Why roof plumbing gets tested in Hobart
One hour in May 2018
Of the 128 mm that fell on Hobart in the 24 hours to 9am on 11 May 2018, about a third came between 10pm and 11pm. Gutters and downpipes sized for ordinary rain can't shift that much, so water spills over the front or, worse, backs up over the back edge into eaves and walls.
Water off the mountain
kunanyi/Mount Wellington recorded 236.2 mm over those same 24 hours, and Leslie Vale 226.4 mm. Flash flooding followed through South Hobart, New Town and the CBD. If your house sits below a steep slope, ask where your downpipes discharge and whether that connection copes.
Terraces and joined roofs
Battery Point's multi-storey terraces and the inner suburbs' attached cottages often drain through box gutters, internal valleys or a shared gutter at the party wall. These sit inside the roof line, so when they block or rust through, the water ends up in the ceiling rather than the garden.
Steel near salt water
Flashings, gutters and downpipes are steel too. BlueScope measures from the high water mark, and it classes the Derwent south of the Tasman Bridge as exposed, which gets the same distances as Storm Bay surf. Standard Colorbond and Zincalume are only listed past 200 m from either, so a Bellerive house close to the shore can need the same tougher grade as one near Clifton Beach.
What a roof plumber does on a Hobart house
The usual jobs are re-falling gutters that hold water, adding downpipes or bigger outlets, replacing rusted box gutters and fitting an overflow, reflashing chimneys and walls, and resealing valleys. An overflow is a spitter or rainwater head that dumps excess water outside when the gutter can't keep up.
On older homes, one downpipe is sometimes doing the work of two. The building code now asks for eaves gutters to have overflow measures, downpipes as close as possible to valley gutters, and no more than 12 m of gutter per downpipe. Adding a downpipe is a small job next to a soaked ceiling, and our national page on roof plumbing explains the full scope.
Signs your roof plumbing isn't coping
- Water pouring over the front of the gutter in heavy rain, even when it's clean
- Stains on the eaves lining, or on an inside wall below a box gutter
- A downpipe that overflows at the top or gurgles and backs up
- Drips or rust spots at gutter joints and corners
- Damp patches where a terrace meets its neighbour
Questions for a Hobart roof plumber
- Do I have enough downpipes for this roof area in a real downpour?
- Do my box gutters have an overflow, so a blockage spills outside instead of into the ceiling?
- What steel are you using for the flashings and gutters this close to the water?
- Where do the downpipes discharge, and is that connection clear?
- What's your licence number, and does it cover roof plumbing?
What we'd do
If you have a box gutter, start there. Ask for an overflow if there isn't one, because it's cheap protection against a repeat of that night in 2018. Then get the downpipes counted against the roof area. In Hobart it's the short heavy bursts that cause the damage, so plumbing that copes with the worst hour is worth more than anything shiny.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.