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Safely Retrofitting Roof Mounted Solar Photovoltaic (PV) Panels

You've decided how many solar panels you need, you know the size of the panels and you know how you want them to be laid out. Now you've got to work out how to get them safely up to the roof, secure them and be certain that they will stay there.

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Retrofitted Solar PV Panel System


This article describes some of the steps to take when carrying out a retrofit roof mounted solar PV installation and the typical equipment used to secure an on-roof (flat or pitched) solar PV system. We don't go into any detail about the electrical side, this article concentrates purely on the safety considerations and mechanical aspects of a typical retrofit PV installation.

Roof Assesment Survey

Asbestos Corrugated Sheeting

Assess the roof & Identify risks

This part should be carried out on first inspection and refered to throughout the system design stage. A record should be kept of what you find (ideally with pictures). Some of the key aspects relevant to roof mounting solar panels and the potential dangers, include:

  • Fragile roofing materials, including insecure, inadequate, corroded or broken roof fittings, anything that the installer or materials could potentially fall through if weight was applied.
  • Any protection at the roof edges to stop the installer, tools and or materials falling i.e something to stop a person or equipment sliding down the roof and over the edge.
  • The presence of asbestos, lead and other contaminates that could cause problems if cut, damaged or disturbed. Remember to also look at flashings, guttering, pipes and pipe insulation.
  • Insecure, inadequate, rotten or broken roof supports and rafters that may not be strong enough or big enough to handle the increased weight loading or provide a secure connection for the mounting feet.
  • Existing waterproofing and flashings, any damp, staining or corroded areas may be an indication of underlying instability.
  • External influences such as the proximity of power lines that may cause difficulties or dangers during the installation.
  • Moss, lichen or anything else that may be slippy when walked on.
Solar PV Panel Installation

Identify consequences (who and how might people be harmed)

Once you have this information think about and record the ways in which the issues that you have identified could affect the installation including:

  • The suitability of the equipment that will be installed in relation to the mounting area.
  • The suitability of the equipment that will be used for the installation.
  • The safety of the installation team.
  • The safety of others who may be using the building or be close to the building whilst the installation is taking place.
  • The long term effect of the increased weight loading on the structure.
  • Any uncovered problems that could be made worse because of the PV installation or spread to affect the installation at a later date.
Retrofit Solar PV Installation Planning

Identify suitable protections

Once you have considered these factors you are then likely to have a good idea of the best way to overcome these issues and progress, whilst reducing risks and selecting the most suitable equipment for the PV system itself and the equipment needed to carry out the installation.

Retrofit Solar PV Panel Installation

In many cases issues identified at this stage can be 'designed out' by using different equipment, changing the specification or making improvements to or changing the mounting area before the solar PV system is installed.

If there is any uncertainty, consult a building surveyor, a relevant specialist or the local building control department, this is likely to save time, money and effort later. If you are not sure, consulting a specialist and following their recomendations will give you the certainty to move forward confidently.

Scagffolding Tower

Access, Lifting & Safety Equipment

Depending on the nature of the installation and the potential risks you have identified, in conjunction with the heights you are working with, the size of solar PV system that is being installed and the stability of the roof; you may want to consider using a combination of the access, lifting and safety equipment below.

Access Equipment: General access scaffolding, tower scaffolds, stair scaffolds, trestles, ladders, roof ladders (crawling boards) could all be safely employed. You could also use Mobile Elevated Work Platforms (MEWPs) such as scissor lifts, cherry pickers and cranes.

Lifting Equipment: Gin Wheels, scaffold hoists, gantry hoists, scissor lifts, cherry pickers and cranes could all be used to safely raise the solar panels to the required height.

Commercial Flat Roof

Safety Equipment: Edge protection such as safety nets, guard rails and toe boards could be used to prevent equipment and people falling too far. Personal protection including harnesses (both to avoid a fall or reduce the consequences of a fall), could also be used but should be considered (when used in isolation) as a last resort if edge protection and other measures are not practicle.

