How To Deal With Flat Roof Leaks [Flat Roof Repair Guide]

How To Deal With Flat Roof Leaks [Flat Roof Repair Guide]

flat roof with water pooling on top of it

Why is my flat roof leaking?

Flat roofs are one of the most common types of roofs in the UK alongside pitched roofs. Most typically used for garage roofs, shed roofs or large commercial and industrial buildings; the flat roof is one of the best types of roofs for your property.

That being said it can be victim to the harsh weather that the UK faces, from cold winters to rainy summers! Therefore, over time, flat roofs can begin to deteriorate and open up to weak areas of the roof, eventually resulting in damages and in particular leaks.

Flat roofs are often victims of roof leaks with some fairly common places that the roof will leak which we see time and time again as a professional roofing contractor working on leaking flat roofs. Furthermore, these typical roofing problems often stem from old age, poor installation and extreme weather conditions all resulting in a leak.

Throughout this article, we will provide you with a breakdown of the reasons why your flat roof is leaking alongside how to deal with a leaking flat roof so that you can choose whether to repair or replace your roof.

5 causes of a leaking flat roof

The five most common causes for a leaking flat roof that we typically see on a day-to-day basis as a local roofing contractor are the following:

  1. Old age
  2. Damaged flashing
  3. Damage to the flat roofs material
  4. Ponding water
  5. Blistering flat roof

1. Old age

The average lifespan of a flat roof is around 15 to 30 years, depending on the type of flat roof. A TPO flat roofing membrane or a PVC flat roofing membrane will last for around 15 – 25 years. Whereas an EPDM roofing membrane can last around 25 – 30 years so it is important to know what type of flat roof you have.

One of the most common causes of a roof leak is simply because of the old age of the leaking roof. No matter the brand or how well the flat roof was installed, there will come to a point in time where your flat roof leaks. This is unavoidable as time goes on, exposure to the UK weather will slowly impact the flat roof so that it begins to deteriorate. Eventually, after years of harsh weather conditions and harsh temperatures, this will result in the roof leaking.

This is one of the most common causes of a leaking flat roof and is one that we typically see on a regular basis when inspecting leaking flat roofs.

2. Damaged flashing

Flashing provides an impervious water membrane to your flat roof that collects any water seeping through and redirects it back out of the roof. Flashing is used as a preventative measure to ensure that your roof does not leak, however, if this becomes damaged or starts to deteriorate, it will begin to lead to the flat roofing leaking and water starting to seep into your home.

Flashing is used to cover any seals and gaps on the flat roof to offer protection against water however when this becomes damaged or gets old and deteriorates water can easily enter from the roof, even through the smallest of damages. Flashing is most at risk of leaking around chimneys, windows, skylights, adjoining walls and roof vents. That being said it is usually due to adverse weather conditions between extreme heat and extreme cold temperatures. Lead flashing will heat up and cool down leading to it to expand and contract. In turn, this reveals the edge it was meant to protect and leads to roof leaks.

3. Damage to the flat roofs material

If the roofing membrane of your flat roof is damaged it can lead to leaks with water being able to seep through the roof. This damage is typically associated with physical and mechanical punctures that result in the flat roof leaking.

This can be caused by anything including people walking carelessly along the flat roof; things such as ladders, scaffolding and tools coming into contact with the flat roof and other sharp options grazing across the flat roof. This all results in the roof taking impact and damage which causes punctures and cracks into the material of the roof.

The flat roof material once damaged can lead to the flat roof leaking and you require a flat roof repair in order to fix the leak.

4. Ponding & pooling water

A flat roof should typically feature a pitch of at least 1:40 so that water and snowfall can exit the roof and nothing pools at the top of the roof. However, this slightly pitched roof may not be enough to completely shed the water and snowfall after a heavy storm resulting in water pooling on top of the flat roof surface.

Most flat roofs and flat roofing materials are built to endure some pooling water on top of the flat roof however if this pooling water is present for more than 48 hours on top of your flat roof there is a much larger risk of water eventually seeping through the surface and into your property below.

If your flat roof is structurally old and at the latter stage of its lifespan, the ponding water on top of the flat roof can result in permanent damage if present for long periods of time. The best way to combat this and avoid your roof leaking is to invest in a flat roof repair and ensure to drain pooling water off of your flat roof if you notice it resting there for long periods of time.

5. Blistering flat roof

One of the most common problems with flat roofs is that they tend to blister resulting in the flat roof leaking. If you identify raised blister-like shapes along the surface of your flat roof it is a common sign that water has got beneath your flat roofing material.

This is due to the fact that water gets in between the gaps in your flat roof and underneath the flat roofing material. In turn, as the water runs down it becomes vapourised by the higher temperatures below leading to the water particles rising whilst being trapped inside the roofing material. As more particles begin to rise this results in pressure building and the roof blistering.

Roofing blisters are usually caused by water ingress where water gets into the weak points of your roof however blisters can also be caused by damp timbers or damp insulation. Blisters are a serious weak point in your roof and went hey give way can cause major roof leakage and thus leading you to have to invest in a flat roof repair.


The potential risks of a leaking roof can be catastrophic for your property for both the structural integrity as well as the belongings inside and the flat roof itself. By ignoring flat roof leaks, your flat roofing alongside your property will continue to endure more damage from the natural elements, therefore, costing you more money in the long run as more major roofing repairs will need to be taken place across the property.

Whereas if you spot these issues quickly and act on them by getting a qualified roofing contractor to inspect your flat roof and work on the repairs quickly, those costs can go from thousands to only hundreds! Thus it is pivotal that you act quickly when your flat roof is leaking to minimise damage, risk and cost for your flat roof.

If you are currently experiencing a flat roof leak and live within the Melksham and surrounding Wiltshire areas, here at A L King Roofing we provide an affordable and fully comprehensive flat roof repair and flat roof installation service that is guaranteed to keep your property protected from the natural elements. With over 40 years of roofing experience in Melksham, you are in safe hands when you chose A L King Roofing.

Speak with a friendly member of the team on 01225 705 918 today and get your flat roofing journey started. 

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