The Top 19 Causes of Roof Leaks

A roof leak is an issue that can quickly cost homeowners plenty of their time and hard-earned cash, so it’s vital to spot the warning signs quickly and understand why roof leaks happen. While the first thing you see might be a minor drip coming from the ceiling, unwanted water ingress may have already caused significant damage to your property, which means you need to act fast to stop any issues from spreading further.

We know that discovering a roof leak can be a nightmare for homeowners, as they can be incredibly tricky to diagnose without consulting a professional. Your roof is your home’s first line of defence against the elements, so it’s vital to keep it in top condition. To help save you time and money, we’ve compiled a list of the 19 most common causes of roof leaks, including how to identify them, why they happen, and how to fix them.

Common Causes of Roof Leaks

Roof leaks can be caused by many things, but these can broadly be categorised into age-related wear-and-tear, acute damage, and poor installation. Any of these three factors can lead to roof leaks occurring, whether they happen immediately, or decades into your roof’s lifetime

1. Age

Often, the primary cause of a leaking roof is simply that the roofing materials have reached the end of their lifespan. While most roof tiles are designed to last for decades, eventually their level of protection will wane and make them more prone to water ingress. You can stave off this risk with proper maintenance such as removing moss from your roof tiles, but nothing lasts forever. Over time, your roof will be worn down by extreme temperatures, adverse weather, impacts, and debris, all of which can make the tiles more brittle and lead to cracks down the road.

2. Damaged or Poorly Installed Flashing

Lead flashing is a vital feature of a well-protected roof. Flashings are installed along the joints of your roof to seal and protect these weak points from water ingress or unwanted pests. However, if your flashing becomes cracked or damaged, this could quickly become the perfect place for a roof leak to start and cause serious issues. Flashing can be damaged by age-related wear-and-tear, exposure to fluctuating temperatures, direct impacts, or even fixings or caulk falling out of place. If you take a close look at your flashing, any cracks or other damage should be immediately obvious.

Due to the critical placement of flashing around areas such as skylights, chimneys, or simply where two sections of roof meet, it is imperative to repair your lead flashing as soon as possible. To repair broken lead flashing, first remove the damaged section by prying out any fixings, and dressing a new run of flashing in its place. This should then be fixed securely using roofing nails, which you can further protect by using roofing sealant on the nail heads. We’d recommend inspecting your roof’s flashings a few times a year, even if you don’t suspect an issue.

3. Broken or Missing Roof Tiles or Slates

Often, the cause of a roof leak could be damaged or slipped roof tiles. As the primary mode of protection across the majority of your roof’s surface, any sources of damage such as falling debris will likely impact your roof tiles. While many roofing materials are designed to be quite sturdy, they can only take so much before they give. Spotting cracked or missing tiles on your roof is quite simple, and you may notice chips or entire tiles strewn about your back garden after heavy winds.

Compromised roof tiles can cause significant issues, particularly during heavy rain. This is as will now be entering your roof space, burdening your underlay, and seeping into structural timbers, where it can lead to issues such as damp, condensation, and rot. Fixing this issue can be as simple as replacing the tiles. This will involve prying the tiles up and sliding new ones into place. You may find however that the undersarking has begun to rot due to moisture and will also need replacing.

4. Damaged Roofing Membranes or Underlay

As stated above, whilst your roof tiles or slates act as the first line of defence, there’s always the chance that them being damaged could expose the membranes underneath. While roofing underlays such as breather membranes are designed to cope with small levels of moisture and ferry it to your guttering, if forced to bear too much pooling water, this can lead to issues such as the underlay rotting away, or tearing and causing a persistent leak whenever it rains.

5. Using the Wrong Roofing Materials for Your Roof’s Pitch

Roofing materials such as tiles, slates, or sheets, are designed to be installed only on roofs in a certain range of pitches. What’s more, the way you install your roofing differs depending on the pitch of your roof. For example, roofs with a shallow pitch often require a double-layer of underlay to provide the same waterproof protection as more standard pitches. If you, or the roofer you’ve hired gets this wrong however, it can quickly lead to expensive issues such as a leaking roof.

A tiled roof with a low pitch is more exposed to the elements, particularly heavy winds and rain. This is why many manufacturers recommend you leave less of a gap between each tile, and use extra fixings for added security. Roof leaks caused by incorrect materials or installation can be prevented by consulting the manufacturer’s guidelines, and ensuring that the roofing materials you choose are appropriate for your roof’s pitch, and they are installed correctly. Find out how to calculate your roof’s pitch.

