Research · Paper 04 · August 2026
A fragile covering does not reduce what has to be established. It changes how. This paper sets out which coverings are treated as fragile, what can be established from above, what can only be established from below, and what cannot honestly be established at all without opening up.
A fragile covering will not reliably bear the weight of a person, including where it appears sound.
Method changes. Scope does not. The same questions still have to be answered.
Some questions cannot be answered without opening up, and the report should say so.
01 · What fragile means
A covering is treated as fragile where it will not safely support the weight of a person and any load they carry. That is a property of the material, its age, its fixings and its supporting arrangement — not of how it looks from the ground or from the air.
Asbestos cement and fibre cement sheeting; rooflights of any age, which are frequently the most fragile element of an otherwise sound roof; corroded metal decking; aged single ply and built-up felt over lightweight decks; and any covering whose fixings have reached the end of their service life. Rooflights deserve particular mention because they are often the same colour and profile as the sheet around them and are not distinguishable from above.
A recently replaced covering over an old and corroded support arrangement can be more hazardous than an old covering on sound purlins. The assessment is of the system, not the surface.
02 · What each vantage establishes
The condition of the covering: surface deterioration, cracking, displaced or missing sheets, condition of rooflights, flashings and upstands, standing water and drainage behaviour, vegetation growth, and the position and extent of anything mounted on the roof. This establishes condition. It does not establish capacity.
The structural arrangement: member type and size, spans, support centres, the fixing arrangement where visible, evidence of previous alteration or strengthening, and the load path down through the building. This establishes what the structure is. It is the only vantage from which capacity can be assessed.
The condition of concealed elements: the state of fixings where they pass through the sheet, the condition of insulation and any second covering beneath the visible one, corrosion at the sheet-to-purlin interface, and the condition of embedded or encased members. Where these govern, the honest answer is that they were not established, and the report should record that rather than infer it.
03 · The consequence
A report that does not say what was inspected, from where, and what was not accessible cannot be relied upon by a third party, because the third party cannot tell what the conclusion rests on. On fragile roofs this matters more than on any other stock, since the proportion of the building that is genuinely inaccessible is higher.
The pressure on a fragile roof is always toward assuming rather than establishing. An assumed fixing condition on a brittle sheet is precisely the assumption most likely to be wrong, and it sits directly beneath a load that generates uplift at the point where the fixings do the work.
04 · Basis and limitations
05 · Citation
Suggested citation
Raihan, S. (2026) Assessing Roofs That Cannot Be Walked On: Method, Vantage and Stated Limits. Solar Surveys Research, Paper 05. Solar Surveys Ltd. Available at: https://solarsurveys.co.uk/research/assessing-roofs-that-cannot-be-walked-on
Published under Creative Commons Attribution 4.0. Reproduce, quote and build on this with attribution. Writing about it and want something clarified, or a point expanded? Ask. We would rather it was reported correctly than quickly.
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