Edge Protection for Commercial Flat Roof
The key points are to ensure that whichever installation equipment you choose it is right for the job and used correctly. Your primary aims should be to ensure that the risks involved in falling (people and materials) and the problems encountered when handling bulky and heavy solar equipment at height are reduced or ideally eliminated.

Solar Roof Mount Components (Retrofit)

There are mounting systems available to suit most types of installation and nearly all types of flat and or pitched roof. Some mounting system components common to many installation methods and the purpose of each is described below:

Solar PV Roof Mount: Foot


Mounting Feet / Roof Hooks: attach directly to the roof supports and are the main anchor points for the array. Mounting feet come in different sizes and can also incorporate extensions to raise the array depending on how far above the roof level you prefer the solar array to be (increased airflow) and the depth of the existing roof coverings (so the array rests on the rails not the roof). Mounting feet can also be used to increase the tilt of the array at an angle which is greater than the tilt of the roof if required to improve solar gain.

Solar PV Roof Mount: Extruded Rail
Extruded Rails: are secured to the mounting feet which in turn secures the rails to the roof. Extruded rails are usually made of high strenght aluminium and are used to support the weight of the solar panels and provide a stable and flat surface onto which the solar panels can be individually secured. Individual rails can be supplied in spans up to 6m.
Solar PV Roof Mount: Internal Splice
Internal Splices: are used to extend the length of the extruded rails through slotting in the insides of the two rails that are to be joined. Internal splices lock into cavities built into each rail and are secured using self tapping screws.
Solar PV Roof Mount: End Clamp

Solar Panel Clamps

End Clamps: are used to secure the outside edges of the first and last solar panel in each row of the solar array to the rails.

Centre Clamps: are used to secure the inside edges of two solar panels to the extruded rails.

Useful external resources

Other documentation that may be useful for clients and installers in relation to installating solar photovoltaics safely onto roofs can be downloaded below.

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Solar PV Installation & Commissioning

Need experienced hands and heads on-site? Our engineers and electricians are some of the best and most experienced in the business. We can add real value to any project through our flexibility, efficiency and the quality of our work.

Solar Panel Installers

Our solar PV installers, roofers and electricians have carried out installations of all shapes and sizes; building solar PV arrays onto most types of roof including commercial roofs and flat roofs. We have built ground mounted frames and installed solar panel mounting structures such as carports and canopies; we have safely installed solar panels on top of barns, in open fields, on factories, houses, workshops, stables, garages and sheds.

Solar PV Installation & Commissioning

Solar PV Mounting Systems

High quality solar panel mounting systems, quick to install and cost effective. Solutions for On-Roof, Roof Integration, Flat Roofs and Ground Mounting

Solar PV Mounting Systems

Whichever your choice of mounting system, technical or aesthetic requirements or site location, we are confident that given accurate measurements and location information we will be able to supply a structurally and mechanically sound, verified and guaranteed mounting system for pretty much any location.

Mounting systems available for quick delivery for on-roof, in-roof, flat-roof, free standing and building integrated installations. Also talk to us about custom builds including difficult or unusual projects.

Solar PV Systems & Equipment



Further reading and calculators related to designing, installing, repairing and maintaining solar photovoltaic and electrical systems:

Types of Solar Photovoltaic (PV) System

Introduction to the different types of Photovoltaic (PV) System available including Grid Tied, Off-Grid, Hybrid and Batteryless solar PV systems.

Solar PV System Components

Overview of the basic components needed to install a complete solar PV system. Introduction to solar PV panels. power inverters, AC & DC isolators and mounting systems.

Free Solar PV Calculators

A list of free solar PV calculators, solar design tools and software, Use to calculate solar yields and the Return on Investment (ROI) for solar PV systems.

Solar PV: Smart Export Guarantee

Interesting times ... The Smart Export Guarantee came into affect in January 2020. The Smart Export Guarantee is an obligation set by the government for licensed electricity suppliers to offer a tariff and to pay small-scale low carbon Generators and Micro-generators for any electricity that they export to the National Grid.

