7 most common reasons why roofs leak

7 common reasons why roofs leak

Leaking roofs are as common as the number of rainy days in Sydney.

We have spend many years repairing leaking roofs in Sydney and we have a decent database containing the causes of roof leaks. Most roof leaks fall into the categories below. If your roof is leaking, then you will quite likely be able to find out the causes on this post.

There are always exceptions to the rule and some roof leaks are quite hard to track down and this is where we can be the most use to you. The uncategorised roof leaks will stretch our knowledge base and I come across these from time to time. Sometimes, I feel like throwing up my hands and giving up.

…..But the challenge of finding the cause(s) of a leak and fixing it is always met with dogged determination.

The 7 most common causes of roof leaks are (now there are 8 because the blocked gutter category rears its ugly head so often recently):

This is a typical faulty skylight

This is a typical faulty skylight

1) Skylights:

As soon as holes are cut on a roof to put skylights in, the natural waterproof nature of roofs are violated. Some skylight installations leak the day they are cut into a roof. This is usually the result of a poor selection of skylights or a faulty installation. Then during its life, leaf blockage is the usual reason for skylight leaks. Finally, the life of a skylight is usually less than the roof – so old rusty skylights leak and will need replacement.

I have a FAQ page dedicated to leaking skylights … <so pop over there if you think your skylight is the problem.

There is also a page about choosing skylights …<



2)  Broken roof tiles: cracked-terracotta-roof-tile-thumbRoof tiles do not often break by themselves. If you have overhanging trees, falling branches will break tiles. As soon as you let people walk on your tile roof, there is a danger of broken tiles. Children like throwing things and these things can break fragile roof tiles. The worst I have seen is freshly broken roof tiles caused by another roofer (doing a roof inspection and quote) and just left there. We always carry spare roof tiles around with us and replace any that we break during roof inspections… but it clearly seems that other roofers do not bother.

Broken roof tiles can be repaired (if a replacement is not handy)

A break on a roof tile can be quite difficult to trace if it is on the water (drainage) course. I have a post about these tricky leaks caused by broken water courses.


rusty valley3) Rusty or blocked valleys: While tile roofs do not rust, there are valleys on most roofs and in the old days, they just used galvanised metal valleys. These have a 20 to 30 years life … so rusted valleys are quite common on Sydney roofs.

Leaves and valleys do not go together. If you have leaves crammed into your valley, a sudden downpour will create a dam. A rush of water will spill over the edges of the valley and you will see water gushing out of your ceiling…

I have a page dedicated to roof valleys.. < so pop over there if you have a valley problem.



PageLines-watertrappedbehindcrackedbeddingatridgecapping.jpg4) Faulty tile ridge capping: The bedding and pointing under tile ridge capping crack over time. Water seeps into the cracks and does three things.

…It can pool behind the bedding (if it is sealed to the roof tile) on the roof tile and eventually overflow into the roof cavity (this is why weep holes are essential).

…It can run along the back of the bedding, find a drainage path along the tile and seep out again – with out causing any harm (the usually case).

…Or it can run along the back of the bedding and NOT find a release drainage path, but the edge of the roof tile. The result is a leak. These leaks are hard to spot without removing the ridge capping first.

If you want to find out more about weep holes and ridge capping repair work < go to my dedicated pages on this subject.


chimney fault5) Chimneys: A chimney is another hole on the roof that needs to be waterproofed correctly. The flashings around chimneys deteriorate and often cause leaks. Chimney pots break.

Most tile roofs have lead soaker flashings on the upstream side and the lead will crack after a while. A simple fix is to reseal with silicone sealant. The expensive alternative is to replace the flashing with a new one.

Some chimneys have hidden soaker flashings along the side and these can also rust out.



1 oxford rear gable gap in flashing6) Faulty flashings: The edges of roofs have to be waterproofed by flashings. It takes a lot of roofing experience to be able to detail complicated roof flashings so that they look good and do not leak. If a new roof leaks, then the roofer usually has made a mistake on the roof flashing. We can usually gauge the quality of the roof installation by how the flashings are finished off.



rusty roof7) Rusty roofs: This reason may seem quite obvious. It is easy to see if a roof is rusty. But it takes a while between when a roof begins to rust and when holes form and water starts dripping. Also, often, the rusty areas are very localised and hidden. In these instances, only close inspection will reveal the rust spots at laps and under flashings.



blocked gutters8) Blocked gutters: I am adding this to my original 7.

Blocked box gutters  can cause havoc if there are no overflows to act as a relief valve system. If you experience flooding inside your house and you have a box gutter – then it is quite likely a blocked outlet in your box gutter. The temporary solution is simple – just clear off the blockage. Long term, a system to prevent the blockage and overflow protection is needed.

Normal Eaves gutters are often left full of leaves and  this will start a nice garden in the gutter as well as overflowing gutters. They do not normally cause problems with leaks into the house. The exception is when the eaves extend over windows. Overflowing water will run along the eaves and fall onto the head of the window – causing a cascade of water along the inside of the window.


Beware the Gypsy Roofers in Sydney’s Inner west

The Daily Telegraph published a story on 29th August 2011 about Gypsies doing dodgy roof repairs…

Daily Telegraph warning about Gypsies

A few years ago, I came across a reported case of ‘Gypsy Roofer extortion’ in Sydney’s inner west while investigating a roof leak.

The story goes…

…A couple of roofers knocked on the door of this house in Sydney’s inner west and told the house owner that she had some loose tiles at the front of the house. They said that they could fix it for $200. They were very presentable and dressed had roofers shirts on – so the lady agreed.

After doing some work on the front of the house, they came down with some bad news. The rest of the roof also needed work and they could do it straight away for another $1000. Somehow, they extorted an agreement from the lady and proceeded to start work.

… Meanwhile, the lady has some ill feelings and rung her husband at work. They agreed that since they were there, she may as well let them complete the work to the roof.

Soon, it was time for the roofers to collect their payment, and things started to go wrong. Firstly they demanded a payment of $1700.

Fortunately, the lady managed to contact her husband again and he managed to get home quickly… The gypsy roofers explained that their Irish accent may have confused the lady. She must have confused $1000 with $1700. It was not until the husband demanded a building or contractor licence from the Gypsy roofers that he managed to get the upper hand (since gypsy roofers hold no licences)…

It became quite a tricky situation and rather than not pay the Gypsy roofers anything, the couple finally ended up parting with $1000. The lady was dead scared that the gypsy roofers would return when she was alone and pay retribution because they did not get paid…

It would not have been so bad if the gypsy roofers did do a good job on the roof. The home owners had no idea what sort of work had been done until they called me in to trace a water leak. The roof was in a worst state that before it got ‘fixed’- and because of the work done, it would cost more to undo the work before the proper roof repair job can be carried out…

The video below tells the story better.

The best advice for all homeowners is NEVER to let anyone who door knocks anywhere on your roof to start doing work. Ask for their credentials and a written quote first. Then give yourself some time to check them out before contacting them again if you would like them and want them to work on your roof.

Gypsy roofers

Save yourself from travelling CON men attacks

And if you want more information about these “Travelling Con Men” visit the NSW fair trading website. You may save yourself a lot of heartache… There is a link there to a facebook page about travelling Con men