flat metal roofing

Flat Metal Roofs The Pros And Cons

Common problems with flat roofs and the solutions

Flat roofs are not the main roofing profile in Australia, we tend to build houses with pitched roofs, but flat roofs can be found on many homes and commercial buildings across the country.

See the low pitch roof we recently installed at the Norah Heads Sporties Club in the video below.

One point to address is that a flat roof is not actually flat – There needs to be a pitch to the roof so that water runs off. 
A low-pitch roof minimum is typically a 5-degree pitch on a roof line and the Build Code Of Australia is bringing in guidelines.
Flat roofs are often used as add-on roofing areas such as carports, walkway areas and patios and these need to have a pitch to allow for rainfall. You may have heard of the term Skillion roofs – Well these are also a version of a flat roof

Flat roofs do have their advantages but also have their problems.

If your home has a flat roof (or you’re planning to install one), you should consider these common flat roof problems before you start work.

Why install a flat roof?

Most homes in Australia have pitched roofs, so why do we install flat roofs?

They do offer several advantages over traditional pitched roofs:

  •     They are easier and quicker to install
  •     They are more accessible and allow for easier maintenance and cleaning
  •     They are ideal for solar panels.

The number 1 problem with flat roofs is water and water being unable to drain away. 
Water is your roof’s biggest enemy.

When installing a roof on a new building or even an existing building, we must consider the following factors and remember. Each region in Australia will be looked at differently, as rainfall is a key factor.

We look at the following areas before we can start your roofing work :

  • Rainfall and the intensity
  • Roof size
  • Guttering
  • Gutter fall
  • Gutter outlets 
  • Downpipes 
  • Overflow options

Roof Pitches

Pitched roofs are typically installed because water drainage is more straightforward. Any water that falls on the roof after rain immediately drains into the gutters, protecting your roof from the effects of water damage.

Flat roofs are notorious for their drainage problems.

The water has nowhere to go without a slope, so it can collect in the corners of your flat roof. The water sitting in these areas will cause damage.
Over time, water will start to seep into the roof, causing staining and structural damage and encouraging mould growth and mildew growth.

The solution is good roof plumbing

If you’re considering installing a flat roof, talk to your installer about the correct roof plumbing. 
It is not as simple as putting down regular corrugated panels. These often lead to leaks when there is heavy rainfall.
Corrugated profiles are perfect on regular pitched roofs, but if the roof’s pitch is under 5 degrees, all sorts of issues will arise. Roofing manufacturers recommend that a flat roof (or low slope roof) have a 5-degree pitch as the minimum slope, and they may not provide any guarantees of water tightness if under this. The right roofing profile needs to be selected for the degree of the roof pitch, and for areas that are low pitch, there are 2 widely used metal roofing profiles.


Trimdek can be used as a roof or walling product for domestic and commercial applications.
The 28mm rib height and specially designed capillary groove to ensure water tightness down to a two-degree roof pitch.


Kliplok uses clips to hold the sheets together, which negates needing screws. Screws will always be a weakness over time, and when a screw rusts or falls out – it is an area that water can enter through. It is robust, flexible and watertight.
See here for the roofing options that we offer.

The Right Guttering

Effective gutters and drains are essential to any roof and are significantly more important if you have a flat metal roof.
Regular gutters may not be sufficient; guttering that allows for a larger water capacity may need to be installed. Next, we will discuss the drains and overflows options that can be installed on your flat metal roof to drain water off the roof.

Our favourite gutters are self-cleaning, perfect for a flat metal roof, and they look great!

We recommend a half-round gutter as it empties water faster because of its greater water-carrying capacity than other gutters and this also sweeps away build-ups of silt and sludge with the fast-moving water carrying the build-up away each time it rains.. Check out the Guttering page and the colour options for ACE’s Half Round

Downpipes and drains

We may recommend you install downpipes that can handle larger water amounts such as the 100 x 75mm downpipe. With a volume of 1.8m length 13.5 litres and a flow capacity of 4.4 litres per second. Regular inspections and cleaning are always recommended. If leaves are an issue, we can suggest leaf diverters to prevent leaf litter from clogging your downpipes.


When a new roof is installed, there are gaps where different roof sheets meet or where the sheets or the roof meets the wall.
Other areas where flashing maybe installed are around chimneys and skylights

Flashing covers these gaps and prevents water from entering your roof and causing significant water damage. If you look at the corners or joints of your roof, you will see flashing.
On a flat roof flashing can be an area where water can puddle or be trapped and this can lead to mould growth underneath.
We combat this by taking extra time when installing it and using a waterproof sealant to prevent water from pooling in these areas.
The waterproof sealant will prevent water from seeping under the flashings.

Central Coast Metal Roofers

A correctly installed flatroof has many benefits when you use the right flat metal roof installation experts on the Central Coast.
Get in touch with our Central Coast roofing team today and we can get a quote started and installation date locked in.
We are expecting another wet summer, so get the right team in to fix a problem roof now.

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