The decisive force on the roof is not the downward weight, but the upward wind suction – the storm wants to lift the modules off, not push them in. This is exactly what systems are built for: with calculated mounting, reinforced edge and corner areas and tested components. Professionally installed systems routinely survive Swiss storms; your contribution is limited to looking from the ground afterwards. (As of: July 2026)
Key points in brief
- Wind doesn't just push – it sucks: When flowing over the roof, suction is created which wants to lift off the modules. The mounting is designed for this, not against weight.
- Roof edges and corners are the storm hotspots – there the specialist company plans denser mounting or deliberately leaves a gap to the edge.
- On the flat roof, ballast holds instead of screws – the mounting system is aerodynamically shaped and weighed down with a calculated weight.
- After a severe storm, the same rule as always applies: visual inspection from the ground, a look at the monitoring – only the professional belongs on the roof.
- Loose modules, shifted rows or hanging cables are an immediate case for the specialist company, not an observation post.
The underestimated force: Why suction is more dangerous than pressure
Anyone who thinks of storms and roofs thinks of pressure – in fact, the wind on the roof mainly works the other way around: If it flows over the building, a suction is created on the leeward side and over edges, which pulls on the roofing and modules like on an aeroplane wing. In the structural analysis, the exciting variable is therefore not the system weight, but this lifting force – the mounting does not have to carry the modules, it has to hold them fast.
This also explains why storm damage to solar systems is almost never «broken modules», but rather – where it occurs – mounting failure: The wind finds a too weakly clamped corner, levers there and works its way forward. And it explains why storm safety is decided on the day of installation, like so much about the system: It lies in the number and position of the mounting points, not in an accessory that you buy later.
How systems are built against storms
Calculated mounting instead of feeling. The number of roof hooks and clamps per module follows the wind load of the location, the building height and the roof geometry – the manufacturers of the mounting systems provide the design rules, the planner applies them. The basis is provided by the SIA 261 standard: Even for the least windy locations of the Swiss Plateau, it applies a reference dynamic pressure of 0.9 kN/m² – this corresponds to hurricane strength, i.e. gusts of well over 100 km/h –, and correspondingly more in exposed and alpine locations (as of: July 2026). The modules themselves are also tested for suction: The standard test according to IEC 61215 loads them with 2,400 Pascal in both directions. A more exposed location means denser mounting; this is planning routine, as with the snow load, only with an inverted force arrow.
Edge and corner zones with special treatment. The suction is not evenly distributed – it is strongest at roof edges, ridges and corners. Professional planning reacts to this with denser mounting points in these zones or with a deliberate distance of the module surface to the roof edge. The free strip at the edge, which sometimes strikes laypeople as «wasted space», is often exactly that: planned storm safety.
Clamping in the right place. Modules may only be clamped in the areas defined by the manufacturer – outside of this, their tested load capacity drops significantly. This is one of the points where careful differs from rushed installation, without it being seen from the street.
Flat roof: Ballast and aerodynamics. On the flat roof, drilling is usually not used, but rather weighting down: The mounting system is aerodynamically shaped (closed rear walls, low angles of incidence) and covered with calculated ballast – enough so that nothing moves, no more than the roof can bear. Here too: Edge and corner zones receive more weight.
What you should do after a storm – and what not
After a severe storm, the proven pattern from the annual check applies, just event-related:
1. Visual inspection from the ground – once around the house, with binoculars if necessary: Are the module rows sitting straight? Is a cable hanging? Is there something lying on the surface (branches, neighbour's trampoline)? 2. Look at the monitoring – is the system producing normally, are there new fault messages? A string that has been silent since the storm is a finding. 3. In case of a finding: specialist company, immediately. Shifted modules and loose parts are not observation posts – what the storm has levered up, the next one will take. Avoid the area under the affected roof section until the inspection. 4. Documenting – photos with date, for the insurance claim: Storm damage is typically a case for the building insurance, and the process is similar to a hail case.
And the counter-list is short and well-known: do not go onto the roof. Not to check, not to «press down», not for a photo. After a storm, the roof is the most dangerous place on the property – loose parts, weakened mountings, and you don't know where.
Exposed locations: When storms become a planning topic
For most roofs on the Swiss Plateau, storm safety is resolved routine. Three constellations deserve heightened attention during planning – and are good test questions for the consultation:
- Exposed locations: Detached houses on hilltops and ridges, locations with known foehn or bise wind corridors, tall buildings.
- Large flat roofs: The larger the area, the more important the zoned ballasting – and the more worthwhile a look into the ballast calculation of the quote.
- Old roofing: The best module clamp is of little use if the roof hook sits in crumbly timber – the roof condition needs to be checked anyway, doubly so in windy locations.
The test question for all three is the same and simple: «Is the mounting designed for our wind load – and how?» A company that answers this with zones, point distances and system specifications is planning; one that says «that will hold» is hoping.
After every major storm, our telephone rings – and the balance has been the same for years, reassuring and instructive in both directions. Reassuring: On professionally installed systems we almost never find structural damage after Swiss storms – the systems are designed for more than our weather conditions deliver. Instructive: The findings that do exist are almost always in the same places – edge rows with a saved mounting point, clamps outside the manufacturer's zone, flat roof ballast that was distributed «by experience» instead of by calculation. In other words: The storm does not test the modules, it tests the installation. Our advice to anyone planning a system or taking over someone else's: Ask to be shown the mounting design. It is a piece of paper – and it is the piece of paper that counts in the foehn storm.
Frequently asked questions
Can a storm rip modules off the roof?
With professional installation designed for the location's wind load, this is the great exception – the mounting systems are calculated for the suction forces. The documented cases are usually due to installation errors: too few mounting points, clamps in the wrong place, missing edge distance.
Do I have to secure my system before an announced storm?
No – a correctly installed system needs no storm preparation, and short-term DIY measures on the roof would be more dangerous than the storm. Only the usual is sensible: clear away loose objects on the ground, do a visual inspection after the storm.
Who pays if the storm damages the system?
Like hail, storms are classified as natural hazard damage and are typically covered by building insurance – provided the system has been registered. Document the damage with photos and report it promptly; the details on cover are in the insurance guide.
Are flat roof systems more susceptible to storms?
Not if executed correctly – they are secured differently (aerodynamic mounting system plus calculated ballast instead of screwing), but according to the same wind load rules. It only becomes critical if the ballast was estimated instead of calculated – a point that should be verifiable in the quote.
My neighbour had damage – should I have my system checked?
A storm that leaves damage in the neighbourhood is a good reason for your own visual inspection and a look at the monitoring – and in the case of any finding, for a professional inspection. Without a finding, the documented self-inspection is sufficient; note the date in the system dossier.
Free initial consultation
Built for the foehn storm, not for the brochure.
We design every mounting for the wind load of your location – with zone planning and documented design. And after the storm we are there, even for systems that do not come from us.
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Sources: SIA 261 standard «Actions on structures» (reference dynamic pressure from 0.9 kN/m², Appendix E); IEC 61215 test standard (suction load test 2,400 Pa); mounting system manufacturers (wind load design basics); empirical values from the installation and storm inspection practice of ecoEn GmbH, Zurich region. (As of: July 2026)
Last updated: 9 July 2026 · Author: ecoEn editorial team
