearing capacity.
When flowing into reinforced concrete elements, water accelerates the corrosion of reinforcement, especially in the presence of cracks. This is critical for coating slabs, crossbars, and monolithic lintels.
In stone and brick walls, the seams are weathered, the cladding is peeling off and the adhesion of the masonry is destroyed.
Chemical processes:
Increased humidity activates the carbonation processes of concrete, reducing its strength.
In an acidic environment (due to smog and acid rain), metal structures rust especially quickly in constant dampness.
Example: in 2005, in Kazan, as a result of a long-term leak of a flat roof, part of the roof collapsed at a school. The reason is the rotting of the wooden floor beams, hidden behind the drywall.
Damage to interior decoration and engineering systems
Peeling of wallpaper, swelling of paint, shedding of plaster.
The appearance of mold and mildew, especially in bathrooms, attics, and corners of apartments.
Damage to raised ceilings, fixtures and electrical wiring (risk of short circuit and fire).
In buildings with modern utilities, water can disable ventilation systems, fire alarms, and cable channels.
In houses with plasterboard ceilings, even a small leak can bring down an entire fragment of the suspended structure — the moisture-saturated GCL loses its strength and presses heavily on the guides.
Impact on residents' health
Constant dampness contributes to the development of allergic reactions, asthma, and mycoses, especially in children and the elderly.
Mycotoxins released by fungal spores (including Aspergillus and Stachybotrys) have been proven to be toxic and carcinogenic.
The constant smell of dampness reduces the quality of life and causes chronic headaches.
In the 1990s, a study on "Sick Building Syndrome" was conducted in Finland. In 68% of cases, the cause of office staff's poor health was leaks in the roof, which caused mold foci in the suspended ceilings.
Economic losses
Cosmetic and major repairs of an apartment or an entire floor.
Damage to furniture, appliances, and textiles.
Loss of operational and market characteristics of real estate.
Reduced energy efficiency of the building — wet insulation loses up to 60% of its thermal insulation properties, heating bills rise.
Wet mineral wool loses thermal conductivity from 0.036 to 0.110 W/m during roof leakage.·K — that is, it actually becomes thermally conductive like a brick.
Legal and warranty risks
If a leak is detected during the warranty period (usually 5 years according to Law No. 384-FZ “Technical Regulations on the Safety of Buildings and Structures”), the owner may request that the defect be repaired at the expense of the developer.
In case of damage to the property of third parties (for example, neighbors from below), the owner is financially responsible.
When selling real estate with signs of leakage, the market value may decrease by 10-30%.
Precedent: In 2022, the Supreme Court of the Russian Federation upheld the apartment owner’s lawsuit against the HOA, obliging them to pay compensation for flooding caused by a roof leak. The HOA foundation did not carry out proper maintenance and cleaning of storm funnels, which led to local stagnation and leakage.
Systemic risk to the building
In houses with a soft roof, even a local leak often indicates general wear of the rolled coating.
If the problem persists, moisture begins to accumulate in the roofing cake, destroying the insulation, deforming the flooring, forming cavities and cavities.
In the old foundation (especially in panel and block buildings), getting the joints wet can disrupt the tightness of the inter-panel seams, cause cold bridges and leaks along the walls.
Example: In St. Petersburg, leaks at the seams of panel houses of the 137th series were detected in 72% of buildings older than 35 years. In most cases, the source is a leaky adjacent roof.
Conclusion
Roof leaks are not just “uncomfortable.” This:
Threat to construction,
Threat to health,
Financial risks,
Legal disputes.
That is why modern building regulations and roof maintenance are aimed at the preventive detection and elimination of even the most minor leaks. Prevention is cheaper and safer than consequences.
Methods for diagnosing and preventing roof leaks
Early detection and prevention of roof leaks is the key to the safety of building structures, comfort and safety of residents. Modern diagnostic methods make it possible to detect defects even before the appearance of visible consequences.
Visual inspection is the first stage of diagnosis
When used: during regular maintenance of buildings, in spring and autumn, as well as after heavy rainfall or hurricanes.
What is being checked:
The condition of the roofing: cracks, bulges, peeling.
Junctions (to parapets, pipes, ventilation shafts).
Violations of the tightness of seams and drainage elements.
Internal signs: stains on the ceiling, wet areas, peeling of the finish.
According to the building regulations (SP 13.13330.2011 "Multi-apartment residential buildings"), management companies are required to conduct a visual inspection of the roof at least 2 times a year.
Thermal imaging diagnostics
Principle: wet areas emit heat differently than dry ones, especially in the evening or morning. The thermal imager allows you to visualize moisture accumulation zones or cold bridges.
Advantages:
Contactless and secure.
Allows you to detect hidden damage to the roofing pie.
It is effective even in the absence of visible traces of leaks.
