Two separate questions
Capacity and condition. Capacity is whether the structure carries the additional load. Condition is how much serviceable life the covering has left. A roof can be structurally fine and near the end of its life, or in good condition and unable to take the load. Both need answering and they are answered differently.
What an array actually does to a roof
It adds permanent weight, but that is rarely the governing issue. Wind uplift matters more: panels change how air moves across the roof and can generate significant upward force at edges and corners. Load also concentrates at fixing points rather than spreading evenly.
Older roofs and unknown structures
Most buildings have no usable structural drawings, and many have been altered. That is why an assessment surveys what is actually there rather than working from documents. Purlin sizes, rafter spacing, timber condition and the state of the fixings all matter.
If the capacity is not there
That rarely means solar is impossible. Usually it means specific members need strengthening, the array needs relocating away from a weaker zone, or the mounting system needs changing to distribute load differently. Those are design problems with design answers.
Why the timing matters
An assessment before installation is a design input. After installation it is a problem. Removing and refitting an array to strengthen a roof or replace a covering is a cost nobody budgets for.
What you get
A structural appraisal setting out what the roof carries and what it needs, and where relevant a condition report on the covering. Both in writing, which is what installers, insurers and funders ask for.
Tell us what you are building.
Send the drawings or describe the project. We confirm scope, deliverables and a realistic timescale.
Start a project