Roof survey before solar: shade, salt air and flat roofs in the Algarve

Why the roof survey matters

Algarve houses often have terraces, chimneys, pergolas, palms, neighbouring walls, satellite dishes and architectural parapets. None of these are unusual, but each can reduce output or complicate installation. PVGIS can estimate production for orientation and tilt, while IPMA climate information helps frame local solar and weather conditions. The missing piece is the site survey: where shadows fall, how installers reach the roof, what fixing method protects waterproofing, and whether the electrical route is sensible.

A weak quote treats the roof as empty space. A strong quote treats it as a building envelope that must keep water out for decades. This is especially important on flat or low-slope roofs, where ballast, wind loads, drainage and membrane protection matter. For coastal properties, corrosion-resistant components and tidy cable management are not cosmetic details; they influence reliability.

Orientation is not the whole story

South-facing roofs are useful, but east-west layouts can also work well when the home has morning and afternoon loads. A west-facing string may support late-day cooling better than a perfect noon peak. The question is not “which direction is ideal in theory?” but “which layout produces usable electricity when this household consumes it?” Ask the installer to compare options rather than defaulting to the largest single plane.

Maintenance and monitoring

Panels usually require little routine care, but “little” does not mean “none”. Dust, pollen, sea salt, bird activity and storm debris can affect output. Monitoring helps spot a drop, but only if the owner knows what normal production should look like. Ask who receives alerts, how underperformance is diagnosed, and whether annual or post-storm inspection is available. Remote owners should decide who can grant roof access and who approves small repairs.

Do not let installers drill or route cables without explaining waterproofing. Ask for photos before and after installation, especially on flat roofs. If the home will be sold or rented, these photos become part of the property file and can reassure future buyers or managers.

What to request in writing

Roof survey checklist

• Photos of each roof plane and proposed panel zones
• Shade assessment for chimneys, trees, walls and equipment
• Mounting and waterproofing method
• Cable route to inverter and consumer board
• Access and safety plan for installation and maintenance
• Production estimate by month and by orientation
• Explanation of any optimiser or microinverter recommendation

Common mistakes

Avoid these

• Using satellite images instead of a physical survey for a complex roof
• Ignoring winter shadows because the viewing happened in summer
• Covering every possible space and leaving no access path
• Installing near drains or roof details without a maintenance plan
• Assuming panel warranty solves workmanship or waterproofing issues

Frequently asked questions

Do I need optimisers? Sometimes, especially with partial shade or multiple orientations, but ask for the reason and expected benefit. Is a flat roof easier? It can be, but ballast, wind and waterproofing must be handled carefully. Should I clean panels often? Usually not obsessively, but coastal salt and dust make monitoring useful. Can a small shaded section ruin the whole system? It depends on string design and equipment.

For older properties, also ask whether the installer has considered roof age, access for scaffolding and future maintenance. A panel layout that blocks a terrace drain, makes chimney service difficult or hides a fragile tile detail can create costs later. The best proposals explain why some roof areas are left empty. That restraint is often a sign of professional judgment rather than lost opportunity.

Bottom line

The roof decides whether a solar project is elegant or troublesome. Use PVGIS and IPMA for production and climate context, but insist on a physical survey, a clear mounting plan and documented maintenance responsibilities. A slightly smaller system on the right roof area can outperform a larger system squeezed into the wrong places.

A final practical step is to ask the installer to write down the operating assumptions in homeowner language: what runs in daylight, what remains on the grid, who checks monitoring, and what changes if the family later adds a battery, heat pump or electric car. This paragraph may sound administrative, but it prevents many disputes because everyone can see whether the project was designed for the real house or for a generic sales spreadsheet.

A final practical step is to ask the installer to write down the operating assumptions in homeowner language: what runs in daylight, what remains on the grid, who checks monitoring, and what changes if the family later adds a battery, heat pump or electric car. This paragraph may sound administrative, but it prevents many disputes because everyone can see whether the project was designed for the real house or for a generic sales spreadsheet.

A final practical step is to ask the installer to write down the operating assumptions in homeowner language: what runs in daylight, what remains on the grid, who checks monitoring, and what changes if the family later adds a battery, heat pump or electric car. This paragraph may sound administrative, but it prevents many disputes because everyone can see whether the project was designed for the real house or for a generic sales spreadsheet.