Flat Roof Leaking? The 3 Top Causes of Leaks In A Flat Roof

Flat roof leaking
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Is your flat roof leaking? Have you noticed a new crack forming on your flat roof? Or drips of water falling inside? What about the beginnings of a stain on the ceiling?

These could be signs of a leak in your flat roof. No matter how small the signs are, it’s important to act fast if you think there could be something wrong with your roof, as leaks can lead to further (more expensive!) problems that can cause serious damage to your home. 

In this blog, we’ll cover the three most likely causes of leaks in a flat roof, but first, let’s run through a list of symptoms to watch out for.

Is My Flat Roof Leaking?

A professionally installed flat roof is designed to endure all weathers and last a long time, but it won’t last forever. 

Here are five red flags that suggest your flat roof may have a leak!

1 – Punctures, Holes And Exposed Timbers

A flat roof that isn’t intact will not be able to protect your home against the weather. Rain getting under your flat roof waterproofing can cause damage to the timber below, leading to costly and invasive repair and replacement works. 

2 – Cracks And Blisters

Any imperfections like these signify weak spots in your flat roof and need to be fixed before they worsen and lead to your flat roof leaking. 

3 – Ponding Water

Do you have puddles of water on your flat roof that never seem to dry? This is a sign that the structure of your roof has been compromised.

4 – You’ve Developed An Ecosystem

Have you got a felt roof? Decaying leaves, dirt and moisture provide the perfect conditions for moss, algae, grass and weeds to grow, holding water and compromising your flat roof.

5 – Inside Signs; Mould, Damp And Water Stains

Flat roof leaking? You might have noticed tell-tale interior damage. Without immediate action, water that has found its way inside could spread and cause significant structural damage. 

So that’s the common symptoms covered! But WHY is your flat roof leaking? 

There are a few reasons it could be happening. First up in the top three causes of your flat roof leaking is…

Cause #1: Ageing Materials

flat roof leaking

Why It Happens

Over time, the materials that make up your flat roof can degrade. The layers designed to reflect UV rays and protect the roof from sun damage may have worn away, and the continuous freeze-thaw cycle seen every winter accelerates general wear and tear. 

What To Look For

Different roofs age in different ways. GRP is a brittle material which has a tendency to crack.  Although this can happen due to age, we’ve actually seen cracking and splitting in GRP roofs as little as 3 months old! As GRP (Glass-Reinforced Polymer/Plastic) gets older and is exposed to the elements, the layers of fibreglass can also start to separate (called delamination). This can allow water to get into your roof structure. 

EPDM, or Ethylene Propylene Diene Monomer, is a synthetic rubber commonly used for flat roofs. Sun exposure and harsh weather over the years can cause EDPM to perish. 

Ageing roofing felt is also subject to becoming brittle and cracking. Felt flat roofs are not known for their longevity, with many lasting only 5-10 years. 

The Fix

Any roof will last longer with timely inspections. Repairing an ageing roof is sometimes possible, but it can be more reliable and cost-effective to replace a roof entirely. And whilst some flat roofs only last around 5-10 years, there are longer-lasting solutions you can opt for. Check out our blog “How Long Does A Flat Roof Last?” to learn more about each type… 

Cause #2: Ponding Water

Why It Happens

Standing water that remains on a roof for longer than a couple of days can mean trouble. Whilst it’s sat there, ponding water will be wearing down the roofing material and is at risk of breaching the seams or flashings.

What To Look For

Not sure if you’ve got ponding water? Keep an eye out for concentric rings of dirt on your roof the day after rain. This happens as the puddle of water slowly evaporates and is a good sign you’ve got a standing water problem. 

The Fix

The best way to prevent water ponding on your flat roof is to get it professionally installed and regularly maintain it. 

A flat roof should be slightly sloped to allow for run-off, and drains and gutters must be kept free of leaves and other debris to let the water flow. 

Cause #3: Damage To The Roof

flat roof leaking

Why It Happens

Heavy storms, building works and even vandalism can cause external damage to a flat roof.

In many instances, hard or sharp objects like toolboxes or ladders being physically moved across a flat roof is enough to tear the surface material and compromise its effectiveness. Any damage like this to the waterproof layer, or the flashing or guttering, can cause water to seep in from the outside.

Internally, even a quick DIY job can cause damage to the VCL, or vapour control layer, from the inside, causing condensation to rise from within a building and enter the roof cavity. 

What To Look For

Whilst a tear or puncture hole should be easy enough to see on some flat roofs, physical damage can be trickier to spot on a built-up roof, so routine checking and proper maintenance are key. 

The Fix

Check your roof for signs of damage regularly, especially after storms. Only hire professionals when it comes to working on your roof and if you spot any signs of potential damage, get them checked sooner rather than later. 

Could It Be Condensation? 

There’s one last thing to consider before you descend into sheer panic at the slightest hint of moisture on your ceiling. Rather than your flat roof leaking, the symptoms you’ve spotted could be due to condensation. 

Condensation happens most often when warm, moisture-laden air comes into contact with a colder surface. And it can happen to a flat roof for several reasons.  Poor ventilation is one example – even more so when the room below the flat roof is a steamy bathroom or kitchen.  

If you’re not sure whether the signs you’re noticing are down to a sneaky leak or condensation, follow this link for our brilliant blog on the topic – ‘3 Warning Signs Of Condensation In A Flat Roof’.

Leaks Require Immediate Action

A leak is the final red flag that your flat roof needs attention, and fast. 

Failing to repair or replace the troublesome roof areas in question could mean more costly and invasive building work later down the line if your timber structures become damaged.

Eliminating opportunities for potential damage and scheduling routine maintenance from a professional roofing company is the best way to look after your flat roof and keep it going strong.

In the market for a new flat roof but not sure how to find a reputable company? Overwhelmed by the flat roof options you’ve come across? Read our blog “5 Questions To Ask A Flat Roofing Company Before You Hire Them” and feel confident in your next steps.

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