6. Poorly Placed Fixings

An easily avoided cause of future roof leaks is when roofing nails or fixings are not secured into the rafters. Missing the rafters means you now have a nail protruding into your roof space, offering a direct route for water ingress and leaks. These are particularly troublesome just after a cold snap, as the nail may frost over during cold weather, but as it warms this ice will turn to water and begin dripping down. This issue can be made worse by poorly ventilated or insulated loft spaces, which are a breeding ground for excess moisture, which will only exacerbate the issue. To remedy poorly placed fixings, you’ll simply need to pry the fixing up and seal the hole left behind.

7. Condensation In Your Loft Space

Condensation is a serious issue that can cause a multitude of problems for homeowners, including roof leaks. As the loft space is the highest part of your home, it is especially prone to condensation due to the way air rises, and of course that it is placed directly between indoor and outdoor temperatures. Condensation is caused when warm air meets a cold surface, so you can see this can be a catalyst. If condensation is a serious issue in your home, this moisture can build up, and eventually drip down onto the floor of your loft, causing water damage over time.

You may notice a leak coming from your loft space, or even just a strong, musty odour from the damp timbers and ensuing issues such as rot, mould, and mildew growth. You can combat condensation in your loft space effectively by installing adequate roof ventilation, which will allow warm air and excess moisture to escape. Another way is improving your loft insulation, which will keep the space at a consistent temperature, and draw excess moisture from the air.

It’s vital to nip condensation in the bud, as it can pose a serious risk to the structural integrity of your roof, particularly if the timbers have been damaged by water for a long period of time.

8. Poorly Installed Skylights or Roof Windows

On a positive note, a leak coming from one of your roof windows is probably the easiest to spot and diagnose, as it should be rather obvious. Do note however, that if leaks are coming from closer to the top of your roof window or skylight, this may indicate that the flashing around it is damaged, rather than the window itself. Aside from acute damage such as impacts from falling debris, or age-related wear-and-tear, a leaking roof window is generally caused by improper installation.

To repair a leaking roof window, first clear the area of any debris, particularly moss or mud. Then, closely inspect every part of your window, to identify any cracks or other forms of damage. Once you’re satisfied that you’ve found everything you’re going to find, seal these cracks using resin or silicone. Even if you don’t suspect it’s the issue, this is also a good time to take a closer look at your window flashing, as some tell-tale signs may be present that it will cause issues in future.

9. Clogged Gutters

Your gutters are the lifeline of your property. A well-functioning guttering system is vital to maintaining a healthy, happy home. However, if your gutters clog, they will cease to function properly and may begin to leak. This will increase your risk of a roof leak as pooling water enters cracks and weak spots in your roof space. It should be easy to identify clogged guttering, as especially in Autumn you may see leaves, twigs, and other debris sticking out of the top. You may also notice that not much water is flowing through the downspout during heavy rain.

Unfortunately, the only way to clean your gutters is to get yourself up a ladder and physically clear the debris. You should begin with your hands or a plastic scoop to remove the largest pieces of debris, which can be disposed of onto a plastic sheet below. Once you’re satisfied that your gutters are clear, you should test them out by pouring water into the top and seeing if it reaches the bottom. We’d recommend inspecting your gutters at least at the start of spring and winter.

10. Cracked Chimney

Our chimneys take a battering over their lifetime, and after repeated exposure to harsh weather, the mortar which holds it all together can wear away, offering an entrance to water. The most common place where a chimney may be causing a roof leak is in the mud cap, or the mortared portion at the top of the chimney. Aside from that, you should also inspect the mortar and flashings around the base of your chimney, to ensure they haven’t been damaged.

Repairing chimneys is difficult, and depending on the issue you’re facing, may require specialist tools. Therefore, if you’ve got a roof leak coming from your chimney, it’s best to leave repairing it to a qualified professional. Whilst this is more expensive than trying it yourself, you’ll be safe in the knowledge that the job is being done right.

11. Ice Damming

Ice damming occurs when ice lines the edges of your roof, forming a dam which prevents snow or rainwater from escaping. This can cause incredibly serious issues, as the weight of pooling water or trapped snow will put significant strain on your roof’s structure, as well as the damage caused by water leaking into your roof space through any cracks or weak points. An ice dam is caused when snow on your roof melts due to the warmth of the home below, and the water runs towards the colder edge of your property where it refreezes, forming an ice dam.

