In the vast majority of cases, yes. An on-roof solar system adds extra weight to the roof, which an intact, standard-compliant roof can generally bear without any problems – the additional load is low compared to snow and wind loads, which the roof has to withstand anyway. The specialist company checks the statics as part of the planning; for special constructions, a structural engineer is brought in. (As of: July 2026)
Key points in brief
- A solar system adds extra weight to the roof – but a moderate one compared to snow loads.
- With intact, standard-compliant roofs, statics are rarely the problem.
- The specialist company checks the roof structure, rafters and fastening as part of the planning.
- A structural engineer is consulted for special constructions, large systems or in case of doubt.
- Often more important than the sheer weight is the correct fastening – the forces from wind and snow.
How heavy is a solar system anyway?
The concern about the roof load is understandable – something is going on the roof that was not there before. In context, however, it is quickly put into perspective. An on-roof system consists of the modules, the mounting structure with which they are fastened, and the wiring. As a guideline value, this adds around 15 to 25 kilograms per square metre to the roof (As of: July 2026) – glass-glass modules are more at the upper end of this range. That is moderate, especially compared to the loads that a Swiss roof has to bear anyway.
Because the decisive measure of comparison is not the weight of the system itself, but the snow load. The SIA 261 standard sets a minimum value of 0.9 kN/m² for the snow load in Switzerland – which corresponds to around 90 kilograms per square metre – and scales it up according to altitude: at around 800 m above sea level, the calculated value is already around 2.5 kN/m², i.e. about 250 kilograms per square metre. A roof that is designed for this will generally bear the 15 to 25 kilograms of the system as a small additional load within its reserves. Anyone who imagines how much wet snow can lie on a roof in February has the right order of magnitude in mind.
Why are the statics rarely the problem?
Because roofs are built with reserves. The building regulations require a roof to safely absorb the snow and wind loads expected at the location – and this design includes safety margins. An evenly distributed, comparatively light solar system generally falls within these existing reserves.
This does not mean that the question is skipped – it means that for an intact, standard-compliant roof, it is usually answered reassuringly. More critical than the sheer weight are two other things: the condition of the roof and the fastening. A dilapidated roof that is getting on in years is more a case for renovation before the system than a statics problem in the strict sense. And the fastening determines whether the system can also withstand the forces acting not downwards, but upwards and sideways – more on this in a moment.
What does the specialist company check – and when is a structural engineer brought in?
The assessment of the roof load is part of any serious planning, not an optional extra. The specialist company looks at several things during the site visit:
| Check point | What matters |
|---|---|
| Roof structure & construction | Rafter spacing, framework, condition of the wood |
| Roofing | Tiles, sheet metal, Eternit – condition and fastening option |
| Snow and wind zone | location-dependent load assumptions |
| Fastening type | how the mounting structure transfers forces into the framework |
Simplified overview, As of: July 2026. The specific assessment at the property is decisive.
For an ordinary single-family home with an intact pitched roof, this professional assessment is usually sufficient. A structural engineer is specifically called in if there is a reason: for unusual roof constructions, visible weaknesses in the framework, very large systems, flat roofs with elevation and corresponding wind attack surface – or simply when the specialist company has doubts during the site visit. This step is not an alarm signal, but good practice: it is better to calculate once too often than to have a system on a framework that has only been presumed.
Whether your roof is fundamentally suitable can be roughly assessed in advance via the official portal sonnendach.ch – but the binding assessment of statics and fastening is only provided by the on-site site visit, which is part of every path to the system.
Not just the weight: wind and fastening
A common misconception is to think only of the downward pressing weight when it comes to the roof load. In practice, the wind load is often the more demanding variable. Wind creates suction on the modules – it wants to lift the system, not press it down – and precisely at roof edges and corners, these forces can be considerable. The fastening must therefore not only hold the weight, but also securely anchor the system to the framework in the event of a storm.
That is exactly why the type of fastening is a central planning point: the mounting structure must transfer the forces into the framework at the right places – usually at the rafters – and the number and distribution of the fastening points depend on the wind and snow zone of the location. A correctly planned and installed system withstands both; a poorly fastened one can become a problem in a storm, regardless of how load-bearing the roof itself is. So the weight is rarely the hurdle – professional anchoring is the actual engineering feat on the roof.
«Will my roof even hold this?» is one of the most frequent concerns in the initial consultation – and almost always we can ease it. We then briefly calculate: what lies on a roof as wet snow in winter is a multiple of what our system permanently adds to it, and the roof is built for this. Nevertheless, we look closely at every site visit – not because of the weight, but because of the condition and the fastening. Where the framework is fine, the matter is clear. Where we have doubts – an idiosyncratic construction, a conversion, visibly tired wood – we call in a structural engineer before we place a screw. This is one of the moments that shows a reputable business: not in declaring every roof load-bearing, but in having it calculated when in doubt rather than hoping.
Frequently asked questions
How much weight does a solar system add to the roof?
As a guideline value, around 15 to 25 kilograms per square metre – modules, mounting structure and wiring together, evenly distributed. Compared to the snow load for which a Swiss roof is designed according to the SIA 261 standard (at least around 90 kg/m², in higher locations a multiple), this is low – the system generally falls within the existing load-bearing reserves of an intact roof.
Does my roof need to be reinforced for a solar system?
In the vast majority of cases, no. Standard-compliant, intact roofs bear an on-roof system without reinforcement. A closer inspection or measure is only necessary for special constructions, weakened frameworks or very large systems – the specialist company assesses this, in case of doubt with a structural engineer.
Who checks whether my roof will support the system?
The specialist company as part of the planning – it assesses the roof structure, condition and fastening option during the on-site site visit. For unusual roofs, doubts or large systems, it calls in a structural engineer. This check is part of every serious planning.
Is the wind load really more important than the weight?
Often yes. Wind creates suction on the modules and wants to lift the system – especially at roof edges and corners. The fastening must safely transfer these forces into the framework. Professional anchoring is therefore more decisive than the pure question of weight, which is rarely critical with intact roofs.
Can I put a solar system on an old roof?
On an intact old roof, yes – age alone is not an obstacle, the condition counts. If the framework or the roofing is weakened, renovation belongs before the system, so that the modules do not have to be dismantled again for a roof renewal in a few years' time. The specialist company clarifies the condition during the site visit.
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Safely onto the right roof.
We assess statics, condition and fastening during the site visit – and call in a structural engineer in case of doubt before we plan. So that the system holds securely, in snow as in storms.
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Swissolar-certified specialist company · ESTI installation authorisation (Art. 14 NIV) · in Zurich since 2017 · over 150 systems completed · a personal answer from the specialist company, no call centre
Sources: SIA 261 standard «Actions on structures» (minimum snow load value 0.9 kN/m², altitude-dependent calculation); Swissolar (planning and fastening principles); industry guideline values for the weight per unit area of on-roof systems (As of: July 2026); empirical values from the planning and mounting practice of ecoEn GmbH, Zurich region.
Last updated: 9 July 2026 · Author: ecoEn editorial team
