Solar panels: Can your roof handle the weight?

In this article, we take a closer look at how to ensure your roof is strong enough for the installation, while avoiding overly technical jargon.‍

How do we assess the load-bearing capacity of the roof?‍

All solar systems installed by us in Sunday Power, are carefully designed and projected by engineers. They perform calculations based on both local wind and snow loads, in line with strict European and Norwegian standards. The requirements ensure that the weight of the photovoltaic system is carefully matched to the capacity of the roof.

“Our installers work closely with assembly system suppliers to create a detailed ballast and weight plan for each project. This gives us a quality assurance (QA) that guarantees that all conditions affecting weight are considered before installation,” says Kjetil Laupsa Steine, head of deployment at Sunday Power.

Read also: Solar cells and insurance — not difficult, but important

The total load determines

On flat roofs, we lay ballast stones on the rack under the panels to ensure stability against wind and snow. Each ballast analysis is carefully documented to ensure that all requirements and regulations are followed.

We also collect information about the load-bearing capacity of the roof in cooperation with the owner of the building.

A solar system typically weighs around 20 kg/m², which is relatively small. However, it is the overall load, including snow, that can affect the roof's ability to bear its weight.

According to the Consultative Engineers for Construction (RIB) in Ramboll, it should be safe to install solar photovoltaic systems without special snow-shoveling procedures on buildings built after 2003. For older buildings, you may want to plan walkways between the panels to be able to remove snow if necessary.

Example from Eastern Norway

‍In most cases, the solar panels make up a very small portion of the total weight the roof is sized to withstand.

“Right now we have a project in Eastern Norway where the roof is dimensioned for a snow load of 4.5 kN/m², which corresponds to about 450 kg/m². The solar system we install will weigh around 15-20 kg/m², which is negligible compared to the capacity of the roof. But projects are of course assessed individually to ensure that the roof can withstand the weight, assures Kjetil in Sunday Power.

What about older buildings?

• Buildings from before 1980: These buildings were designed keeping in mind that roofs had to be shoveled for snow every 5 years. The roof structure is therefore dimensioned for lower snow loads, and it can be challenging to remove snow without damaging the panels. Snow melting facilities may be needed to handle large amounts of snow.
• Builds from 1980—2003: Roofs during this period were made taking into account snow shoveling every 15-20 years. Solar panels can usually be installed, but it is important to consider the possibilities of snow shoveling together with operational personnel.
• Build after 2003: Modern buildings are designed to withstand snow loads, which makes them well equipped for photovoltaic installations. There is rarely a need for special measures for snow shoveling.

In all cases, at Sunday Power we ensure that the installation is adapted to the specifications of the building, so that the photovoltaic system becomes a safe and efficient solution for your roof.

Read also: Solar cells in winter — should I worry about snow on the roof?
‍