If you can’t see your roof gutter from ground level, then you probably have a box gutter.
This is a typical box gutter configuration
Most houses don’t have box gutters. They have gutters running around the external perimeter of the roofs and these are called ‘eaves gutters’ (even though some houses now do not have eaves).
A box gutter may look like a box because of its ‘boxy’ shape. But the main reason for its name is because it is ‘boxed in’ on all sides. The picture above shows the layout of a typical box gutter on a metal roof.
Typically, a box gutter is ‘trapped’ between two roofs that feed rainwater into it. The water is drained via downpipe nozzles, or via a sumps & downpipes built into it.
A good box gutter design will have falls along its length, together with sumps to collect water before it is fed into large downpipes. There will also be an overflow facility on the side or the end. This is very important – so that water will overflow externally to the building, rather than flood into the roof cavity.
The best box gutter design has full width discharge ends. These pour water into rainwater heads on a wall outside the building. There are no internal downpipes and sumps to block up and cause overflows.
What is the best material for a box gutter?
I recommend that (as a minimum) colorbond should always be used. Some severe situations may call for colorbond “ULTRA” or even colorbond stainless…. although care against cathodic corrosion is needed with stainless.
Box gutters get a lot of moist leaves and debris and these can shorten its life – so the rule of thumb is to have the box gutter material as good or better (in the corrosion department) than the roofing material.
Sometimes I see architectural specifications nominating a colorbond roof with a zincalume box gutter. This combination can result in much higher maintenance costs for the roof.
…Because, the box gutter will need replacement a lot sooner than the roof. And a box gutter replacement is quite expensive and time consuming – because it usually involves removal of the roof sheeting.
It is easier to replace a box gutter together with the roof . Doing it with the roof in place is much more time consuming and costly.
Can box gutters be eliminated?
Unfortunately, with flat roofs, larger complex roofs, parapet walls and other architectural building features, rainwater does not always drain out directly to the external perimeter of the roof.
In these instances, box gutters are the only viable option. So, if your roof is not ‘straight forward’ – then you probably have a one of these somewhere on it.
There is no need to stress out about box gutters…if they are designed correctly with overflows and you carry out regular maintenance.
It pays to have these gutters maintained and regularly cleaned out – simply because a box gutter leak has much higher consequences. Water will go into the house!
Whilst with eaves gutters along the edge of your roof, the water just pours outside when it overflows or leaks.
Are box gutters expensive?
There is a lot more work involved.
There is more thought needed to get a design right and the roof framing tends to be more complex.
Because they are much bigger than eaves gutters, the material cost is greater.
It will certainly cost you more (for the ceiling and internal repair works) if it leaks.
And it takes longer to replace one….
So, the answer is YES.
…. But you may have no option. And if this is the case, then make sure that it is designed and installed correctly in the first instance. Then be fanatical about keeping them clean!
Do you have a leaking box gutter?
Box gutter repairs are often the first option available for you. There are things to keep in mind if you are looking at box gutter repairs.
So, you should pop over to my box gutter repairs page for the next step…