Overview
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Replacing a roof that already carries solar means the panels come off before the roof and go back on afterwards, which is a separate licensed trade from roofing. The practical risk is not technical, it is coordination: a roof cannot be laid around panels, and a solar installer booked late leaves the system off for longer than necessary. If a roof is within a few years of replacement, doing the roof first and then installing solar avoids paying for removal and reinstallation entirely. On a metal roof, panels mount to the ribs with compatible fasteners rather than penetrating the pan.
Key points
- Panels off first, roof second, panels back last
- Solar removal and reinstallation is a separate licensed trade
- Book the solar installer before the roof, not after
- If a roof is near end of life, do the roof before installing solar
- On metal, panels mount to the ribs, never through the pan
- Expect the system to be off for the duration, and plan around it
Why the panels cannot stay
A roof is replaced sheet by sheet across its whole area. There is no version of that which works around an array bolted to the middle of it.
The panels, their rails and their roof penetrations all have to come off before the old roof does. They then go back onto the new roof, on new mounting, once it is finished.
That is not a roofing job. Disconnecting and reconnecting a solar system is electrical work under its own licensing, which is why it is a separate trade and a separate cost.
The order that works
Most of the trouble on these jobs is scheduling rather than technique, and it comes from booking the trades in the wrong order.
- 1. Book the solar installer first
- Their availability is usually the constraint. A roof booked for a date the installer cannot make means either a delay or a roof sitting open.
- 2. Panels and rails removed
- Done before the roofer starts, ideally the day before rather than the same morning.
- 3. Roof replaced
- Normal sequence, stripped and laid in sections.
- 4. Panels reinstalled on new mounting
- New brackets suited to the new profile. Old rails do not necessarily transfer.
- 5. System tested and recommissioned
- By the installer, not the roofer. Confirm who is signing that off before anybody starts.
If your roof is close to due, do it before the solar
This is the single most useful thing in this article and it applies to anybody currently considering panels.
If the roof underneath is within a few years of replacement, installing solar on it means paying for removal and reinstallation later on top of the roof. That cost is entirely avoidable by doing the roof first.
It is worth having someone look at the roof before signing a solar contract, particularly on a tile roof that has been repointed once already. The solar salesperson is not assessing the roof.
Mounting on a metal roof
Panels on sheet steel fix to the ribs, not through the flat pan between them, because the pan is where the water runs.
Fasteners have to be compatible with the sheet. A fastener from a different material range corrodes against the steel and produces a stain that becomes a hole, years after anybody remembers the panels were installed.
On a tile-to-metal conversion this matters more, because the existing mounting was designed for tile and none of it transfers. Budget for new mounting rather than assuming the old hardware comes across.
What to agree in writing beforehand
Three things, and all three are the sort that get assumed rather than stated.
- Who removes and reinstalls
- Named. Whether the roofer is arranging it or you are, so nobody arrives expecting the other to have done it.
- Who is responsible for the system working afterwards
- The installer recommissions it. Confirm they are testing output rather than just reconnecting.
- What happens if the weather stretches the roof
- The system is off while the roof is off. A week of rain means a longer outage, and it is better to expect that than to discover it.
If this sounds like your roof
We will come and measure it.
Ring and describe what it is doing. If it is a repair rather than a replacement, we will say so.
(02) 9072 1993
