What causes a leaky roof?

by Mar 1, 2021Preparation

For most of the year everything is fine and then there is a lot of rain you’re sitting in the lounge room when water drips on your head.  The roof is leaking!  What can you do about your leaking roof?  The cause of a leaking roof can have numerous reasons-

  • Roof damage
  • Blocked gutters and downpipes
  • Loose roof screws and roof material
  • Damaged plumbing in roof
  • Roof design
  • Weather conditions

What are the hazards of a leaking roof?

The roof is filling up with water and escaping through any hole it can find.  This can be through light fittings, ceiling joins, or the roof could just collapse under the weight of all that water.


Household wiring was not made to be water proof.  Wires are just screwed into the back of lights.  And if the roof is damaged the wiring could also be damaged making the ceiling cavity and roof live.  Water and electricity make a deadly mix.  Electricity can electrocute you or short out and start a fire in the roof or walls.

If you have a leaking roof, turn the power off at the mains and get it professionally checked as soon as possible.  If the incoming main is damaged contact your electrical provider to disconnect the house from the grid.  In big storms or cyclones getting it checked may take a day or more as the professionals will be busy.  Don’t get impatient, your life can be at risk.

Collapsed ceiling

Roof structures are designed to hold up the battens, insulation and sheeting.  Add water to the of water picture and the ceiling structurally can’t hold the weight.  Especially if it has insulation batts or newspaper pulp, as it absorbs the water.  Every litre of water adds a kilo of weight to the ceiling.  Being under it when it collapses can cause injury.

Toxic mould

If a roof has been leaking for a while or you ignore it because you can’t afford to fix it.  Toxic mould can build up in the ceiling cavity and spread throughout the house.  Toxic mould is linked to numerous health conditions from breathing problems to immune issues. 

How can water get into your roof?

Guttering and down pipes

Blocked guttering, guttering drains the water away from your roof.  If the gutters are full of leaves, sticks, tennis balls and more the water can’t flow away fast enough resulting in water overflowing the sides of the gutter and can flow back into your ceiling space.  Depending on the roof and gutter design the problem can be minor to the whole house being affected.

Blocked downpipes, the gutters have been cleaned but what about the down pipes?  The same leaves, tennis balls etc. can go down the down pipe and block the water flow.  If your downpipes run underground instead of dropping onto the ground you could have problems with tree roots, or damaged pipes underground blocking the water flow.  If your pipes do go underground have an overflow build into the downpipe.  If the underground downpipe outlet runs into the street gutter and it is full of water it will bank back up the downpipe.




d by the cyclone


Emergency Kit

Roof damage

Rusting box gutter, with the modern design of roofs box gutters are more popular.  Roofs with different angles flowing inward to a central gutter can have more problems than a traditional hip or gable roof.  Box gutters can still fill up with leaves and debris and rust like eave gutters but box gutters are usually over the middle of your house.

Old or damage roof sheeting and flashing.  Old roof sheeting can be rusting developing holes.   Roof sheeting can be damaged by falling tree branches, strong wind, or walking in the wrong place and denting it.  The damaged can be a hole, crack or the sheet is bent or distorted allowing water to flow between the sheets into the roof.  Flashing is the strips placed over the gaps at roof ridges, valleys or where different roof angles meet.

One fix for old rusty roof sheeting is to paint it often thickly.  This is just a temporary solution that can create more problems down the road.  The sheeting will still rusty and the paint hides the damage.  So when someone walks on the roof they can fall through it.

Loose screws, roof screws can let in water by a few different means.  The screw may not have been installed correctly.  Roof screws have rubber washers which can perish with age.  Old roofs or roofs that have been leaking for a while can have the timber roof battens rot letting the screws come loose.  One sign your roof may have had a history of leaking is having each roof screw covered in silicone from previous repairs.

Missing roof sheets.  Strong winds can peel back roof sheets or remove the entire roof.  If the roof has structural failure, evacuate your home as it is not structurally safe any more, walls can move or fall over without the roof holding them up.

Roof tiles moved or damaged.  Concrete or terracotta tiles can crack from impact or by walking in the wrong place.  Tiles are not all tied down depending on your wind zone, non cyclonic areas have limited tie down and can move in strong winds.  Tile roofs can have the ridge capping cement get old, crack and the capping tile can move.

Water pipes damaged in the roof.  Some houses have water pipes running through the ceiling and down the walls.  Damage to the roof or tree branches piercing the roof can damage the water pipes and electricity lines

Roof Design

When designing a house, the average rainfall is used to calculate the roof slope, size of guttering, number of down pipes and more.   Depending on budget and overall design these factors may be minimal.  You can call the emergency services after the rain has gone and they won’t find the cause, that’s because there isn’t anything damaged or blocked.  If this happens often get your roof professionally checked by plumber, you may need the guttering redesigned.

Roof and gutters are not designed for they heavy rainfall at the time.   If you get an above average rainfall the gutters can carry the water away fast enough causing flooding of the roof.  The gutters only carry it as far as the downpipes and they have a limited capacity to drain water so there may not be enough downpipes for the heavy rain.

Roof angle not steep enough.  The flatter the roof the slower the water will drain away.  In heavy rain flat roofs or very low roof angle can have water overflow into flashings or ridge.  There isn’t a quick fix for this problem.

Weather conditions, heavy rain and strong winds can blow water sideways into roof cavities through vents, under roof materials or can lift tiles.


The plumbing in a roof can be damaged by falling trees piercing the roof or part of the roof being ripped off in a storm.  If you have this situation turn the water off at the mains and call a plumber.

Hot water storage tank problem.  Hot water systems can be installed in roof cavities as either electric or a hidden solar hot water system.  The roof damaged can damage the system or the tank may be old and leaking with old age, so you may not need a disaster to have a leak in your roof.

 Multi-storey buildings

Leaks in multi-storey buildings, can be harder to find as the leak as it can be in a different area and travelling though the roofs and floors of the building.  In the lower storey’s the leak could come from leaking plumbing in an upstairs floor and the roof could be fine.



Emergency Kit

What can you do with a leaking roof?

Prevention is better than fixing the problem after the fact.  If you are not a handyman don’t attempt to fix the problem or walk around on the roof.

  • Call a professional.
  • Keep gutters and downpipes clean.
  • Have some professionally check your roof before the raining season.
  • Replace old roof sheeting, painting the roof may be a stop gap measure but it may not stop the problem and just hides the problem for the emergency services.  Painted old roofs can be dangerous to walk on.
  • If building a new home discuss roof design with your designer.
  • If you are building an older building get a building inspection before you make an offer.

What if the roof starts to leak.

  • Turn off the power at the mains
  • Ensure you have suitable tools and temporary repair items in your household emergency kit.
  • Stay out of the room affected as much as possible, but be careful as the whole roof could be filling up and it’s just leaking in that particular room.
  • Be careful if you are tempted to pierce a hole in the patch leaking as a lot of mouse poo laden water can gush out.
  • Call emergency services for advice
  • Take photos from a safe distance for the insurance company.
  • Put your family safety before a few possessions get wet.
  • Move items away safely from the drip in case it gets worse.
  • Consider evacuating your home if it is safe to go outside.

If the emergency services carry out temporary repairs such as tarpaulins get the roof professionally repairs as soon as possible.  The longer the roof leaks the more damage is being down to the whole home.  Temporary repairs don’t last forever, tarpaulins break down in the sun.




Roofs can leak for numerous reasons and it may not need a storm.  With preventative measures and knowing what to do when you do see a leak you can minimise the damage to your home.




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