How to Detect Roof Leaks — 4 Tried & Tested Methods (+ Cost)

Have you wondered why detecting a roof leak is so difficult?

Some may even say that tracking down the exact location of the leak can be MORE difficult than fixing the leak.

Here’s the problem: the drip inside your house may not be at the exact location of the crack or hole in the roof. Water tends to seep along the roof frame or sheeting and the actual crack can be some distance from the dripping point.

So, before learning how to fix a leaking roof, you need to know how to detect roof water leaks.

Let’s get busy and learn how you can be successful as a roof leak detective.

4 Methods of Roof Leak Detection

There are many perils of a roof leak going undetected. In fact, aesthetic damages like ugly water stains and peeling paint are the least of your worries.

Firstly, leaks can increase indoor dampness leading to blossoming of mould. The wicked combination of mixture and mould can damage the ceiling, walls, and roof structure. Plus, there are associated health risks like allergies and respiratory issues. 

In any case, detecting a roof leak early will help you to avoid a hefty roof repair bill.

And now for the good news.

You may not need to climb up to the leaking roof with a flashlight and try to check the roof for leaks. Modern solutions for detecting leaks involve using advanced methods like thermal imaging, moisture mapping and in some cases, even drones. These tools take the guesswork out of the leak detection process.

There are many types of roof designs used in modern Australian homes. No matter the type of roof you may have, some standard leak detection methods can be used for all types.

1. Visual Inspection

Giving your roof a thorough visual look-over both from the inside and outside is not only a good idea — it also works. Check around the corners, ridges, chimneys, gutters, and vents, as these areas are more prone to damage. Inspect the exterior surface for cracks, missing shingles, or damaged box gutters. 

For complex roofs with multiple roof planes, look at the joints for damages. If you have an attic, check the underside of the roofing for water damage. Sometimes, you may find a small pool of water in the attic space seeping into the floor below.

We suggest that you let the walls dry a bit before tracing the origin of the leak. This will help you figure out exactly where the culprit is.

2. Water Spray Test

One easy tool to detect a leak is your humble garden hose.

For this, you’ll need an assistant with a flashlight to watch the ceiling from inside. Start slightly above the area where the leak has appeared, and let the hose run for a few minutes.

After soaking one spot, move up gradually and use the hose elsewhere. It’s best to work on one side of the leak area and then move to the other.

Once the first drop of water appears, your assistant’s task is to signal that the leak is close to the soaked spot. Depending on the size of the leak, this process will take some time to work. So, be patient.

If it works, great! If not, you can lift the shingles around the leak area for a closer inspection. Shingles can get cracked or curled from ageing and may need repairing.

For flat roofs with extensive damage, a flood test can be conducted with the water depth limited to 25mm. However, the roof should be able to withstand the extra weight of the water. Also, you need to make sure the water can drain properly.

3. Thermography and Moisture Metre

The downside of this method is that, in all likelihood, you won’t be able to DIY it.

The upside is, there are 99% chances that it will work.

Thermography is an advanced method of locating hard-to-detect roof leaks. The thermal devices can see what human eyes cannot and are sensitive enough to detect small variations in temperature and moisture levels.

The camera uses a sensor to detect infrared energy and convert it into a thermal image. Even though heat differentials caused by excess moisture are not easy to detect, a trained professional with a good infrared camera can easily detect roof leaks.

Professionals also combine thermal imaging to detect roof leaks with a moisture metre to pinpoint the leak. Generally, these devices are of two types: pin-type and pinless. The metres have settings for testing different types of materials and when the reading in one spot is higher than the surrounding area, a leak is suspected.

Many buildings like museums and hospitals cannot afford the slightest leakage from their roofs. So they use a 24/7 moisture monitoring system that can be self-monitored.

4. Electronic Leak Detection

This is another method that’s best left to professionals. The reason? Electricity.

Electronic leak detection (ELD) is a method that works on all roof types – including metal roofs – and is often used to test the integrity of newly built roofs. These devices use electric current to detect leaks, based on the ASTM D-8231-19 standard.

Generally, a low-voltage system is used to transmit electricity through a wet roof surface. The technician can detect the position of the leak by using a detector unit. The process can also be used on a dry roof, however, the voltage required will be higher.

But, wait a minute! What about roofs made of non-conductive materials?

In the case of non-conductive materials like wood, the pros use a conductive glass felt or a carbon black primer that is placed on the roof. The other option is to use a deck scanner that detects wet areas below the surface.

What’s the Cost of Repairing Roof Leaks?

The cost of a roof leak repair or restoration depends on multiple factors. First, there are roof size and type, the extent of damage, the materials to be used, and finally, labour costs.

For example, repairing flat roofs is less expensive due to their simple design. In contrast, repairing steep roofs with ridges will cost you more.

Small leaks requiring shingle replacement and patching can set you back between $400 to $800. Major repair works can cost anywhere between $2,500 to $12,500.

Yes, this is quite a big range. But bear one thing in mind. Whatever you have to pay for repairs, the cost of replacing the entire roof is higher.

For minor leaks, you can try DIY roof repairs – if you have the skills. These can involve repairing cracks and damages around vent pipes or around the chimney. However, for repairing major leaks, it is best to get support from pro roof repairers.

Now, if your roof is leaking, is it covered by your home insurance?

It depends on the nature and cause of the leak. Your home insurance may cover roof leaks resulting from damages from falling trees, severe weather, an earthquake, etc. However, if the leak is due to a lack of roof maintenance, you will not be covered. So, get in touch with your insurance company before filing a claim.

How to Detect Roof Leaks: FAQs

How can you tell where a roof is leaking?

The most obvious sign that a roof is leaking is water dripping from the ceiling. Other signs are stains on the ceiling and walls, mould growth, and missing or damaged shingles on the roof.

How to trace a leak in the ceiling?

To detect roof water leaks you can do a visual inspection and then proceed with a water spray test. Other advanced options are using thermal imaging, moisture mapping, and conducting dry or wet electricity tests.

Which method is best for leak detection?

Roof leak detection with an infrared camera combined with moisture mapping is one of the best methods.