Should you replace your roof before solar?

Solar panels can stay on a roof for 25 years or more. If your roof needs replacing in five or ten years, the panels will have to come off and go back on, which adds cost and hassle. Deciding the order of the two projects up front can save you money.

Rules of thumb on roof age

A common guideline is that your roof should have at least as many years left as you expect to keep the panels, or close to it. In practice:

• Roof under about 10 years old, in good condition: usually fine to install solar now.
• Roof in the middle of its life: get a roofer to inspect it. Small repairs may be enough.
• Roof near the end of its life: replace it first.

How long a roof lasts depends on the material, the quality of the original install, ventilation and exposure. Asphalt shingles usually last much less time than metal. Signs a roof is near the end include curling or cracked shingles, lots of granules in the eavestroughs, bare spots, soft decking and past leaks.

A good solar installer will look at your roof during the site visit and tell you if they have concerns. Some won't install on a roof in poor shape. If an installer has no opinion at all on a worn roof, be cautious.

Removing and reinstalling panels later

If you install solar and then need a new roof, the panels must be disconnected, removed, stored and reinstalled. An electrician or solar installer usually does this, and the electrical reconnection may need a new permit and inspection.

Canadian price data for this work is limited. US cost guides put it at roughly US$200 to US$300 per panel, or about US$2,800 to US$4,800 for a typical 14 to 16 panel system, not counting the roof itself. Canadian prices will vary with your installer, the system size, roof access and whether any parts need replacing. Ask your installer what they charge for removal and reinstallation, and get it in writing.

Removing and reinstalling can also affect warranties. Check whether your workmanship warranty survives if another company handles the work.

When it makes sense to replace first

• Your roof is likely to need replacing within the next 10 years or so
• You have had leaks or visible damage
• You were planning a roof replacement anyway

Doing both projects close together means the roof under the panels is new, the mounting points go into fresh decking, and you avoid paying for removal later.

When it makes sense to wait

• The roof is fairly new and in good condition
• An inspection finds only minor repairs

Don't replace a sound roof just because you are adding solar. That spends money for no benefit.

Coordinating the roofer and the installer

When you do both, the order and communication matter.

1. Get solar quotes first, so you know the system size and layout before roof work starts.
2. Ask both trades about flashing and mounts. Some roofers want to install specific flashing or blocking for the solar mounts. Some solar installers use their own approved method.
3. Plan conduit routes for wiring, so you don't have unnecessary new holes.
4. Check warranties. Ask the roofer whether solar mounts affect their warranty, and ask the solar installer whether their roof penetration warranty depends on the roofer's work.
5. Schedule close together. Some homeowners have the roofer and installer on site within days of each other.

A few companies do both roofing and solar. That can simplify warranties, but compare their prices with separate quotes.

Structural checks

Panels and racking add weight, and in Canada the roof must also carry snow. Many municipalities require structural information for rooftop solar. Toronto, for example, requires calculations from an Ontario-registered engineer covering the roof framing and attachments for systems over 5 square metres. A roof replacement is a good time to fix any weak or damaged decking.

Shingle roofs

Asphalt shingle roofs are the most common in Canada and the easiest to install on. Mounts are bolted into the rafters through flashing that sits under the shingles. Ask for the number of penetrations and the sealing method.

Metal roofs

Metal roofs last much longer than shingles, which makes them a good match for solar's long life.

• Standing seam metal can often take clamps that attach to the raised seams with no holes through the roof.
• Corrugated or exposed-fastener metal usually needs mounts that attach through the roof with sealed brackets.

If you are replacing a roof and plan to add solar, it is worth getting a metal roof quote. It usually costs more upfront, so weigh it against how long you plan to stay in the home.

Insurance and paperwork

Tell your home insurer when you add solar and when you replace the roof. Keep inspection certificates, permits and warranties for both. See solar and home insurance.

Next step

Check your roof for an estimate, and read is my roof suitable for the full list of factors.

Common questions

How old is too old for a roof before installing solar?

If your roof is likely to need replacing within about 10 years, replacing it first usually makes sense. Get a roofer's inspection if you are unsure.

How much does it cost to remove and reinstall solar panels?

US cost guides put it at roughly US$200 to US$300 per panel. Canadian prices vary, so ask your installer for a written price before you sign.

Do solar panels void my roof warranty?

They can if the mounting method is not approved by the roofer or shingle manufacturer. Ask your roofer before installation and get the solar installer's roof penetration warranty in writing.

Is a metal roof good for solar?

Yes. Metal roofs last a long time, and standing seam metal can often take clamps that need no holes. It usually costs more upfront than shingles.

Sources

• Fixr: Cost to remove solar panels to replace a roof (US data)
• City of Toronto: Building permit guide for solar collectors