Timber Roof Structure Repairs

Cut roofs and our roof carpentry hub cover new-build structural carpentry — a new cut roof for an extension or a loft conversion. This page covers repairs to a roof structure that already exists: sagging rafters, rot, storm damage, or a historic roof that needs structural attention. The two are related but distinct — new construction follows a new design from the outset, while repair work starts from diagnosing what has gone wrong with a structure that is already there.

Sagging usually comes from one of a few causes: the rafters were undersized for the load they carry in the first place, water ingress has weakened the timber over years, a structural connection — a strut, collar tie, or purlin bearing — has failed or was never adequate, or added loads such as loft insulation, water tanks, or a later loft conversion have exceeded what the original structure was designed for. Diagnosing which cause applies determines the right repair.

It depends on how much of the timber is affected. Where rot is localised to one section of a rafter, we can often cut out the affected length and splice in new timber, or sister a new rafter alongside the damaged one. Where rot has spread through most of the rafter’s length, or the timber has lost too much structural section, full replacement is the safer and often cheaper option. We assess this on site before quoting either approach.

Yes. Storm damage typically shows up as displaced or cracked rafters, a ridge board pushed out of line, or straps and ties torn free where wind uplift has loaded the structure beyond what it was fixed to resist. We assess the extent of movement and damage, and repair or replace the affected structural timber to restore the roof to a sound, inspected condition.

Yes, carefully. Historic roofs often use jointing methods — mortice and tenon, pegged joints, hand-cut scarf joints — that modern carpentry rarely uses, and repairs need to respect the existing structure rather than simply bolting modern timber onto it. Where a period roof has a conservation officer or listed building consent involved, we work to whatever the consented repair specification requires.

In most cases, yes — structural repairs to a roof fall under Building Regulations Part A (structure), the same as new construction. Minor like-for-like repairs may not always need inspection, but anything involving replacing or reinforcing a structural member, or changing how load is carried, should be assessed and, where required, inspected by the local authority or an approved inspector.

For straightforward, localised repairs — a single rotten rafter end, a damaged strut — we can often specify and carry out the repair directly, using standard like-for-like sizing. For anything more extensive, where the repair changes how load moves through the roof or the cause of the damage is not simple to diagnose, we recommend a structural engineer assesses it first and provides a repair specification, which we then build to. We do not calculate structural loads independently on complex repairs.

We are not a 24-hour emergency callout service, but we respond quickly to roof structure concerns — particularly after storm damage or where a sagging rafter is causing visible movement — and can usually arrange a site visit within a few working days. Send photos and a description of what you are seeing and we will advise on urgency.