If draining to a sump with a vertical overflow somewhere along the box gutter use this calculator.
Box gutter overflow requirements.
An upper roof gutter draining onto a lower roof commonly discharges its flow through a downpipe spreader but regulations do not require a downpipe to be fitted close to the area of guttering that receives the most concentrated flow.
The new guidelines will allow designers to design box gutter roof drainage systems to manage flows of up to 100l s.
However any width can be entered.
Hang the gutter lower the top of the bead must be 20mm below the top of the fascia to allow water to overflow safely over the bead.
The width of the rainhead is to be at least equal to the width of the box gutter and the box gutter needs to be sealed to the rainhead.
All domestic box gutters must be a minimum of 200mm wide and 75mm deep.
Deviations from the gradient must be smooth and prevent towards the outlet without a proportional permanent ponding.
Trial box gutter width the minimum width allowed for domestic projects is 200mm.
2015 3 7 4 layout.
The vba has provided several options for plumbers to make an installation compliant.
Box gutters are designed for a 1 100 ari.
This regulatory oversight commonly results in overflows even though the plumbing may be technically compliant.
Current standards specify compliance with a maximum flow rate of 16l s.
The hydraulic capacity of the overflow device must be no less than the design flow for the associated box gutter outlet.
For commercial projects the minimum allowable width is 300mm.
Gradients box gutter gradients shall not be flatter than 1 200 for sole widths equal to or less than 600mm wide.
Experiment with this figure to get the depth of box gutter you require.
Overflow devices need to discharge to the atmosphere in such a way as.
Rainhead overflow or specific box gutter overflow must be at least 30mm below the height of the back of the box gutter.
For commercial projects the minimum allowable width is 300mm.
There will also be an overflow facility on the side or the end.
Use a 10mm spacer this creates a gap behind the gutter so water can overflow freely.
Code box gutter requirements.
Box gutters must be straight no bends.
This is very important so that water will overflow externally to the building rather than flood into the roof cavity.
This effectively states that all box gutters must allow for 30mm of freeboard which is from the overflow point eg.
A good box gutter design will have falls along its length together with sumps to collect water before it is fed into large downpipes.
Support system box gutter support systems must.
