Rooftop Solar Mounting Structures: How to Choose the Right One?

Choosing the right mounting structure for rooftop solar systems is crucial for optimal performance and efficiency. Whether it’s for a home, a commercial carport, or a ground setup, the type of structure you choose is key to your solar project’s success.

Consider factors like local weather, building structure, and solar panel orientation for maximum sunlight exposure. The site’s location and construction details directly impact the solar system’s effectiveness and longevity. To balance functionality and efficiency, carefully select a photovoltaic (PV) mounting structure that suits your site’s unique conditions and requirements.

In today’s read, we’ll guide you through the main components for different types of roofs to help you find the best solution for installing solar panels.

rooftop solar mounting structures

What are Solar Roof Mounting Solutions?

Solar panel mounts and racks are crucial for securing solar plants, ensuring stability and long-term effectiveness. These mounting systems allow adjustments in panel tilt, tailored to latitude, seasons, or even time of day to maximize solar energy production. The most common sites for mounting solar panels are rooftops or the ground, each requiring specific solar roof mounts or ground-mount options.

Roof-mounted solar panels are often supported by a visible metal racking system, providing secure placement and optimal positioning for capturing solar energy. According to PV Solar First, metal racks play a key role in the structural setup of solar panels, whether on roofs or in ground-mounted systems.

Mounts and racking typically represent around 10% of the total cost of an average solar system. For a $10,000 solar system, the racking system would cost approximately $1,000. Prices can vary based on racking type, equipment quantity, and installation labour costs.

The most common method of solar module mounting uses solar panel mounting brackets. These heavy-duty brackets, usually made from materials like stainless steel or aluminium, ensure installation longevity and stability. All solar racking and mounting products, whether for rooftop or ground installation, must meet strict guidelines for durability and structural integrity to withstand high winds and severe weather conditions.

How are Solar Panels Mounted to Roof?

Solar panel racking equipment is carefully crafted to secure and enhance your solar panel setup, consisting of three key components: roof fixings, module clips, and mounting bars. Each part plays a vital role in ensuring your solar panels are well-supported and positioned to capture the utmost solar energy.

  • Roof Fixings: These are the foundational elements that attach directly to your roof, using drills to create holes for secure placement. To prevent water ingress, these holes are surrounded by ‘flashing’—a protective layer, typically made of plastic or metal, that rests between the roof tiles. It’s worth noting that the type of roof fixing used varies depending on the roof material, whether it’s clay tile, metal, or a flat surface. Further details for specific considerations for various roof types can be beneficial.
  • Module Clips: These clips connect the roof fixings to the mounting bars and provide support for the solar panels. They come in various sizes and shapes to efficiently fit each angle and corner of the solar panel.
  • Mounting Bars: Once the roof fixings are secured, they attach to the mounting bars via module clips. These bars are crucial for supporting the solar panels. While railless options exist, traditional bars are common due to their versatility in accommodating most roof angles and the widespread installer familiarity with this system.

What are the Different Types of Solar Mounting Structures for Roofs?

Mounting solar panels to a roof involves precise engineering and careful consideration of both the roof’s capability to bear weight and the ideal alignment for solar exposure.

Flat roof mounting systems

When it comes to flat roof solar, we’re talking about setting up solar panels on a roof with a pitch of around 1–10 degrees. The main worry with flat roof setups is the roof’s weight limit. Here are three common types of solar mounts for flat roofs:

Metal Triangular Elevated Mounting Systems

Metal triangular elevated solar mounting systems are crafted for flat roof structures to securely hold solar panels in place. They can be installed directly on the roof or on pre-made concrete cement blocks. These frames, in the shape of a triangle, are versatile, accommodating different panel types and enabling angle adjustments (from 5° to 45°) for optimal solar panel performance.

Ballasted Racking Systems

These systems are a great option for flat roofs with a slope of under 7 degrees, as they usually avoid the need to drill into the roof, preventing potential leaks. This method involves adding weights to secure solar panels in place, adding an extra load of around 3-7 pounds per square foot (PSF) to the roof’s solar structure.

For buildings where the roof structure may struggle with this added weight, mechanical attachments provide an alternative way to secure the system without overloading the roof. Ballasted racking systems typically allow solar modules to be installed with a tilt of 5, 10, or 15 degrees, optimising the angle between the solar panels and the sun’s rays for maximum energy production.

