Does Your Roof Need Work Before Solar? Age, Condition and the Question Nobody Asks Until It's Expensive

October 9, 2026

Here is a question that almost never appears on a solar quote, and probably should: how much life is left in the roof you are about to cover up?

Solar panels are designed to work for around 25 years. The covering underneath them - the tiles, the slates, the felt - has its own clock running, and the two clocks rarely started at the same time. If the roof gives up in year eight of a 25-year solar system, you do not just pay for a roof. You pay for a roof plus taking the panels off plus putting them back on again.

This is one of the few places in home solar where a bit of thinking upfront saves real money. So let's work through it calmly, without anyone trying to sell you a roof.

The simple version

The rule of thumb used across the industry is straightforward: your roof should have at least 10 to 15 years of life left in it before you put panels on top.^[1]

Translated into practice:

Roof under 10 years old, no known problems. You are almost certainly fine. Go ahead.
Roof 10 to 20 years old. Worth a proper look before you commit. Not a red flag, just a reason to get eyes on it.
Roof over 20 years old, or showing wear. Have the roof assessed first. There is a real chance the sensible order is roof, then panels.

That is the headline. But "roof age" is doing a lot of work in that sentence, and it means very different things depending on what your roof is made of.

Your roof covering matters more than the number of years

A 30-year-old concrete tile roof and a 30-year-old natural slate roof are in completely different situations. Rough life expectancies for the coverings common across Germany, the UK and Italy:

Covering	Typical life	Notes for solar
Natural slate	80-100+ years	Usually outlasts several solar systems. The slates themselves are brittle - fixing method matters.
Clay tile (incl. coppi, Frankfurter Pfanne)	50-100 years	Normally fine. Individual tiles crack; a good installer replaces rather than forces.
Concrete tile	40-60 years	Generally fine. Check for surface erosion and moss damage on older roofs.
Fibre cement / corrugated sheet	30-50 years	Older sheets may contain asbestos. Get this identified before anyone drills.
Standing seam metal	40-70 years	Excellent for solar - clamps on, no penetrations needed.
Bitumen felt (flat roof)	15-25 years	The one to watch. Often the shortest-lived layer on the house.
EPDM / single-ply membrane (flat)	25-35 years	Better, but a ballasted solar system adds weight - needs checking.

The pattern is clear. Pitched roofs with tile or slate are rarely the problem. Flat roofs and old sheet roofs are where the order of operations really matters.

If you have a flat roof with a bitumen covering that went on in the early 2000s, and you are considering a ballasted solar array, that is precisely the combination worth pausing on. The membrane may be nearing the end of its life, and a ballasted system is heavy and awkward to lift.

What to actually look for

You do not need to climb up there. Most of this is visible from the ground with a pair of binoculars, or from a loft hatch on a rainy day.

From outside:

Slipped, cracked or missing tiles and slates
Visible sagging along the ridge or between rafters
Heavy moss growth, especially in gutters (a sign tiles are shedding material)
Rusted or crumbling flashing around chimneys and roof windows
On a flat roof: ponding water, blisters, splits, or gravel washed into bare patches

From inside the loft, ideally during or after heavy rain:

Daylight coming through where it should not
Damp staining or rot on rafters and battens
Sagging felt or membrane between rafters
Any smell of damp

In the paperwork:

When was the roof last worked on? Previous owners' documents, or a neighbour's memory of the scaffolding, often settle the question.

If two or three of these show up, get a roofer to look. A straightforward roof inspection costs far less than what you would spend fixing the sequencing later.

The number that makes this worth reading

Here is the cost of getting the order wrong, using UK figures because they are the best documented - the shape of the maths is the same in Germany and Italy.

Removing and refitting solar panels for a reroof costs roughly £100 to £250 per panel.^[2] For a typical 10 to 12 panel home that is somewhere around £1,200 to £2,500, entirely on top of the roofing bill.^[3] If the original mounting rails have corroded, or the new covering is a different type from the old one, add another £300 to £600 for a fresh mounting kit.

For context on the roofing itself, a full re-roof on a standard three-bedroom semi in the UK typically runs £7,000 to £15,000^[4], with the covering driving much of the range: concrete tile around £85 to £170 per square metre, clay plain tile £110 to £210, and natural slate £140 to £280^[5].

So the penalty for doing it in the wrong order is not catastrophic - it is not another roof. But it is one to two thousand pounds or euros of pure waste, plus scaffolding twice, plus a system offline for a week or two, plus the small but real risk of something getting damaged in the handling.

Put the other way round: if your roof is genuinely near the end of its life, doing the roof first means one set of scaffolding, one set of site visits, and panels fitted onto a covering that will comfortably outlive them.

When "do the roof first" is the wrong advice

Worth saying plainly, because the roofing trade has an obvious interest here: most roofs do not need replacing before solar. A roof with 15 good years in it does not need pre-emptive work, and a few slipped tiles is a repair, not a re-roof.

Be a little sceptical if:

A solar installer recommends a full re-roof and happens to offer roofing too, without showing you evidence
The advice arrives without anyone actually inspecting the roof
The stated reason is vague - "it's quite old" - rather than specific defects

Ask for photographs. A competent roofer or installer will have been up there and will happily show you what they saw. "Three cracked tiles on the south slope and perished flashing at the chimney" is a real answer. "Your roof is 25 years old" is not.

Two things a good installer should do anyway

Regardless of age, any decent installation includes these, and it is fair to ask about them:

A structural sense-check. A solar array adds roughly 12 to 20 kg per square metre to a pitched roof. Most roofs built to normal standards take this without any trouble, but old, altered or lightly built roofs deserve a look - particularly where a previous owner has swapped a light covering for a heavy one.
The right fixings for your covering. Slate needs a different approach from interlocking concrete tiles, which needs a different approach from coppi. Panels should sit on hooks or clamps fixed to the rafters or battens, with the covering adjusted around them - never forced, never simply drilled through. Ask which mounting system they plan to use and why.

A five-minute decision tree

Is the roof under 10 years old with no known issues? -> Go ahead with solar.
Is it a slate, clay tile or metal roof under about 40 years old, in visibly sound condition? -> Almost certainly go ahead.
Is it a flat roof with a covering over 15 years old? -> Get it assessed before you commit. This is the highest-risk combination.
Is it 20+ years old, or showing two or more of the warning signs above? -> Roof inspection first. Then decide.
Are you likely to re-roof within about 10 years for any reason? -> Do the roof first and fit the panels afterwards. It is cheaper in one go.
Is it a fibre cement or corrugated sheet roof from before the mid-1990s? -> Have the material identified before anyone drills anything.

That is genuinely most of it. For the large majority of homes the answer is "your roof is fine, carry on" - but the minority where it is not is exactly the group that benefits most from asking the question early.

Then work out what the roof could actually do

Once you are satisfied the roof is sound, the next question is the interesting one: how many panels fit, what would they generate, and what would that be worth to you?

That is what our free Solar Roof Planner is for. Enter your address, trace your roof on a satellite image, and you get a realistic estimate of panel count, system size, yearly output, savings, payback period and a sense-check on whether a battery makes sense. No sign-up, no phone number, no follow-up call.

And if the answer turns out to be "roof first, panels next year", that is a perfectly good outcome too. Done in the right order, it costs less than doing it twice.