Dealing with damming ice, or excess snow on your rooftop can be treacherous, and in many cases, it may be safer to wait the snow out before tackling it. If you do choose to try to combat this issue, we’d recommend using a roof rake, which will allow you to safely drag snow off of your roof and prevent ice dams from happening. If ice has already dammed along the edge of your roofline, we’d suggest using ice melt to clear it as quickly as possible.

12. Damaged Roof Vents

Roof vents are a vital part of a healthy roof, as they allow warm air to escape, removing excess moisture from your loft space. Without adequate roof ventilation, you’d quickly run into issues such as damp, condensation, and more. Roof vents can cause leaks in a few ways however, whether due to cracks in the vents themselves, or damage to the flashing used to seal around where they protrude from your roof. You can identify if a roof vent is leaking by looking for dark spots underneath where they sit, which indicates moisture ingress.

If you’ve got a leaking roof vent, the first thing to do is use a tool such as a knife to pry up and remove the rubber boot around the base of the vent. Then, pry up any surrounding tiles. You can now replace whichever element was causing the issue, whether it be the flashing, rubber vent boot, or the vent itself. Now, just place the roof tiles back in their original position and you’re all done.

13. Damaged Soffit or Fascia Boards

Soffit and fascia boards protect your roof space by preventing water or unwanted pests from getting into the underside or front. These can become damaged over time however, particularly if your home features traditional wooden soffit and fascia. In tandem with issues such as leaking gutters which can spill over onto the façade of your home, the timber can soften, eventually leading to holes and rot. These areas then become an enticing home for pests such as rodents or birds, as well as water ingress. We’d recommend replacing the soffit and fascia boards with modern UPVC, as this material is virtually immune to all of the issues which plague traditional timber, and are far less likely to cause roof leaks.

14. Poorly Sealed Roof Valleys

As the point where two sections of roof meet, valleys are a common weak point, more susceptible to roof leaks. If the flashing installed along your roof valley has become damaged, or wasn’t installed correctly, it’s only a matter of time before water finds its way in and causes a leak. The easiest way to spot if your roof valley is leaking, is to search for damp spots along the seams of your roof, or alternatively checking that the flashing is still in good condition. To fix a leaking roof valley, it may be necessary to replace the lead flashing, as it’s the most common cause of issues.

15. Working on Your Roof

Many roofing materials are crafted to be exceptionally resistant to whatever the elements throw at them. However, they are not designed to bear the weight of a human being. If you’ve been working on your roof, it’s imperative to tread carefully, only stepping on the apex of tiles, and ideally using boards to guide your way. This is as walking on your roof can easily cause cracks in roof tiles, paving the way for a leak in future.

16. Wildlife

One common cause of roof leaks is when uninvited guests such as rodents or birds make a home in your roof. Animals such as mice or rats seeking shelter will often carve out an area of your roof space to make their den, making any existing holes far larger and more problematic than they should be! The best way to prevent wildlife from calling your roof home is to keep it clean, and clear of any debris, as these pests are often attracted to the presence of fallen branches and leaves. For more information, we’d recommend our guide to stopping birds from nesting under roof tiles.

17. Overhanging Trees

While trees are undoubtedly beautiful and majestic, if the tree in your garden hangs over your roof, you risk damage to your roof tiles from falling branches, debris, bird poo, and more – all of which can lead to roof leaks. Particularly in the Autumn and Winter, if branches and leaves have been falling onto your roof, they may be cracking or chipping away at your roof tiles, and if the leaves find their way into your gutters you’ll soon be dealing with a clog. The best way to deal with overhanging trees to prevent roof leaks is to prune back its branches or even remove the tree altogether.

18. Lean-To Roof

If your home features a garage or extension with a lean-to roof, it’s vital to inspect it regularly. This is especially important if the lean-to is underneath where your main roof often sheds rainwater. The repeated impact of this water, along with increased moisture levels will compromise this roof over time, eventually leading to a leak via the roofing material or its underlay.

19. Punctures or Pooling Water

If you’ve got a flat roof leak, the most common causes are acute damage such as tears or punctures caused by impacts, or pooling water due to improper installation. Both of these can quickly lead to roof leaks, as gaps in the roofing membrane or felt present an easy opportunity for water to get in, and pooling water places increased pressure on the material and structure below.

No Matter What’s Causing Your Roof Leak, Get It Fixed ASAP

We hope this guide has been helpful in teaching you about the most common causes of leaking roofs. Most importantly however, if you are currently dealing with a roof leak, we’d recommend getting to the root of the problem and fixing it as soon as you can. This is because a leaking roof presents many more issues than the immediate annoying drip, and you may find yourself dealing with serious structural problems in the near future.