Sloped Roof Solar Mounting Systems

Most houses have sloped roofs, requiring solar panel mounts to adjust panels to an inclined position. Manufacturers offer the following options:

Rail-Less Mounting

Rail-less mounting systems are gaining popularity. They include rail brackets, EPDM rubber, and screws that directly fix solar panels to the sloped roof without rails.

Railed Mounting

Railed mounting systems are one of the most common rooftop solar mounting structures. They consist of a set of rails attached to the roof, with each panel secured to the rails via clamps. The rails are then anchored to the roof with bolts and screws.

Shared-Rail Mounting

Shared-rail mounting systems function similarly to railed systems but require fewer rails. For two solar panels, a railed system typically needs four rails, while a shared-rail system needs only three. The panels share a central rail and use two edge rails, reducing installation time, cost, and the number of roof penetrations.

Metal Roof Solar Mounting Systems

For commercial solar panel mounting solutions, metal roof systems are a common choice.

Trapezoidal Roof Mounting

Trapezoidal metal roofs are a common sight on many commercial and outbuildings. A cost-effective and time-efficient way to deploy solar power is by installing solar panels on these roofs.

The mounting process is akin to that of an on-roof system, with the rails secured to the roof ridges using self-tapping screws. This setup keeps the solar panels close to the roof to reduce wind impact. The system’s waterproofing is ensured by the rubber backing on the clamps.

Standing-Seam Mounting

Standing seam roofs typically offer the lowest installed cost per watt due to the inexpensive racking systems. These systems attach to the roof seam without penetrating the roof, allowing for flush or tilted panel mounting. Higher tilts increase production but also increase costs and require spacing between rows.

Corrugated Roof Mounting

Corrugated metal roofs, often seen on farm buildings, can present installation difficulties because of the roof’s strength constraints. Extra mounting fixtures are needed to pierce and fasten the mounting system to the roof. Proper flashing and leak-proof elements are crucial to avoid water damage.

The Best Rooftop Solar Mounting Structure

How To Choose The Best Rooftop Solar Mounting Structure?

Choosing the best rooftop solar mounting structure involves understanding the specific needs of your roof and the optimal setup for maximum energy production.

Aluminium Temper and Tensile Strength

Aluminium temper refers to the process by which an aluminium alloy undergoes various treatments to achieve specific properties for different applications. These treatments can modify the metal’s strength, ductility, and hardness, among other traits.

There are primarily five main temper designations for aluminium, each marked with a suffix starting with ‘T’ to indicate a thermally treated alloy. These range from T0, indicating aluminium that has been extruded but not subjected to further heat treatment, to T6, which represents the highest level of strength achieved through a process known as “ageing.” Ageing involves heating the aluminium at specific temperatures for a set period, significantly enhancing its tensile strength.

For example, T4 tempered aluminium, while initially having medium to low tensile strength, can significantly increase in strength over time even without external heat treatment. This characteristic makes it particularly suitable for shaping and fabrication processes where surface integrity is essential. In contrast, T5 and T6 tempered aluminium offer medium to high tensile strengths, making them ideal for applications requiring robust mechanical support.

Aluminium Alloys

An aluminium alloy is basically a blend of aluminium with other elements like copper, magnesium, manganese, silicon, tin, nickel, and zinc. This blend enhances characteristics such as strength, ductility, and corrosion resistance, making the alloys suitable for a range of applications.

The specific mix of elements significantly impacts the resulting alloy’s tensile strength, with each product typically stating the alloy used in its composition. These alloys are renowned for their low density, excellent electrical and thermal conductivity, and superb resistance to corrosion in specific environments.

Mounting Structure Metal Types

Various metal finishes are on offer for aluminium mounting structures, each boasting distinct advantages. Anodised aluminium goes through an electrochemical process, enhancing its durability, decorative charm, and resistance to corrosion.

On the other hand, mill-finish aluminium, in its untreated and unpolished state, upholds more of aluminium’s inherent conductivity. Powder-coated aluminium presents a coloured finish by applying either polyester or epoxy powder, delivering an aesthetically pleasing and protective coating to the metal.

