How to Fix a Leaking Garage Roof

The Ultimate Guide to Leaking Garage Roofs

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Is your leaking garage roof stopping you from using your garage?

Unfortunately, a garage roof isn’t a house roof. And, when the time comes where it needs repair, there just isn’t much help on what to do and how to fix it.

Thankfully, this guide will give you everything you need to get yourself back into your garage, leak free.

In this guide to leaking garage roofs, we’ll cover:

    • What causes your garage roof to leak
    • How to identify sources of a leak
    • What to do if your garage roof is leaking
    • How to fix a leaking garage roof

What Causes Your Garage Roof to Leak?

In this section we will discuss the 4 main causes of a garage roof leak. For each cause we will provide details on how they originate so you can prevent them in future:

1. Old Roofing Panels

2. Garage Roof Condensation

3. Lack of Maintenance

4. Failing Drainage System

1. Old Roofing Panels

Leaking garage roofs are most often caused by failing roof panels.

Old roof panels will erode, crack and scale after decades of exposure to the elements.

This means that garage roof leaks are usually not a DIY project to fix yourself. If your roof panels are old, water ingress is likely to be the start of persistent leak issues.

fixing a leaking garage roof | Danmarque Garages

Leaking Garage Roof Showing Rust, Cracks & Scaling

Concrete roofs such as cement fibre or an asbestos garage roof are particularly susceptible to leaks.

Over time, as their protective layers breakdown, they become porous and retain a lot of moisture.

Eventually, this excess moisture will create cracks in the roof panels to which water will seep through.

This problem is amplified in the cold winter months where frost gets into the cracks and causes them to swell.

Larger cracks means larger gaps for water to leak through.

2. Condensation

Garage roof leaks may be not a leak at all. Condensation can often cause more water ingress than a roof leak.

Condensation inside the garage can occur for many reasons. For example, not having proper airflow to the garage or running sources of heat.

Be sure to check whether condensation is causing your garage to leak before considering a garage roof repair.

You can find out more about condensation in garage here.

3. Lack of Maintenance

The need for flat roof leak repair can sometimes come down to a lack of maintenance.

A few bi-annual checks can help treat a leaking garage roof before it becomes a serious issue:

  • Check for build-up of leaves, dirt, algae, mould or other debris and remove them from the roof surface
  • Check for any small cracks or blistering that is starting to appear
  • Check for standing water and clear from the roof

Even the most waterproof materials like rubber or uPVC need maintenance. Simple checks can help protect your roof from leaks in the future.

4. Failing Drainage System

Failing drainage systems are another cause of water ingress.

A lack of drainage will cause water to pool on the roof or leak onto the walls or floor.

This will cause leaks in places other than the roof.

Check your guttering around the garage roof as well as any downpipes and bracketing.

Make sure they are doing their job in draining water away from the garage.

Failed Garage Roof Draining System | Danmarque Garages

Is Your Garage Roof in Need of Repair?

Get a quote to remove and replace your old garage roof with a 100% watertight roofing system.

How to Identify the Source of a Garage Roof Leak

So, how do you identify the source of a garage roof leak?

First, identify any cracks or holes that are present on top of or on the underside of the roof panels.

Next, check for any gaps in the brickwork or gaps around the garage door opening. You want to check everywhere around your garage, not just the roof alone.

Here is a checklist of what to inspect:

    • Immediate area around the leak
    • Underside of the roof panels
    • Corners of the garage roof
    • Sides of the garage roof where panels meet the brickwork
    • Your drainage system
    • Brickwork (garage walls)
    • Garage door and garage door opening
What to do if Your Garage Roof is Leaking

When you find the source of the leak, do not wait around for the water to cause rotten wood, mould, and damage.

If there is a clear gap that water is coming through, you can use silicone sealant such as LS-X to plug the hole.

If you have eroded panels you will see cracks, rust, rot or a combination of all three. Trying to perform repairs yourself on an ageing roof will cause more harm than good.

The best thing to do is to take note of what has caused the roof to leak, identify where the leak has come from, and speak to a professional garage roof replacement company.

How to Fix a Leaking Garage Roof

Temporary repairs for a leaking garage roof are possible for confident DIYers.

In the short-term, this can prevent the initial leak from damaging the inside of your garage. Long-term though, if your roofing panels are on their way out, this may only delay the inevitable.

DIY repairs may buy you time, the rot, rust, and cracks are tell-tale signs that this is a larger problem with the roof of your garage.


The first thing to do if you’re garage roof is leaking is to move anything important or electrical out of the garage.

Next, identify the source of the leak using the techniques we discussed above.

Now that you have found the source of the leak, identify whether it is a problem you can remedy yourself. Otherwise, speak with a professional about what you can do in the short-term whilst you work out your options.

For example, a garage roof repair or garage roof replacement.

Gather some quotes and make sure you are getting the best value for money. If you are replacing the roof, be sure to take in all information regarding the material it is being replaced with.

You want to be sure that your new roof is water resistant, durable and long-lasting. You also want to check for anti-condensation options. That will shore up all your worries about water ingress in the future.

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