Roofing in Kettering runs straight into the same two grades of Victorian building, and here the difference has a direct safety consequence.
The artisan housing was roofed in slate on timbers sized economically. That is fine while the covering stays as it was, and it becomes a genuine problem if somebody proposes to re-cover in concrete tile, which is substantially heavier than slate. On a roof that was marginal when built, that is not a theoretical concern. Anybody offering to re-cover an old Kettering slate roof in concrete without examining the structure first should be asked what they have checked.
On the larger houses the timbers are heavier and there is usually more margin, but the same question still gets asked rather than assumed.
Failures on both grades tend to be at the junctions rather than in the field of the roof: valleys where terraced runs meet, abutments where a rear addition joins the main roof, and chimney stacks, which on a terrace are shared, exposed on all sides and usually still carrying their original flaunching.
Re-covering triggers a Building Regulations requirement to look at insulation, and we arrange that inspection and see it through to sign off. In a conservation area the covering material is not a free choice. More on our roofing page.