Before installing a solar on an older roof, check its condition, the roof structure, tiles or sheeting, and any signs of leaks or damage. Your roof needs to be strong and sound enough to safely support the solar system.

Skipping this step can lead to cracked tiles, leaks, structural problems, or the added cost of removing and reinstalling your panels later.

So, what exactly should you check before solar goes on an older roof, and how do you know whether your roof is ready? Let’s look at the key warning signs and what should be inspected first.

What you'll learn here:

• Why slapping solar on an old roof can be a costly mistake

• The exact checklist every homeowner should run through before signing off

• When to repair, when to replace, and when to just walk away

• How to make sure your solar investment lasts as long as it's supposed to

How old is too old for a roof to go solar?

This is the first question, and it's a big one. Solar panels are built to last 25 years or more. If your roof is already 15 to 20 years old and made of asphalt shingles, it's probably nearing the end of its life.

Think about it, if your roof only has five or ten good years left in it, and you stick panels on top, you're going to have to pay someone to pull those panels off, replace the roof, and then put the panels back on. That's double the labour, double the hassle, and a whole lot of extra cash.

Different roofing materials have different lifespans. Concrete tiles can go 50 years or more. Metal roofing, if it's looked after, can push 40 to 60 years. But if you've got old asphalt shingles that are curling, cracking, or losing their granules, you're on borrowed time.

What's actually holding your roof up and can it take the weight?

This is where things get a bit technical, but stick with me. Solar panels aren't light. A typical 6.6kW system can weigh anywhere from 300 to 500 kilograms once you factor in the panels, the racking, and the mounting hardware. That's a lot of extra weight sitting on your rafters and trusses.

And here's the kicker: one study found that over 80% of existing residential roof structures don't meet current structural loading requirements. That doesn't mean your roof is going to collapse tomorrow, but it does mean you need to get someone who knows what they're doing to check.

You or a roofer need to get up into the ceiling space and look at the rafters. Are they straight? Any signs of sagging? Any timber rot from past leaks? If the rafters are undersized or showing their age, you might need to "sister" them, that means bolting new timber alongside the old stuff to beef it up.

What's hiding under those tiles or shingles?

Even if the surface of your roof looks alright, the real story is often underneath. The underlayment, that's the waterproof layer between your tiles or shingles and the timber deck, can degrade over time.

If that underlayment is brittle, torn, or has holes in it, and then your solar installer starts drilling mounting brackets through it, you're creating a direct path for water to get into your roof cavity.

And once water gets in, timber rots. Rotted rafters can't hold the weight of solar panels. It's a domino effect that can turn a simple solar install into a full-blown roof replacement nightmare.

What about all those flashings and penetrations?

Flashings are those metal bits that seal around your chimneys, vents, and skylights. They stop rainwater from running down the gaps and into your house.

On an older roof, flashings can crack, lift, or just plain rust out. If they're not in good nick, and your solar installer starts working around them or worse, mounting panels over the top of them, you might not even know you've got a leak until water starts dripping through your ceiling.

This is one of those things that's cheap to fix before the solar goes up, and expensive to fix after.

Quick checklist: what to look for before saying yes to solar

Do I need to replace my roof before going solar?

Not always. If your roof is in genuinely good condition; solid rafters, sound underlayment, plenty of life left in the tiles or shingles, you can absolutely go ahead with the install.

But if your roof is showing any of the warning signs I've just talked about, you've got a choice: fix it now, or fix it later at twice the cost.

Most reputable solar installers will do a basic visual inspection before they start work. But honestly, a solar installer is not a roofer. They're looking at your roof from the perspective of "can I mount panels on this?" not "is this roof structurally sound for the next 25 years?"

That's why you should get a licensed roofer or a building inspector to do a proper assessment before you commit to anything. They'll check the things a solar guy might miss; the rafter depth, the decking condition, the structural load capacity.

What happens if I just roll the dice and install anyway?

Look, plenty of people do it and get away with it. But plenty of people don't.

Worst case scenario? Your roof springs a leak around a mounting bracket. Water gets into the timber. The timber rots. The panels shift. The racking pulls loose in a storm. You've got damaged panels, a damaged roof, and a damaged bank balance.

Best case scenario? Nothing happens for a few years, and then your roof reaches the end of its natural life and you have to pay someone to uninstall and reinstall your solar system while they replace the roof. That's thousands of dollars you didn't need to spend if you'd just replaced the roof first.

The bottom line from us

Look, we're not trying to talk you out of solar. Far from it. Solar is one of the best investments you can make for your home and your hip pocket. But we've seen too many people rush into it, skip the roof checks, and end up with a mess on their hands a few years down the track.

At Rural Solar, we've been doing this long enough to know that a good solar install starts with a good roof. That's why we always recommend a proper roof assessment before we even start talking about panels and inverters. We want your system to last 25 years and that means making sure the thing it's sitting on is going to last just as long.

Thinking about solar but not sure about your roof? Give our team a call. We'll talk you through what to look for, and if we spot any red flags, we'll tell you straight-no sugar-coating, no upselling, just honest advice.

Frequently asked questions

Can I install solar on a tin or metal roof that's older?

Absolutely, metal roofs tend to last a long time if they're maintained. But you still need to check for rust, loose screws, and deteriorating seals around the penetrations. The mounting system for metal roofs is different (usually using clamps rather than penetrations), but the structural checks are just as important.

How much does a roof inspection cost before solar?

Typically a few hundred dollars, depending on who you use and the size of your roof. It's a small price to pay compared to the cost of fixing a leak or replacing a roof after the solar is already up.

What if my roof needs repairs but not a full replacement?

That's perfectly fine. If a roofer finds a few cracked tiles, some dodgy flashings, or a small section of worn underlayment, you can get those fixed before the solar goes on. Just factor those repair costs into your solar budget.

Do solar installers check my roof as part of their quote?

Most will do a basic visual check from a ladder or with a drone. But that's not the same as a proper structural inspection. Don't assume they've given your roof a clean bill of health, ask them specifically what they checked and whether they recommend a separate roof inspection.