Short answer
Often, yes. Photovoltaic panels add permanent load to a roof that was designed without them, and building control frequently ask for confirmation that the existing rafters, purlins or trusses can carry it. On a typical modern trussed roof in good condition the additional load is modest and a straightforward check is enough. Older roofs, long spans, slender rafters, altered or repaired structures, and in-roof systems that remove tiling all warrant closer assessment. Wind uplift on the panels and the adequacy of their fixings also need consideration.
Branded guidance note, prepared for project records and circulation to your team.
What is checked
- Additional permanent load from panels, rails and fixings
- Rafter, purlin and truss capacity in bending and deflection
- Wind uplift and the fixing of mounting rails to the structure
- Load path down to walls and, where relevant, foundations
- Condition of the existing roof timbers
Situations needing extra care
- Trussed rafter roofs that have been modified for loft storage or conversion
- Roofs with visible sagging, insect damage or historic repair
- In-roof or ballasted flat-roof systems
- Large arrays concentrated on one roof slope
How BES is typically involved
- BES reviews the panel specification and roof construction and issues a short adequacy statement or full calculations.
- Where the roof is inadequate, strengthening options are proposed.
- Reports are formatted for building control and installer records.
Typical process
- 01Confirm panel type, weight and layout
- 02Inspect or review the existing roof structure
- 03Load assessment and member checks
- 04Issue of adequacy statement or calculations
- 05Strengthening design if required
Common misconceptions
Commonly assumed
“Panels are light, so no check is needed.”
In practice
The added load is small but permanent, and some roofs have little reserve capacity — particularly modified trussed roofs.
Commonly assumed
“The installer's paperwork covers structural adequacy.”
In practice
Installer documentation covers the array; the existing roof structure is a separate engineering question.
Related tools and services
Resource Centre tool
Beam Deflection Check
Estimate the elastic deflection of a simply supported beam under a uniformly distributed load and compare it with a selected span-based deflection limit.
Open Deflection Tool →Resource Centre tool
Structural Project Navigator
Answer a few straightforward questions to identify the likely structural engineering input, information requirements and next steps for your project.
Start Project Navigator →Related questions
Discuss your project
General guidance only goes so far. Describe your building and what you are planning, and you will receive project-specific advice from a Chartered Structural Engineer.
Discuss Your Project →Next scheduled review August 2027
Disclaimer
Indicative result only. The calculation depends on the assumptions and information entered and does not constitute structural design or professional advice. Do not use the result for construction, procurement, Building Regulations submissions or safety-critical decisions. All results must be independently verified by a suitably qualified structural engineer before being used for design, construction or regulatory purposes. Bebbington Engineering Studio Ltd accepts no responsibility for reliance placed on unverified results.