Mounting solar panels on the roof

Table of contents

Domestic photovoltaic systems are most often installed on the roofs of houses. Such a solution saves space on the plot, but is also associated with a lower installation cost than ground-mounted systems.

The system for mounting solar panels on the roof is a key element of a successful photovoltaic installation. It requires precise workmanship, and the right design solutions allow the safety and strength of the entire structure to be maintained.


1. Solar panel mounting system – challenges

All elements of fixing solarc panels on roofs are exposed to the adverse effects of intense weather conditions. Therefore, they must be resistant to mechanical loads caused, for example, by strong wind or rainfall, but also by impacts from hail and even small stones. The installation must also face any chemical hazards in the environment, such as salt spray or acid rain. In view of this, mounts must be made of corrosion- and UV-resistant materials. The main task of the mounting system is to hold the solar panels in a stable position, preventing the panels from being damaged or knocked off the roof by strong winds.

Photovoltaic systems can be installed on almost any roofing, and only the complexity of the installation remains variable. Different roof coverings require different mounting systems. Installation is different on a tile roof, different on a tiled roof, and different on a flat roof.

Each installation of elements directly to the roof sheathing is followed by the installation of adapters and aluminum rails, to which we screw the solar panels. The leveling of the rails cannot be omitted, so that the installation will look aesthetically pleasing on the roof. The PV panel is attached to the rack with clamps.


2. Mounting systems for solar panels

2.1. Solar panels mounts dedicated to sloping roofs

2.1.1 Sheet metal roofing

The most common roof covering in Poland is tinplate. Attaching solar panels to sheet metal tiles can be done in two ways. In the first, we start by drilling holes and screwing in double-threaded screws. The double-threaded screws contain a gasket that protects the roof from leaks. It is good practice to use silicone in places where the gasket is not able to protect the roof surface well. Such silicone does not chemically react with the gasket and is weatherproof.

mocowanie paneli fotowoltaicznych na dachu z użyciem śrub dwugwintowych
śruba dwugwintowa

Way number 2: fixing photovoltaic modules on a tile roof – mounting the system with a bridge.

montaż na dachu
mocowanie paneli fotowoltaicznych na dachu z użyciem mostka


2.1.2 Sheet metal on the seam

The installation of a photovoltaic system on seamed sheet metal roofing is quite easy. Directly on the seam (which can be flat or round in shape) clamps are attached with screws. Then the rail is attached to the clamp, using a hammer-head screw and a contour fastener.

With this method of installation, it is not necessary to drill through the roof sheathing – it is a non-invasive system, so there is no danger of leaks.

montaż na dachu blacha na rąbek
Mocowanie paneli fotowoltaicznych blacha na rąbek


2.1.3 Trapezoidal sheet

Trapezoidal sheet from the point of view of solar panels brings many advantages. First of all, thanks to its construction, which allows air circulation under the panels, but also the indentations allow rainwater to run off without causing water to pile up on the roof surface.

Installation of mounts photovoltaic modules to trapezoidal metal sheets is always done to the convex part of the roof. We distinguish between two methods of attachment. The first method is to directly mount the adjustable bracket to the sheet metal with special screws. The other way is to install special bridges, which will be fixed with screws.

montaż na dachu z blachy trapezowej
mocowanie paneli fotowoltaicznych uchwyt regulowany
montaż z użyciem mostka trapezowego


2.1.4 Ceramic tile

Installation of the system on ceramic tile roofing requires moving or completely removing individual tiles. In this place we fix tile brackets, which are mounted to the rafters. Then the missing tiles should be filed so that they tightly overlap the protruding bracket.

montaż paneli fotowoltaicznych na dachu dachówka ceramiczna
Mocowanie paneli fotowoltaicznych dachówka ceramiczna


2.1.5 Carpeting

Installation on plain tile sheathing is carried out in a similar way as with clay tile. At the installation sites, the tile must be removed and in this place the brackets must be fixed, which must be screwed to the rafters. Installation of the removed tiles must be done with care so that they adhere evenly.


Mocowanie paneli fotowoltaicznych na dachu karpiówka
montaż na dachu z karpiówki


2.1.6Bituminous tile

With asphalt roofing tile (asphalt shingles) the basis of the mounting system for photovoltaic modules are mounting brackets, which are installed after removing the sheathing to the boarding or (without removal) directly through the sheathing. Differences in mounting methods depend on the manufacturer of the mounting.

montaż z użyciem uchwytu typu l

2.2. photovoltaic panel mounting systems dedicated to flat roofs

Mounting solar panels on flat roofs requires a special design to position the modules at the right angle. The optimal angle of inclination, i.e. one that results in satisfactory electricity production, is about 30-40 degrees. Such siting of modules makes them more susceptible to weather conditions, especially strong wind, which has the space to lift the installation from the roof. Proper installation with the use of high-quality mounting systems for photovoltaic modules will help protect installations from such a threat.


2.2.1 Mounted to the roof structure (intrusive)

The rack on which PV panels are mounted is in the shape of a right triangle. The lower frame of the triangle, which stands directly on the roof, is mounted to the roof surface with screws, bolts or pins. Such a solution makes it possible to choose any optimal angle of inclination of PV panels, and thus increase the efficiency of the installation. Great care is required to seal the places where the roof structure has been disturbed.

Such a mounting structure favors the installation of bifacial, or birefringent, panels, one surface of which absorbs direct radiation and the rear surface absorbs reflected radiation. By using bifacial panels, we can increase the annual electricity gain by up to 30%! With bifacial panels, a rear obscuration is not installed to protect the panels from uplift winds.

Mocowanie paneli fotowoltaicznych na dachu inwazyjne
Mocowanie paneli fotowoltaicznych na dachu k-17

Installation with longitudinal and transverse rails applied to roofs covered with sandwich panels.

mocowanie paneli fotowoltaicznych na dachu z użyciem szyn wydłużnych
mocowanie paneli fotowoltaicznych na dachu z użyciem szyn poprzecznych


2.2.2. Ballasted-ballasted (non-invasive) systems

Ballasted systems have two significant advantages. First, they are easier to install. Second, they reduce the risk of damage to the roof surface. The limitation in the installation of such a structure is the load capacity of the roof, as such structures require an average load strength of 56kg per PV module of 1.65 x 0.99m. The sheer weight of the load depends on a number of factors, such as windiness, the height of the building and the angle of inclination of the modules. In addition, the coefficient of friction between the roofing and the mounting system is important.

Mocowanie paneli fotowoltaicznych na dachu układ wschód zachód
Mocowanie paneli fotowoltaicznych na dachu układ na południe

Mounting of photovoltaic panels – ballast structure mounted on triangles.

dociążenie mocowań


2.2.3 Self-supporting systems for mounting solar panels on the roof (non-invasive)

Welded systems are mounted to the roof membrane on fixing plates, which are designed to distribute the load over the footprint. The main advantage of this solution is the welded mounting, which ensures the transfer of forces that lift the structure. This type of assembly does not require the use of ballast or the execution of roofing penetrations. The welded structure with roofing felt/membrane mounting plates makes it possible to achieve an angle between 15 and 35 degrees. Below photos – installation of photovoltaic modules on paper:

montaż paneli fotowoltaicznych na papie
Mocowanie paneli fotowoltaicznych na papie


Instructions for installation of mounting structure on roofs with roofing type “plain” for photovoltaic modules. BELOS-PLP
B. Szymanski Fotovoltaic Installations, Issue VII, GLOBEnergia


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