The installation of photovoltaic systems on industrial rooftops has experienced exponential growth in Spain. However, one of the most critical and often underestimated aspects is the correct sizing and structural verification of the solar mounting structures.
A poorly calculated structure can cause deformations, wind damage, overloading of the roof, or even irreversible damage to the industrial building.
In this guide we explain the fundamental technical criteria for designing and verifying rooftop solar structures , including wind loads, snow loads, self-weight, ballasted systems and the most frequent errors that compromise the safety of the installation.
Why is it essential to check the structure before installing solar panels?
The roof of an industrial building does not always have sufficient capacity to support a photovoltaic plant.
Before installing any system, it is necessary to analyze:
- Strength of the supporting structure.
- State of conservation of the roof.
- Allowable overloads.
- Exposure to wind.
- Snow accumulations.
- Compatibility with existing waterproofing.
Structural verification allows us to guarantee:
- Safety of people.
- Installation safety.
- Regulatory compliance.
- Protection of long-term investment.
Applicable regulations in Spain
The calculation of solar structures should be carried out considering primarily:
- Technical Building Code (CTE).
- Eurocode 1 (Actions on structures).
- Eurocode 3 (Steel structures).
- Eurocode 9 (Aluminum structures).
- UNE standards applicable to photovoltaic systems.
- Specific requirements of insurers and regulatory bodies.
In addition, each autonomous community may require supplementary technical documentation for large-scale industrial projects.
Loads that affect a photovoltaic structure
Structural calculations must consider the combination of several simultaneous actions.
1. Self-weight of the installation
Includes:
-
- Solar panels.
- Structural profiles.
- Screws.
- Fastening elements.
- Trays and conduits.
Typical values:
| Element | Approximate weight |
|---|---|
| PV Modules | 12-15 kg/m² |
| Aluminum structure | 2-8 kg/m² |
| Ballasted system | 10-50 kg/m² |
The total load can vary greatly depending on the chosen solution. Learn more about ballast calculations here.
2. Wind loads
Wind is usually the most decisive factor in photovoltaic roofs.
Factors that influence:
-
- Basic wind speed of the area.
- Building height.
- Urban or open environment.
- Module tilt.
- Distance to edges and corners.
The most critical points are usually found in:
-
- Corners.
- Perimeters.
- Level changes.
An insufficiently designed structure can suffer from:
-
- Lifting.
- Anchor fatigue.
- Breakage of fixings.
- Detachment of modules.
Learn more about wind zone calculations here.
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3. Snow loads
Although Spain does not have extreme levels in most regions, there are areas where snow is a significant factor.
Especially in:
-
- Castilla y León
- Aragón
- Navarra
- Asturias
- Mountain areas and high altitudes.
The accumulation of snow can generate stresses far exceeding the installation’s own weight.
4. Thermal expansion
Metal structures experience movement due to temperature variations.
Therefore, it is essential to plan ahead:
-
- Expansion joints.
- Maximum profile lengths.
- Fixing systems compatible with thermal movements.
Anchored systems versus ballasted systems
anchored systems
Advantages:
-
- Less weight on deck.
- Improved wind resistance.
- Less need for ballast.
Disadvantages:
-
- They require controlled drilling.
- They need reliable sealing systems.
They are common in corrugated sheet metal roofs and sandwich panels.
Ballasted systems
Advantages:
-
- They do not pierce the waterproofing.
- Quick installation.
Disadvantages:
-
- They significantly increase permanent loads.
- They demand a thorough structural inspection.
A common mistake is to assume that the deck will automatically support the additional weight of the ballast.
How to check if an industrial roof can support a photovoltaic installation
A key step in the process of verifying and sizing rooftop solar structures is structural calculation.
The process usually includes:
1. Data collection
-
- Original plans.
- Cover type.
- Light between straps.
- Structural materials.
- State of conservation.
2. Modeling
A structural model is created considering:
-
- Permanent actions.
- Variable stocks.
- Normative combinations.
3. Robust verification
It is verified:
-
- Straps.
- Trusses.
- Porticoes.
- Unions.
- Anchors.
4. Verification of deformations
It is not enough for the structure to withstand the pressure.
It should also limit:
-
- Arrows.
- Vibrations.
- Excessive movements.
Most common mistakes in rooftop photovoltaic installations
Error 1: Failure to review the existing structure
Many industrial roofs are decades old.
Actual capacity may differ significantly from original plans.
Error 2: Copying calculations from another project
Each ship has:
-
- Different geometry.
- Different climate zone.
- Different exhibition.
There are no universal calculations.
Error 3: Ignoring border zones
The greatest wind suctions usually occur in:
-
- Corners.
- Perimeters.
- Coronations.
Sizing the entire plant with the same criteria can generate localized failures.
Error 4: Overloading the deck
Adding more ballast does not always mean greater safety.
It can cause:
-
- Excessive overloads.
- Permanent deformations.
- Structural risk.
Error 5: Not considering watertightness
Leaks usually appear years after installation.
Therefore, it is essential to use systems specifically designed to guarantee waterproofing.
Download our free leak-proofing guide.
Error 6: Using incompatible components
The wrong combination of materials can produce:
-
- Galvanic corrosion.
- Loss of resistance.
- Reduction of useful life.
For this reason, many modern structures use structural aluminum combined with specific screws and protective elements.
Safety checklist before installing solar panels
Before starting any project, it’s advisable to check:
- Structural calculation performed.
- Wind check.
- Snow check.
- Review of permissible loads.
- Study of fixations.
- Waterproofing verification.
- Material compatibility.
- Regulatory compliance.
- Maintenance plan.
Frequently Asked Questions (FAQ) on sizing and verifying the safety of solar structures on industrial roofs
How much weight does a photovoltaic installation add to an industrial roof?
Normally between 15 and 30 kg/m², although ballasted systems can far exceed these values.
What is more critical, the wind or the snow?
In much of Spain, wind is usually the most unfavorable design factor, especially on large industrial roofs.
Can panels be installed in any industrial building?
Not always. It is essential to verify the load-bearing capacity of the existing structure.
Is it mandatory to perform a structural calculation?
Although it will depend on the project and the applicable regulations, from a technical and professional responsibility point of view it is highly recommended to guarantee safety.
Alusín Solar and dimensioning solar structures on the roof
The success of a rooftop photovoltaic installation for industrial buildings depends not only on the solar panels themselves. The safety, durability, and profitability of the project are directly related to the correct sizing of the support structure.
Properly analyzing wind, snow, self-weight and ballast loads allows you to avoid incidents, reduce risks and maximize the useful life of the installation.
Companies that incorporate specific structural calculations and fixing systems designed for each roof achieve safer, more efficient projects built to withstand decades of service. At Alusín Solar, we can size the rooftop solar structures you need. Request a quick technical consultation .
