Why the roof comes first
Rooftop solar panels are designed to stay in place for decades. The roof underneath them usually is not. If the roofing material wears out a few years after the panels go up, the whole array has to be taken down, stored and reinstalled so the roof can be replaced. That removal-and-reinstall work is a separate job with its own cost, and it can also interrupt your solar production for weeks. Checking the roof before you sign a solar contract is one of the simplest ways to avoid an expensive surprise later.
This checklist is meant to help you have a better conversation with a roofer and with solar installers. It is not a substitute for an on-site inspection by a qualified professional.
1. How old is the roof, and what is it made of?
Start with the basics: when was the roof last replaced, and what material is it? Your home purchase paperwork, previous permits or the roofer who did the work may have the answer. Different materials have very different expected lifespans, and the manufacturer's warranty documents usually state what the product was designed for.
- Asphalt shingles are the most common roof for residential solar, and most installers are comfortable mounting on them.
- Metal roofs, especially standing-seam types, can often take clamp-on mounts that avoid drilling through the roof surface.
- Tile, slate and wood shake roofs can carry solar, but mounting is more specialised and breakage during installation is a real risk. Ask installers directly how often they work on your roof type.
- Flat or low-slope roofs typically use tilted racking, which changes the layout and wind-load considerations.
A useful rule of thumb: compare the remaining life of the roof with the period you expect to keep the panels. If the roof is clearly closer to the end of its life than the beginning, ask for a quote to replace it before the panels go on.
2. Look for visible warning signs
From the ground, with binoculars, or in photos taken by a roofer, look for curling or missing shingles, granules collecting in gutters, sagging areas, rust on metal panels, cracked tiles, or patched sections. Inside, check the attic for water stains, daylight showing through boards, or damp insulation. Any of these is a reason to have the roof assessed before mounting anything on it.
3. Ask about the roof structure
Panels and racking add weight, and they also change how wind and snow load the roof. In many places the permit process requires the installer to confirm that the structure can carry the system, and some older homes need reinforcement. Ask each installer whether they will review rafter size and spacing, whether a structural engineer's letter is needed for your home, and who pays for any reinforcement that turns out to be necessary.
4. Check the usable roof area
Not every square foot of roof can hold panels. Vents, chimneys, skylights and plumbing stacks take up space, and many local fire codes require clear pathways and setbacks along ridges and edges so firefighters can move safely. A roof that looks large from the street can end up with a smaller usable area than expected. Ask installers to show you a layout drawing with the setbacks marked, not just a total system size.
5. Decide whether to re-roof first
If your roof needs replacing soon, there are a few common approaches:
- Re-roof, then install solar. This is the cleanest option. Some homeowners coordinate the two jobs so the roofer can install flashing or mounting points in a way the solar installer is happy with.
- Re-roof only the sections that will carry panels. This can make sense when one plane of the roof is in worse shape or faces the sun, but matching old and new materials can be tricky.
- Delay solar. If budget does not allow both, it can be better to wait than to put panels on a roof that will need to be stripped soon.
6. Understand who warrants what
Drilling through a roof to attach mounts can affect the roofing warranty. Ask the installer how penetrations are flashed and sealed, whether they offer a workmanship warranty covering leaks around mounts, and for how long. Ask your roofer whether their warranty stays valid after a solar installation. Get the answers in writing, because the roofer and the solar company may each point to the other if a leak appears later.
7. Plan for future roof work
Even a new roof may need repairs during the life of the panels. Ask installers what they charge to remove and reinstall the system, whether that price is fixed in the contract, and whether they will still be the right company to call years from now. If the installer may not be around, find out whether other local companies service that brand of racking and equipment.
Quick checklist before requesting quotes
- Roof age and material written down, with warranty documents if you have them.
- Photos of the roof surface and the attic underside.
- A roofer's opinion on remaining life, if the roof is not new.
- Questions for installers about structure, setbacks, flashing method and warranty.
- A written price for future removal and reinstallation of the array.
Getting the roof question settled first does not make solar cheaper on day one, but it removes one of the most common reasons a solar project costs more than expected over its lifetime. For more planning help, see our homeowner solar FAQ and the guide to choosing an installer.