Comparing Aluminium Rail Parts

When comparing aluminium rails for mounting structures, it’s important to consider the price per metre, weight, and tensile strength. The weight per metre can indicate the amount of material used and the rail’s structural integrity.

Tensile strength, particularly in the comparison between T6 and T5 tempered rails, plays a significant role in mechanical performance, with T6 generally offering greater strength and durability.

Bracket Fixing Considerations

When evaluating the mounting structures, it’s crucial to compare the number of brackets and components per meter as well as their tensile strength. Ensuring comparable tensile strengths are taken into account is key to achieving consistent performance levels. Differences in tensile strength, especially between T5 and T6 tempered materials, may require adjustments in the quantity of components employed.

Material Compatibility and Fixing Solutions

Selecting the correct fasteners and brackets is vital to prevent installation issues and guarantee longevity. It’s crucial to consider material compatibility, especially when using various metals in fastener parts, as this could result in damage or failure. Opting for locally sourced fixing solutions typically offers greater flexibility and reliability than intricate imported fasteners.

Imported Mounting Structures

While imported PV mounting solutions may be perceived as superior, the key is to select a solar panel mounting system that aligns with local structural and climatic conditions. For instance, Europe’s heavier and denser roof substructures may not match South Africa’s typical metal roof sheeting, emphasizing the need for solutions tailored to local standards.

Rail Splicing and Bimetallic Corrosion

Rail splicing and bimetallic corrosion are additional factors to consider in mounting structures. Proper bracket spacing at splice points and the selection of compatible metals are critical to prevent undue stress and corrosion, respectively, thus ensuring the longevity and reliability of the roof installation.

Railed vs. Rail-less Mounting Structures

When deciding between railed and rail-less mounting solutions, it’s crucial to take into account the specific site needs, roof strength, and expected loads. Railed systems offer full-width support for solar panels, whereas rail-less systems demand a structurally robust roof that can manage concentrated loads. Your choice should reflect values of durability and mechanical efficiency, evaluated through professional engineering assessment.


What equipment is used to attach PV panels to a sloped rooftop?

Attaching solar (PV) panels to a sloped roof typically involves using a mounting system made up of brackets, rails, clamps, and sometimes, specialised hooks. These parts work together to securely fix the panels to the roof’s structure. The choice of equipment depends on the roof material (e.g., tiles, metal sheeting, or shingles) and the type of mounting system (railed or rail-less).

In a railed system, aluminium rails are fixed to the roof, acting as a base for the panels to be clamped onto. For tile roofs, hooks can be placed under the tiles to link the rails securely to the roof framework. Regardless of the setup, ensuring compatibility with the roof type and proper load distribution is vital for the durability and safety of the installation.

What is the difference between ground mounted and roof top solar installation?

Ground-mounted solar installation of solar panels differ from rooftop solar setups mainly in where they’re placed and the type of support they need. On the ground, these systems use either fixed standard mounts or solar trackers that adjust to follow the sun, capturing more energy.

This type suits areas with limited or unsuitable roof space due to orientation, shading, or structure issues. It’s easier to position for optimal sun exposure, potentially boosting electricity generation. Yet, they might need extra permits and take up significant space on properties.

Which solar PV mounting roof structure is not recommended for?

When choosing a roof structure for solar PV, avoid using plastic or PVC materials for support. While they may seem cost-effective and resistant to corrosion initially, they lack the durability and strength of metal-based structures like aluminium or stainless steel under various conditions like high temperatures, UV exposure, and mechanical stress.

Plastic and PVC may not offer the needed stability for anchoring PV panels securely, especially in windy or snowy areas. Therefore, experts in the field recommend against using plastic or PVC for crucial structural parts of solar PV mounting systems.

What is the difference between IBR and corrugated roofing mounting structures?

Some solar PV mounting structures on roofs aren’t advisable for those with very low load-bearing capacity or in poor condition. Solar installations, especially those using heavy-railed systems, need a sturdy roof to bear the panel weight.

Old, damaged, or lightly constructed roofs may not support the added load safely. It’s crucial to have a qualified engineer assess the structure thoroughly before proceeding. If the roof is unsuitable, options like ground-mounted systems or roof repairs and reinforcement can be considered to ensure the solar panel setup’s safety and integrity.

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