Limitations: The method requires dry and cool weather. Incorrect interpretation of images is possible without qualification.
Example: In 2014, a thermal imaging audit of 12 schools was conducted in Moscow. In 9 of them, hidden leaks were found in the insulation of the flat roof, which did not appear visually, but led to heat loss.
Hydro-testing and local humidification
Method: Water is supplied to the roof surface (usually through a sprinkler) with a record of the time, volume and places of leakage in the interior.
Applies:
When the source of the leak is pinpointed.
In disputes between the customer and the contractor (including in court).
Disadvantages: risk of aggravation of leakage, not applicable in winter.
Electroimpedance diagnostics (control of humidity in roof layers)
The essence of the method: moisture affects the electrical conductivity of materials. With the help of special equipment (for example, Tramex Roof & Wall Scanner), the resistance of various layers of the roofing cake is measured.
Advantages:
Precise localization of moisture accumulation at depth.
It does not require opening the structure.
Suitable for flat roofs with a soft coating.
Biodiagnostics and laboratory analysis
Methodology: analysis of air samples and building materials for the presence of mold and fungal spores.
Indications for use:
If hidden leaks are suspected due to indirect signs (the smell of dampness, deterioration of residents’ well-being).
In schools, hospitals, and kindergartens.
In St. Petersburg in 2019, there was a case when roof leaks in the archive of the Library of the Russian Academy of Sciences caused the defeat of historical manuscripts by the fungus Stachybotrys chartarum. The elimination of the consequences lasted more than a year.
Roof monitoring systems
Modern technologies:
Leak sensors: placed under the insulation or between the layers of the roofing carpet.
IoT (Internet of Things) systems: transmit information about temperature, humidity, and pressure online.
Intelligent drainage systems: with automatic diagnostics of blockages and water levels.
Advantage: round-the-clock monitoring without human intervention. It reduces the time between the occurrence of a defect and the start of repair.
Example: Since 2021, the new MSU building has been using a roof cake moisture control system with a GSM module. During the 2 years of operation, 3 potential risks of getting wet were identified, prevented before damage.
Leak prevention: preventive measures
Technical measures:
Regular cleaning of storm drains, funnels, and gutters.
Monitoring the condition of sealants and joints.
Treatment of wooden structures with antiseptics and fire protection.
Scheduled revision and local repairs every 3-5 years.
Regulatory framework: SNiP 3.04.01-87 and GOST 23166-99 oblige operating organizations to carry out current and major repairs of the roof in accordance with the technical regulations and the building passport.
Conclusion
Leak diagnostics today is not only an inspection with a flashlight, but also a whole arsenal of technological solutions, including thermal imagers, sensors, humidity analysis and digital monitoring. Regular roof inspection and prevention allow:
extend the service life of the building;
keep residents healthy;
avoid costly repairs;
to prevent legal consequences.
Leak elimination methods
Fixing a roof leak requires a clear understanding of the roof structure, the type of roofing and the nature of the damage. Mistakes during repairs can worsen the situation, lead to repeated leaks and accelerated destruction of load-bearing elements. In this section, we will look at the main methods of eliminating defects for different types of roofs, as well as analyze typical errors and practical examples.
Elimination of soft roof leaks (rolled, membrane)
Soft roofs are most often used on flat buildings (apartment buildings, shopping malls, factories).
Local repair of rolled roofing (bitumen, Technoelast, etc.):
Cleaning of the site from debris and old pavement.
Drying the base with a gas burner.
Applying bitumen mastic or sealing a new piece of rolled material.
Rolling joints with a roller.
Important: observe an overlap of at least 10 cm and warm up the material to 160-180 °C.
Repair of PVC membranes:
Special welding with a temperature-controlled hair dryer is used.
The joints are lap-welded.
For large ruptures, the installation of patches with reinforcing mesh.
Some modern membranes have an "indicator layer" — when damaged, it changes color, indicating the location of the defect.
Elimination of pitched roof leaks (metal, tiles, slate)
Pitched roofs have a more complex design, and they are more likely to suffer in the areas of joints, fasteners, and ends.
Metal tiles, corrugated board:
Checking and replacing self-tapping screws with worn washers.
Installation of rubber seals and roofing sealant.
Replacement of deformed sheets.
Inspection and sealing of ends and passageways (ventilation, antennas).
Soft tiles (bitumen):
Heating of the defective area with a construction hair dryer.
Removal of damaged shingles.
Laying of a new shingle with bitumen mastic.
Slate:
Replacing cracked sheets.
Sealing cracks and joints with cement-adhesive compounds.
Treatment with anti-moss impregnations (moisture is trapped under the moss).
The standard life of bitumen shingles is 20-25 years. However, if the roof is tilted incorrectly (less than 15°), the service life is reduced by 2 times due to the increased likelihood of water stagnation.
Repair of junctions and drainage systems
Problem areas:
Roof abutments to chimneys, parapets, skylights.
