Background
The owner of a traditional property contacted us after noticing visible sagging within the roof structure.
They wanted to understand whether the roof required major repairs or replacement.
Structural inspection
The roof space was inspected including rafters, purlins and supporting timber elements.
The extent of sagging and overall structural condition were assessed.
Findings
The roof structure had experienced long-term timber creep, a natural process where timber gradually deforms under load over many years.
This is a common characteristic of traditional roof structures.
No evidence of immediate structural instability was identified.
Recommendations
Localised strengthening measures were recommended to reduce the likelihood of future movement and improve long-term performance.
A complete roof replacement was not considered necessary.
Outcome
The homeowner received clear advice regarding the condition of the roof and avoided unnecessary replacement costs.
Outcome: Roof replacement not required. Localised strengthening sufficient. Homeowner avoided unnecessary expenditure.
Frequently Asked Questions
Why is my roof sagging?
The most common cause in traditional properties is timber creep — the gradual deformation of roof timbers under sustained load over decades. Other causes include a broken or missing purlin, spread between rafters pushing outward on the walls, or timber decay from a leak. A structural engineer can identify the cause from a roof space inspection and advise whether strengthening or replacement is needed.
Is a sagging roof dangerous?
Gentle long-term sag visible in older traditional roofs is common and rarely dangerous. However, sagging that has appeared recently, is getting worse, is accompanied by cracking in the walls below, or involves broken structural members requires prompt assessment by a structural engineer. Early intervention is almost always less costly than waiting.
Do I need to replace my roof if it is sagging?
Not necessarily. A structural survey can determine whether the sagging requires structural intervention or whether localised strengthening of purlins or rafters is sufficient. Many older roofs with visible sag are structurally sound and do not need replacement — a structural engineer's report gives you the evidence to make an informed decision.