Dos and don'ts for box gutters to minimise maintenance and repair

Box gutters are one of our most common items of roof work here in Sydney.
And box gutters are the most mis-understood element on a roof.
We have a design code in Australia for box gutters - but hardly anyone seem to follow the design code. And this makes for a multitude of problems with box gutters.
A combination of bad maintenance and bad design always cause a lot of damage to a property that is stuck with box gutters.
In this video, we explore box gutters that we often find in all suburbs of Sydney and look at the dos and don'ts of box gutters - that can get you out of trouble.
Many homeowners have to live with box gutters.
So, it pays to know as much as you can about them....
More on our website page: theroofingprofessionalswestsi...
Video on simplified box gutter design is : • Box gutter design for ...

[@ChristianWagner888]

How about: "Don't design the house with a box gutter!"? Much less trouble and lower risk.

[@jetnavigator]

Agree. They seem to be beyond the capabilities of many tradesmen.

[@jetnavigator]

Site Inspections!!

[@ChristianWagner888]

Australia seems to be one of only a few countries that require a sump, whereas in most countries they just connect the downspout directly. What exactly is the function and advantage of having a sump? What can happen, if there is no sump?

[@RoofRepairsSydney]

The sump allows maximum flow in the downpipe by the 'head ' of water that the sump generates. Much like pulling the plug in your kitchen sink that is full of water..

[@ChristianWagner888]

@@RoofRepairsSydney thanks, that makes sense. I guess in the Philippines we make up for the somewhat decreased flow by using multiple 3 to 4 inch downpipes on each really deep (more than 20 cm) gutter. Also, internal box gutters are not as common here, making the whole system less risky.
It's good to know that I might be able to increase overall flow by just adding a sump. I think architects here dislike sumps, because they mess up the clean lines of their design.

[@AggregateUser]

Thanks for the answer mate, as a roofer myself this has helped me understand the function of a sump.
Would you be able to explain the design of a downward overflow device in a sump? It sits higher than the sole of the box gutter - doesn’t make sense to me. Thanks

[@ChristianWagner888]

@AggregateUser one of the main risks of an inside box gutter is that if the main downspout gets clogged, the gutter could overflow into the house or into the structure. I have seen this happen many times during tropical downpours.
One way to solve this is to have an unobstructed overflow that will safely discharge the water to an area outside the building. This overflow is usually not connected to a down pipe.
Australian building codes go into quite a lot of detail regarding these solutions, more than I have seen from other countries.

[@AggregateUser]

@@ChristianWagner888 I own hard copies of these standards. They do go into great detail and are fairly good solutions to heavy rain. All box gutters here need to be designed to tolerate a 1 in 100 years rainfall intensity for 5 minutes, for that particular area.
I just never understood the purpose of the sump, but knowing that it creates hydraulic pressure on the downpipe makes sense. Thanks for your reply.

[@TadiwaMatemera]

Hallow

[@jsmith1899]

Typical Australian building and construction. Some of the worst on earth.