Solar panels can sometimes be installed on a concrete garage, but the roof must be assessed first. The strength of the concrete wall panels does not prove that the roof can carry the additional weight or withstand the wind forces created by a solar array.
The roof structure, covering, fixings, condition and proposed mounting system must all be checked by a competent solar installer. A structural engineer may also be required.
Understand How the Garage Roof Is Built
Dencroft garages use reinforced concrete wall panels, but the standard roof is formed from corrugated cement-fibre sheets fitted to engineered steel angle trusses. Full details are available on the concrete garage specification page.
This distinction matters because the solar panels, mounting rails and fixings place loads on the roof structure rather than directly on the concrete walls.
An assessment should consider:
- the weight of the panels, rails and mounting system
- wind uplift and local exposure
- snow and other imposed loads
- the span and condition of the roof trusses
- the condition of the roof sheets and existing fixings
- how loads will be transferred into the main structure
- whether installation would affect an existing guarantee
An installer should not assume that a roof is suitable based solely on its age or appearance.
Can Solar Panels Be Fixed to Cement-Fibre Sheets?
Cement-fibre roof sheets can be fragile and are not designed to be walked on. A suitable mounting system must transfer loads to the supporting structure without cracking the sheets or creating leaks.
Simply drilling through the roof and sealing around the holes is not an adequate installation plan. The fixings, brackets, weather seals and supporting trusses must be compatible with the roof and solar mounting system.
If the roof is damaged or approaching the point where replacement is likely, it may make sense to complete any necessary garage roof repairs or replacement before installing solar panels. Removing an array later to repair the roof can add substantially to the work involved.
Check Older Roofs for Asbestos
Modern Dencroft cement-fibre roof sheets are non-asbestos, but some older garage roofs contain asbestos cement. The material should be identified before anyone drills, cuts, cleans or removes it.
Do not walk on, pressure wash or disturb a suspected asbestos roof. If asbestos is present, the solar installer and an appropriately trained asbestos contractor will need to determine whether the roof should be removed or replaced before the project continues.
Are Pent or Apex Roofs Better for Solar Panels?
Neither roof style is automatically better. Suitability depends on the direction and pitch of the slope, available area, shading and structural capacity.
A pent roof provides one continuous slope, which can make the layout straightforward when it faces a useful direction. An apex roof offers two slopes, although one side may receive more direct sunlight than the other.
A south-facing array often produces the greatest annual output in the UK, but east-facing and west-facing installations can still be worthwhile. They may generate more electricity earlier or later in the day, which can suit some patterns of household use.
A solar installer should provide an estimated annual generation figure based on the actual orientation, pitch and shading rather than relying on the roof style alone.
Will Planning Permission Be Required?
Solar equipment fitted to a domestic garage in England can often be installed under permitted development rights, subject to limits and conditions.
For panels on a pitched roof, the equipment should generally not project more than 200mm beyond the roof slope or extend above the highest part of the roof. Different limits apply to equipment installed on a flat roof.
Permitted development rights may not apply where the garage is within the grounds of a listed building or on a scheduled monument. Planning conditions, Article 4 Directions and local designations can also affect a project.
Rules differ across the UK, so confirm the position with the relevant local planning authority before installation.
Building Regulations and Electrical Safety
The installation must not make the roof unsafe. Its ability to carry the additional weight and withstand wind loads must therefore be assessed as part of the project.
The electrical installation must also comply with current safety requirements. This includes the panels, inverter, isolators, cabling, earthing arrangements and connection to the property’s electrical system.
An MCS-certified solar installer can design and commission the system in accordance with the relevant installation standard. Where the garage roof is unusual, has been altered or shows signs of distress, a qualified structural engineer should be consulted.
Will Solar Panels Reduce Electricity Bills?
A suitable system can reduce the amount of electricity purchased from the grid, but savings are not guaranteed. The result depends on:
- the size and performance of the array
- roof orientation, pitch and shading
- how much electricity is used while the panels are generating
- whether battery storage is included
- electricity prices and any export payments
- installation, maintenance and financing costs
Ask the solar installer for a site-specific generation estimate, expected savings and a clear explanation of the assumptions used.
Planning Solar Panels on a New Garage
If you are considering solar panels for a new concrete garage, raise the subject before the garage specification is agreed. The location, roof direction, shading and structural requirements can then be considered at an early stage.
Dencroft does not install solar panels, and final suitability must be confirmed by a competent solar installer or structural engineer. To discuss a new garage and obtain information about its proposed roof construction, contact Dencroft Garages.