Engineering Recommendation G98

Grid Connections for Micro-Generators including Solar PV Systems and Elecricity Storage Systems in the UK. Under 16Amps Per Phase, grid synchronised.

Evaluating Solar PV Panels - Which panels to buy?

What to look for when evaluating and selecting solar PV panels for UK installations. Electrical characteristics of solar PV arrays and the safety factors used for selecting BoS equipment, also mounting options.

Solar Panels - PV Array Calculator

Solar Panels: Solar PV System sizing and power yield calculator. Use to work out roof layouts, PV array sizes, No. of panels and power yields. Based on SAP 2009.

Flat Roof Solar PV Array Spacing / Shade Calculator

The minimum required space between parallel rows to avoid shading is decided by the height of the array immediately in front, the slope of the roof and the lattitude of the installation site. This table illustrates the different row spacings required for optimum positioning in different locations.

Solar Electricity - Frequently Asked Questions (FAQs)

How to size a system?, What is kWp?, What is the difference between a kilowatt (kW) and a kilowatt hour ( kWh)?, How does a solar PV system work? Can I add more solar panels to my system? How do I know if my solar panels are working?

Preparing for a Solar Panel Installation

As with any construction project the success and efficiency of a solar PV panel installation comes down to good planning. Some advice for potential system owners preparing for a new solar panel installation.

Planning Permission for Solar Photovoltaic (PV) Systems

A solar PV installation can be classed as 'permitted development' subject to conditions and when not located within a conservation area, AONB or world heritage site.

Solar PV, Safety & The Building Regulations

Residential PV systems notifiable under Part P. Special consideration needed for Part A. A combination of serious risks for solar PV installers.

Smart Switching / Solar PV Power Switching

Available as an addition to existing solar PV systems or installed as a package alongside a new system, Smart switching puts full control of a solar PV system's power output firmly in the hands of the system owner.

Solar Photovoltaic (PV) & Electrical Glossary of Terms

An alphabetical list of many of the industry and technical terms you are likely to come across when installing a solar PV system. The glossary also defines terms that are used in roofing and electrical work as well as in solar PV installation and solar manufacturing.

Mains Power Supplies & Earthing Systems

Mains Supply and Earthing Systems: Location & accessability, supply systems, earthing, bonding, labelling, installing RCDs.

Electrical Warning Signs & Labelling

A quick overview of some common electrical warning signs and labels that you might find attached to electrical equipment.

ABB / Power One Aurora Inverter Faults and Repairs

Power One, at one point were the second ranked inverter manufacturer in the world and there are many Power One Aurora Inverters installed in the UK. The most popular models being the Uno PVI-3.0-TL-OUTD and the Uno PVI-3.6-TL-OUTD.

Fronius IG / IG Plus Inverter Faults and Repairs

Fronius IG and IG Plus series inverters have LCD displays on the front of the chassis that providing it's working, will highlight any errors with the inverter or the solar PV system that it runs.

Mastervolt Inverter Faults and Repairs

Mastervolt Sunmaster and the smaller Soladin ranges of inverters were widely installed in the UK between 2011 and 2014. Popular Sunmaster models being the Sunmaster XS2000, Sunmaster XS3200 and the Sunmaster XS4300.

SMA Sunnyboy Inverter Faults and Repairs

SMA Sunnyboy Inverters have been widely installed in the UK, some of the most popular being the SB1200, SB2000 and SB3000. High frequency models include the SB2000HF, SB2500HF, and SB3000HF. Transformerless models include the SB3000TL and the SB3600TL.

SolarEdge Inverter and Optimser Faults and Repairs

The SolarEdge system is unique and in our opinion unrivalled in terms of it's ability to monitor system performance down to panel level. This is achieved through the installation of a small unit called an optimiser.

Sonnen Macht Inverter Faults and Repairs

The problem we often find with these inverters are damaged relays, the tell tale sign of a relay failure is an Error 19: Relay or Error 19: Relay Fault warning displayed on the inverter's display.

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