Why the Roof Leaks: 7 Main Causes and What to Do

Main reasons why a building's roof leaks

The primary cause of roof leaks is a breach in the roof's watertight integrity. The most common factors contributing to this issue include:

• **Design flaws**

Incorrectly calculated roof pitch and issues with fasteners are frequent causes of roof leaks.

• **Installation errors**

Leaks often occur due to improper sealing of seams during the installation of flashing or roofing materials, or because of incorrect overlapping of components.

• **Roof wear and tear**

Over time, even the most durable materials can fail, leading to cracks, surface abrasion, membrane damage, metal corrosion, and leaks around the chimney.

• **External factors**

These include clogged gutters, ice dams at roof joints, and mechanical damage caused by strong winds, precipitation, or falling branches.

• **Ventilation system errors**

Poor ventilation in the attic or roof space often leads to leaks around vents and the accumulation of moisture beneath the roof.

• **Condensation issues**

If a waterproofing membrane was not installed during construction, moisture can drip onto the insulation and ceiling.

• **Defects due to improper installation techniques**

This problem most often arises when roofing work is performed by non-professionals or when the wrong type of roof sealant is used.

If the roof of a private house leaks: what to do

Roof repairs must be arranged immediately upon the first signs of damage. This process invariably begins with locating the leak, taking the specific type of roofing into account.

While the shape of a flat roof somewhat simplifies the work, locating leaks on such a structure is often more challenging. This is due to the roof's slope: a leak originating in one section may manifest in a completely different area. Diagnosis involves both visual and tactile inspection. With soft roofing materials (such as roofing felt or bituminous shingles), the surface should be checked for air pockets or water accumulation (often resulting from melting snow). During inspection, look for characteristic salt deposits on the surface.

What should be done if the roof is made of slate, Onduline, metal tiles, or corrugated metal sheeting? A detailed inspection in these cases is often only possible after removing the roofing material. With a pitched roof, locating damage after rain is somewhat easier, as water flows more predictably along the steep slope.

Once the damage caused by snow or rain has been identified, the actual repair process begins, proceeding through the following stages:

• Dismantling the old roofing material. The material is removed from the top down, with simultaneous inspection of the insulation seams. Removal continues until a dry section of the underlying surface is reached. If moisture is present across the entire surface area, the existing material must be removed and the roof re-laid.
• Replacing the roof’s vapor and waterproofing layers. Once the damaged roofing has been removed, the surface is dried—typically using a gas torch. If time and weather conditions permit, natural drying (via sunlight) may be used. Mastics or primers can be used for waterproofing repairs, while the vapor barrier layer is created using a special absorbent film.
• Installing the new roofing material is the final step in resolving the leak. The chosen material is used for the installation, and strict adherence to the manufacturer's installation guidelines is mandatory.