This is one of the most common unsolicited requests PorthouseDean receives. A solar installation company is about to install panels on an existing roof, and they want a structural engineer’s confirmation that the roof can take the additional load. Here is the answer.
The Solar Installer Is Responsible
Under the current regulatory framework, the solar installation company is responsible for confirming that the existing roof is capable of supporting the panels they are proposing to install. This forms part of their pre-installation survey and risk assessment obligations.
A competent installation company will assess:
– The rafter sizing and spacing against the panel weight
– Whether the roof structure has signs of movement or deterioration
– Whether the fixing method is appropriate for the rafter size and condition
– Whether any additional loading from wind uplift is within the roof’s capacity
For standard residential solar PV installations on well-maintained roofs with typical rafter sizes and panel weights, most existing domestic roofs can support solar panels without modification. Installation companies should follow their own technical guidance and LABC or MCS standards for this assessment.
When Does PorthouseDean Get Involved?
PorthouseDean becomes involved in two circumstances only:
1. Solar on a Roof PorthouseDean Designed
If PorthouseDean has designed the new roof structure (e.g. as part of a loft conversion or extension), and solar panels are now being added to that newly designed roof, we can confirm whether the loading is within the design. This is typically a straightforward desk exercise.
2. Commissioned Roof Loading Assessment
If a homeowner or installer wants a formal structural assessment of an existing roof for solar loading, PorthouseDean can provide this as a separately commissioned service. This involves:
– A site inspection to measure rafter sizes, spacing, and condition
– A loading assessment against the proposed panel type and layout
– A formal written report confirming adequacy (or specifying any required strengthening)
This service is subject to availability and carries a separate fee. It is not included within the standard structural design service.
What PorthouseDean Will Not Do
PorthouseDean will not provide a letter or certificate confirming existing roof adequacy for solar without first carrying out the above assessment. Signing off a roof we have not inspected or assessed is not something we are able to do responsibly.
Contact us if you require a formal roof loading assessment for solar panels.
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