Rain doesn’t care how big your roof is. A warehouse, a row of shops, a school block: they all shed water in one big sheet, and it lands wherever the downpipes and flashing send it. Get that wrong and the water turns up in the car park. Or the tenant’s stock room. Or both.
Commercial downpipes and flashing in Perth are the vertical pipes and sealing metal that carry roof water off a commercial building and keep it out of joins, walls and penetrations. According to Jobs and Skills WA (2026), roof plumbers install gutters, downpipes and flashings on homes and on commercial and industrial buildings across the state.
Managing a building? Then commercial downpipes and flashing in Perth deserve a look before the wet season, not after the first leak.
What downpipes and flashing actually do
Definitions first, because people swap these words all the time. A downpipe is a vertical pipe that takes water from the gutter to a stormwater drain, a tank or the ground. Flashing is shaped metal, usually formed on site, that seals the joins where a roof meets a wall, a vent, a skylight or another roof. A gutter is the channel along the roof edge that collects water and feeds the downpipe.
So: gutters collect, downpipes carry, flashing seals. When one fails, the other two get the blame.
Commercial roofs have more of everything. Longer runs, more joins, more openings for air conditioning units, vents and skylights. Every one of those is a spot where water can get in.
It’s not just a bigger house
Same parts. Different headaches. Access comes first. A roof two storeys up with no safe walkway changes how the job is done, and who’s allowed to do it.
According to Jobs and Skills WA (2026), working in construction in WA requires a Construction Induction Card, the white card, and some high risk work needs a WorkSafe High Risk Work Licence. Subcontractors on construction work valued at more than $20,000 must be accredited, or work under someone who is, as a registered building practitioner.
What usually changes from a house:
- Roof size and water volume, which decides how many downpipes you need.
- Access, with edge protection or scissor lifts.
- Downtime. A shop can’t always shut for a day.
- Insurance and paperwork, including who’s responsible if something goes wrong.
Ask how the crew plans to reach the roof. A vague answer tells you plenty. Ask too whether the quote covers making good any roof sheeting that gets lifted to reach the flashing, because that can happen on older roofs.
Get the metal right
Here’s one that catches people out. Some metals don’t get along with a Colorbond roof. According to BlueScope (2026), copper pipes and lead flashing shouldn’t touch Zincalume or Colorbond steel, because of galvanic corrosion. That’s the faster rusting you get when certain metals sit together.
According to BlueScope (2026), lead is best avoided on new work, and soft zinc or aluminium are the recommended alternatives for flashing formed on site. Stainless steel fixings, and fixings with copper in them, are out too.
| Material | BlueScope’s guidance for Colorbond roofs |
| Lead flashing | Not compatible, best avoided on new work |
| Copper pipes | Keep them off the steel, and don’t drain onto it |
| Soft zinc or aluminium | Recommended instead of lead |
| Colorbond or Zincalume sheet | Can be formed into flashing |
| Stainless steel and copper fixings | Not recommended with Colorbond |
Reusing old lead on a roof renewal? According to BlueScope (2026), put a barrier between the lead and the new sheet. A plastic film like polyethylene damp course is the preferred option.
Ask your contractor which flashing material they plan to use, and why, before you sign anything.
Signs something’s wrong
You can spot trouble from the ground. Look for:
- Water staining on walls below the roof edge.
- Downpipes that overflow, leak at joins or have worked loose.
- Rust streaks or flaking paint on gutters and flashing.
- Pooling water at the base of a downpipe.
- Ceiling stains near vents, skylights or wall joins.
Inside, a stain near a roof opening often means the flashing has failed, not that the sheet has a hole. Sort the flashing and the leak usually stops.
And don’t go up there yourself. Roof falls are serious, and a trained crew has the harness and the practice.
What Gutters Perth lists
Gutters Perth lists gutter installation and replacement, gutter cleaning, ridge capping, roof repair, downpipes and flashing, plus a free professional roof inspection in the Perth metro area. Detail is on the gutters and guttering page, the roof repairs page and the gutter cleaning page.
The business advertises a 20 year Colorbond product warranty and a 5 year workmanship warranty. Get both in writing for your job. Its homepage also says it specialises in residential clients, so check commercial work with the team before you plan around it.
More reading: why regular gutter cleaning matters, and what it costs to fix gutters in Australia if you’re budgeting.
The mistake that costs twice
Replacing the downpipe and leaving the flashing alone. The new pipe looks great, the joins still leak, and you’re paying for a second visit a season later.
My view: book an inspection before you ask for a quote. It shows what’s really failing, and it stops you paying for the wrong fix.
FAQ
What are commercial downpipes and flashing?
Downpipes are vertical pipes that carry roof water from the gutter to the drain or tank. Flashing is shaped metal that seals joins where a roof meets a wall, vent or opening. On commercial buildings there are more of both.
Do I need a licensed contractor for commercial roof drainage in Perth?
Commercial roof work comes with safety and registration rules. According to Jobs and Skills WA (2026), construction work needs a white card, and subcontracted work needs accreditation when it’s valued at more than $20,000. Check your contractor’s credentials before work starts.
Which flashing materials suit a Colorbond roof?
According to BlueScope (2026), soft zinc or aluminium is recommended over lead. Copper and lead shouldn’t touch Colorbond or Zincalume steel, because of galvanic corrosion.
How do I know if flashing has failed?
Look for ceiling stains near vents, skylights or wall joins, rust streaks on metal, and water marks on walls under the roof edge. Failed flashing often leaks well away from the actual gap.
How often should commercial downpipes be checked?
At least before each wet season and after big storms. Check for blockages, loose joins, overflow and pooling at the base. Regular gutter cleaning keeps them clear.
Does Gutters Perth offer a free roof inspection?
The business lists a free professional total roof inspection for the Perth metro area. Ask what it covers when you book.
Want a hand? Contact Gutters Perth, call 0468 476 111 or email sales@guttersperth.com. Customer care runs 8am to 8pm, Monday to Saturday, and the business is based on Alga St, Perth WA 6019.