Why Does My Flat Roof Leak?

Why Does My Flat Roof Leak?

Flat roof waterproofing repair

Flat roofs have a reputation for leaking due to the higher tendency that they have for ponding. Unlike slanted roofs, there is no clear visual path for water to run off naturally. As such, water accumulation on various parts of a flat roof can lead to penetration and leaks over time.

It is true that flat roofs are at greater risk of water seepage as compared to traditional slanted roofs. However, in many cases, water leaks from flat roofs are due to poor workmanship or a lack of regular maintenance. A well-designed flat roof should be able to withstand water penetration.

Before we explain how a flat roof should be waterproofed, we first need to understand what exactly is a flat roof.

What is a Flat Roof?

To be clear, flat roofs are not actually flat. They have a slight slope, up to approximately 10 degrees that allow for rain water to be drained off the roof. Typically, flat roofs are used in dry climates. Since less rainfall is expected, it creates extra space for occupants to use. Common facilities that are built on flat roofs include drying areas, mini gardens and barbeque corners.

Flat roofs are economical to construct as they reduce the volume of your building. Oftentimes, they are made from masonry or concrete as these materials are effective at keeping the heat of the sun out from the house. Additionally, both masonry and concrete are affordable materials that are easy to work with.

For wet environments with expected heavy rainfall, it is advised that flat roofs be avoided. While good workmanship will ensure a strong resistance against water penetration and well-designed water pathways, the tendency for ponding is larger due to slower drainage. Additionally, if the climate also features low temperatures, then water that has penetrated the surface may freeze and expand, causing the construction material to break up.

4 Common Causes For Water Leaks From Flat Roofs

We have identified 4 common causes for leaks from flat roofs. These are ponding, obstructed drainage, damaged membrane and points of vulnerability.

Ponding on Flat Roofs

Ponding is characterized by any body of water that remains on your roof for longer than 48 hours from the period of precipitation. Where poor workmanship is done during the construction phase, water will not travel as intended towards drainage points. Instead, due to either poor angle calculation or incorrect path construction, the water will not be drained off naturally. Subsequently, water will gather at a point of rest on your roof.  

It is critical that you monitor your roof after each rainfall to observe for any signs of standing water. Even where no leak has been observed, you need to be aware of prolonged standing water as the additional weight of the water will increase the chances of penetration down the line.

Choked drain flat roof flooding

Obstruction of Drainage Points

A major contributor to ponding is that of blocked drainage systems. All flat roofs have at least one drainage point that is used to usher water off the roof. However, they are prone to becoming excessively choked with debris. Debris range from fallen leaves to foreign human objects.

Regular checks on the drain must be conducted while any debris should be cleared. It is not unheard of flat roofs whose drainage points have been choked, to end up with a pond that is 10m deep. To help prevent such, you should purchase and install leaf guards.

Areas With Roof Penetrating Structures Are Vulnerable To Water Penetration

Often times on a flat roof, you will find protruding structures such as vents, pipes and gasolines. Unfortunately, flat roofs are particularly vulnerable to water leakage around the areas of these structures. This is because there is an increased likelihood for gaps in the surface to be at the point where such structures meet the roof.

To protect these areas against leaks, different tactics can be used. These include the installation of flashing, field wraps, pipe boots and rain collars. However, it should be noted that these installations only help to limit water penetration and not waterproof them.

Flooding surface water leakage

Flat Roof Leakages Due to Damaged Waterproofing Membranes

All roofs require waterproofing membrane installation in order to truly prevent water seepage. A waterproofing membrane is a thin layer of waterproofing material that is laid on surfaces to stop water ingress. Compared to the layering of multiple construction materials, they offer a more affordable and easier to install alternative.

Unfortunately, waterproofing membranes are subject to wear and tear as time goes on. Symptoms of damage to a membrane include splits, cracks, blisters and punctures. Once a waterproofing membrane is compromised, water is able to access the vulnerable insulation layer that typically lies below the membrane. As more water gets trapped in the insulation, leakages into your interior will slowly develop.

Well-constructed and applied waterproofing membranes last between 20 to 30 years.

Similar to checks on your drainage, regular inspection of your waterproofing membrane needs to be conducted to ensure that they are still operational.

Inspecting Suspected Leaking Flat Roofs

Inspections of your flat roof for water ingress can be a tricky task. Water is highly capable of travelling considerable distance horizontally. As such, their point of entry may be well concealed and far from your weather exposed surfaces. Professional waterproofing companies use a combination of visual inspection and commercial moisture meters.

Careful visual inspection is always first conducted to find the water drainage points and designated pathways for water to flow. Any anomalies are picked out here, including that of debris choked drains or blocked paths. Tests for ponding may also be conducted while signs of cracked roofs are searched for.

Moisture screening equipment such as moisture meters, infrared imaging and thermography are used to scan wet areas below any membranes, thus allowing the professionals to find probable leaking points. One limitation exists with such equipment. If too much time has elapsed since the point of precipitation, then water may have flowed to other parts of your home, far from your roof. In which case, the equipment will be less accurate in picking out the probable leaking points.

Flat roof water leakage maintenance

Choose ProSeal Contracts for Your Flat Roof Waterproofing Needs

ProSeal Contracts is a waterproofing company in Singapore with more than 20 years’ experience. As one of the leading waterproofing contractor companies, we use the highest quality of materials to ensure long lasting results. Trust us to assess, choose and apply the right waterproofing procedures for your building’s needs.

Our waterproofing methodology for a RC Flat roof is a 5 coats that ensures years of protection against water leakages. Addintioanlly, it insulates against deterioration from carbonation, acid or chemical attack

Find out more about ProSeal Contracts’ flat roof leak repair or flat roof maintenance services today.

Experiencing leakages in a different part of your home? Unsure how to find the source of the leak? Read our article: “How to find a water leak in your house?

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