- By Liam Ridings
- In Blog, Metal Roofing, Renovation
How much overhang on metal roof for gutters?
Gutters on your roof are essential for protecting your building’s structure. If you’ve got a metal roof installed, chances are you’re wondering how far should roof sheets overhang the gutter. Too much over the gutter, and water will miss it altogether and start to erode soil at the base. If you don’t have enough overhang, water will drip down the side of the building.
So how much overhang on a metal roof for gutters is enough? Join Vertec as we answer your gutter placement questions and how to optimise positioning to protect your building.
How far should roof sheets overhang guttering?
In general, the ends of metal roof sheets should overlap into the trough of the gutter by around 50mm. Any more than this, and the increased speed with which water drains down the smooth metal surface will see the water miss the gutter altogether.
Water runs down metal roof sheets much faster than it does roofing made from asphalt, wood, or terracotta shingles. Roofs constructed with clay tiles or asphalt shingles possess enough friction to slow down the flow of water during a storm. As a result, it is possible to have these roofs overhang further above the gutters compared to a metal roof.
The importance of a small amount of overhang, is that it offers some protection from leaves, sticks and larger debris from falling into your gutter and causing blockages. Overhang on a metal roof is often accompanied by a downspout screen that acts as another layer of protection.
Importance of gutters
You might wonder, do I even need to worry about how much overhang on metal roof for gutters? Why don’t I just forget about gutters completely? The reality is every building needs gutters. Gutter systems prevent erosion around the base of your home, protect garden beds and other features below, protect the sides of your building, and most importantly, they help protect your roof.
Exact overhang on a metal roof depends on a few factors:
Gutter size:
According to the National Construction Code (NCC), gutter widths must be between 115mm to 150mm, and be in line with the joint Australian and New Zealand standards. The width you select for your gutter will determine the exact answer to how much overhang on metal roof for gutters in your home.
Climate:
The NCC has climate-based provisions that dictate building standards when it comes to adding a gutter. In areas with pronounced rainfall throughout the year, you will need to install gutters that have adequate catchments to ensure water is diverted from the ground of your building. These standards will then impact the construction of your metal roof, and its minimum overhang.
Drip edges are recommended for metal roofs in high wind areas. Strong gusts of wind in some regions of Australia are very capable of getting under your overhang and ripping your metal roof off. Too much overhang can only increase this risk.
Pitch of the roof:
Got a steeply pitched roof? The size and degree of your metal roof play a part in the water flow running from it during a rainstorm. Large steep metal roofs, at close to 90 degrees, will not demand as much overhang over a gutter in Australia compared to flatter roofs with smaller areas. Water flows up to 40% quicker across a metal roof, so it’s essential to keep that in mind when considering how far should roof sheets overhang gutters in your building.
Other factors affecting roof sheet gutter overhang
A slightly different type of gutter called a ‘valley gutter’ is an exposed open gutter located between where two main sections of a roof meet and change direction. Valley gutters on a pitched roof must be at least 400mm wide, with 150mm of metal roof covering the two sides. This only applies to pitched roofs over 12.5 degrees.
Important note on metal roof overhang
When considering the overhang on your metal roof, your roofer must install gutters that attach to the fascia board of your building, not the roof deck itself. With the increased velocity of water cascading from the metal, the gutters need to be reinforced to manage this extra water.
Wrapping up
You should always fit gutters on your metal roof. Even if you think you can lower your roofing costs by using metal, never skip on the guttering. Gutters on your roof should be reinforced and attached to the fascia to manage the extra water shooting off your roof, and should have enough overhang to catch the water.
When thinking about how much overhang on metal roof for gutters, around 50mm should be enough. However, this is affected by your climate, frequency of precipitation, size of your roof and the size of your gutters.
Like anything to do with home maintenance, a metal roof overhang is best left to the professionals. That’s where Vertec comes in. We’re the leading roofing company across Sydney and Canberra, offering effective gutter installation to your metal roofing that is up to NCC standards. When it comes to how far should roof sheets overhang gutters in your home, let the professionals install them correctly. Get in touch with Vertec Roofing today for a quote.