Funnels and gutters of the drainage system.
Skates and ventilation exits.
Technical measures:
Using butyl rubber tape or foil tape.
Installation of metal aprons with sealant.
Replacement of heated funnels (in the northern regions).
Flushing of gutters and drains — especially in spring and autumn.
Error example: In 2018, a leak occurred on the hospital building in Novosibirsk due to the lack of a compensation gap at the end. Water accumulated and penetrated under the tiles. After installing an additional drainage system, the problem disappeared.
Elimination of leaks caused by condensation
The reason: poor ventilation of the under-roof space or lack of vapor barrier. This is especially true in winter, when warm air from the room condenses on the cold inner surface of the roof.
Decisions:
Installation of a counter-grid and aeration fans.
Replacement of insulation damaged by moisture.
Installation of a vapor barrier (for example, a membrane with Sd > 50 m).
Installation of under-roof drippers and condensate collectors.
In Moscow, in 2017, the roof of the shopping center on Kashirskoye Highway was repaired with the replacement of a PVC membrane with a TPO using thermal welding - leaks did not resume after a repeat cyclone, despite previous complaints from residents of a nearby house.
Major roof repairs
Indications:
Coating wear > 60%.
Damage ≥ 25% of the area.
Refusal of local repairs (economically impractical).
Stages:
Dismantling of the old coating and insulation.
Repair of the rafter system (if necessary).
Installation of a new roof pie (waterproofing, insulation, vapor barrier).
Laying of a new coating with reinforcement of the ends and abutments.
Installation of gutters, weather vanes, snow holders, etc.
Example: In 2020, the roof of an apartment building was completely renovated in Perm, replacing slate with metal tiles. The result: a reduction in heat loss by 18% and the complete elimination of previous leaks in the entrance.
Modern materials for eliminating roof leaks
Polyurethane and MS polymer sealants: durable, elastic, resistant to UV and moisture.
Liquid rubber (bitumen polymer mastics): applied by spraying or brushing, forms a seamless membrane.
Waterproofing tapes (Sika, Nicoband): for urgent repairs in any weather.
Repair kits with reinforcing mesh and mastic: for emergency patches.
In the USA, since 2008, the “cool roof” technology has been practiced — repairs using white sealants with high reflectivity (albedo). This reduces not only the risk of overheating and deformation of the roof, but also the cost of air conditioning.
Conclusion
The methods of eliminating roof leaks directly depend on the type of coating, the extent of damage and the technical condition of the structures. The most important principles:
Not to mask the defect, but to eliminate the cause.
Use material-compatible sealants and patches.
Check the condition of the insulation and rafters during each repair.
Record repair work in the inspection log.
Properly executed repairs are not a temporary measure, but an extension of the roof’s service life by 5-15 years.
Results
Roof leaks are not just a local defect, but a potentially systemic problem affecting the safety, energy efficiency, and durability of the entire building. It is important to understand that timely detection and elimination of even a small defect can prevent multimillion-dollar capital repair costs.
Key findings
A leak is always a signal for a technical inspection, since damage can affect hidden structures (insulation, rafters, armature).
The causes of leaks are diverse: from material wear and installation errors to lack of ventilation and condensation.
The consequences can be severe: destruction of load-bearing structures, mold growth, property damage, heat loss, lawsuits, and even emergencies.
Modern diagnostics (thermal imagers, electrical impedance, leak sensors) allows you to find the problem at an early stage.
Repairs must be technically sound, taking into account all the features of the roofing pie, and not limited to “cosmetic” measures.
Prevention is cheaper and more reliable than repairs. Proper maintenance and regular monitoring extend the life of the roof by 2-3 times.
Tips for building owners and management organizations
Maintaining a “Roof Passport”: record all repairs, dates of inspections, identified defects and materials used.
Photo documentation of problem areas: helps to track the dynamics and make claims to the contractor or insurance company.
Conclusion of roof maintenance contracts with professional organizations (especially relevant for HOAs and management companies).
The use of new technologies: IR diagnostics, drones, remote monitoring systems help reduce labor costs and the risk of errors.
The roof is not just a “fifth facade”, but an engineering system that protects the entire building. Taking care of her is not a one—time job, but a process built into a culture of exploitation.
The sooner the problem is discovered, the cheaper and easier it is to fix it. And regular monitoring and prevention is your best ally against disruption, lawsuits, and losses.
EUCLID provides comprehensive solutions for preparing for reconstruction, repair, modernization of existing and implementation of new projects. Our team is ready to take on the tasks within the framework of design and investment activities in construction:
Pre-design study and analysis;
Engineering surveys and design;
Technical and financial support for the implementation of projects;
Inspection of finished objects and completed stages of work;
Construction inspection of buildings, structures and engineering systems;
Technical expertise and audit.
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