Box Gutter Building Regulations

The building regulations set out requirements for many aspects of guttering.

Box gutter building regulations.

Box gutters are essentially placed between parallel surfaces as in a valley between parallel roofs or at the junction of a roof and a parapet wall. This effectively states that all box gutters must allow for 30mm of freeboard which is from the overflow point eg. Also some timber frame details. 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.

Here are some new building regs drawings including mansard roof edge parapet wall box gutter verge detail pitched roof flat roof abutment threshold welted drip for external gutter pitched roof to wall junction pipe through wall joist hangers window frame window lintel window sill manholes soakaway etc. They also give calculations for working out the flow rate that guttering must meet. Read more about compliant guttering options what does it mean for installers. This will prevent water damage in the event of gutters overflowing either due to high rainfall or a blockage.

Have a minimum depth of 75mm at the high end. The expansion joint connector is recommended every 40 to 50 feet i e. The regulations require that guttering has allowances for water to overflow gutters in a way that does not cause water to flow back into the structure. Sometimes i see architectural specifications nominating a colorbond roof with a zincalume box gutter.

Oversize gutters will look wrong. Rainhead overflow or specific box gutter overflow must be at least 30mm below the height of the back of the box gutter. Have a sole width which is not reduced discharge at the downstream end without. Deepflow can be utilised where fall is an issue.

All domestic box gutters must be a minimum of 200mm wide and 75mm deep. Usual rule of thumb is 25m2 into a 115mm gutter with 1 downpipe of 68mm. Have a minimum width of 300mm for commercial installations 200mm for domestic installations. The assembly is made up of four components consisting of two internal end caps one slip cover plate and one slip joint slice plate.

The regulations make sure that rainwater drains away from buildings. As an alternative the top of the rainhead may be installed so that it is no higher than 50 per cent of the flow depth of the box gutter consistent with saa hb39 installation code for metal roof and wall cladding section 5 clause 5 7 3 and figure 5 7 3to prevent internal flooding or damage to the building or contents see figure 2. This is a fairly standard gutter size.