Plenty of old Norfolk roofs have a gentle wave in them and always have. Timber settles, walls move slightly, and a two-hundred-year-old cottage that has held its shape for a century is not usually an emergency. What matters is whether the movement is historic and stable or active and getting worse.
Historic or active?
The useful evidence is change over time. Old photographs, a dip that neighbours remember being there twenty years ago, and plaster cracks that have been decorated over and not reopened all suggest settled movement. Fresh cracking, gaps opening at the wall head, doors that have started to bind, and tiles that have begun slipping in the middle of a slope suggest something is moving now.
What is usually behind it
In roofs of traditional construction the causes are fairly limited and generally identifiable from inside the roof space.
- Rafters spreading at the feet, pushing the wall plates outwards
- A purlin that has deflected or lost its bearing into a gable wall
- Ceiling ties cut or removed during a past loft conversion
- Rot at rafter feet where gutters overflowed for years
- Overloading, often from a heavier covering than the roof was built for
The covering can hide it or reveal it
Replacing a slate roof with concrete tiles adds significant weight, and we still see roofs where a covering swap decades ago is the reason for today's deflection. Equally, stripping a roof is the point at which the true condition of the timbers becomes visible, so structural work and a re-roof frequently go together.
Where our work stops
We are roofers. We can replace rotten rafter feet, sister timbers, renew battens and rebuild the covering to spread load correctly. Where the movement is structural, spreading walls, a failing purlin bearing, or anything involving load paths, the right step is a structural engineer's assessment first, and we will tell you that rather than take on work that needs someone else's design.
Common questions
Is a dipped ridge dangerous?
Not usually in itself. Historic, stable settlement on an old roof is very common. Movement that is progressing needs assessing, and that assessment is worth having before spending money on a new covering.
Can a new roof straighten the line?
Partially. On a re-roof the battens can be packed to take out some of the visual dip, but the underlying structure still governs. Pretending a covering can correct a structural problem is how people end up paying twice.
Do you work with structural engineers?
Yes. Where a report is needed we will explain what to ask for, and we price and carry out the roofing works once the structural approach is agreed.
My roof was re-covered in concrete tiles. Should I worry?
It is worth having the timbers looked at. Concrete is substantially heavier than the slate it often replaced, and older roofs were not always designed for it.