Within weeks
Sagging Ridge Line — How Serious Is It?
A ridge that's no longer dead-straight is telling you something about the timber underneath. Here's what's actually going on and the timeline you should treat it on.
What you're seeing
- A visible dip or wave in the ridge of the roof, usually seen from the street
- Ridge tiles sitting unevenly
- Sometimes cracking on internal walls below the affected area
What it means
Most commonly: a ridge board that's rotted at the gable ends, or rafters that have spread because the original ceiling-joist tie has been cut (common after loft conversions). Occasionally: a structural wall plate failure.
Do this now
- Don't ignore it through a winter — accelerated wet weather makes a marginal problem a big one
- Get an internal loft inspection done
- Check whether a loft conversion ever cut original timber ties
Professional fix
Internal inspection first — usually a sister-rafter installation, ridge-board renewal, or steel-tie installation. The roof covering often stays largely intact during the repair.
Typical cost
Internal timber repairs £1,500–£4,500. Full structural correction £4,000–£9,000+.