Most roof problems are a private matter between you, your insurer and a roofer. A few are not. If a chimney stack is leaning over a pavement, a gable end is bulging, or half a roof slope has slid towards the gutter, the risk is no longer yours alone. Neighbours, passers-by and the people who live under that roof are all exposed, and the local council has a duty to take notice. This guide explains what a dangerous structure roof looks like to a building control officer, what the council can and cannot do, and how to get ahead of the problem so that you stay in charge of the repair.
What makes a roof a dangerous structure
There is no neat checklist, because the test is about risk to people rather than about a particular defect. A building control officer asks one question: could this fall, or collapse, in a way that hurts someone or damages another property? A few tiles missing after a gale usually do not meet that bar, since the roof underneath is still carrying its load and the damage is a repair. What does meet it is a loss of structural support or a part that is about to come loose over somewhere people walk.
The faults that tend to trigger concern are these:
- A chimney stack that has cracked at the base, shifted on its flaunching (the sloping mortar collar at the top that holds the pots in place) or begun to lean.
- Ridge and hip tiles that have lost their bedding and are sitting loose, especially above a path, a drive or a neighbour's garden.
- A gable end or parapet wall (the short wall that rises above the roof edge) that is cracked, bowing or moving away from the roof.
- Rafters or purlins (the horizontal timbers that support the rafters mid-slope) that have rotted at their ends or been cut through, so the slope visibly sags or dips.
- Heavy slate or clay tiles sliding in sheets because the fixings, the battens (the thin timber strips the tiles hang from) or the nails have failed.
- Damage from a fallen tree, a vehicle strike, fire or a burst of flooding that has left the frame twisted or partly displaced.
The common thread is movement. A roof that is simply old, mossy or leaking is a maintenance problem. A roof that is changing shape, or dropping pieces, is a safety one.
Who is responsible before the council gets involved
The owner is. If you own the freehold, the roof is yours to keep safe, and that holds even if the damage came from a neighbour's tree or a storm. If you rent, the landlord normally has to deal with the structure, and a tenant who spots a roof defect should report it in writing and keep a copy. In a block of flats the freeholder or management company usually looks after the roof, though each leaseholder may pay a share through the service charge.
Councils do not want to run roof repairs. Their involvement tends to start with a report: a neighbour, a passer-by, the fire service, the police or a surveyor tells the council's building control team that something looks unsafe. An officer then visits, usually from the street, and decides whether the risk is real and immediate. Many calls end there, because the owner is contacted and agrees to put the roof right. The powers described below come into play when the risk is serious and the owner cannot be reached or does not act.
What the council can do
Councils hold powers to deal with buildings that are dangerous or neglected to the point of danger. We are roofers, not lawyers, so we will not quote section numbers, and the details vary from case to case. In outline, a council building control team may:
- Inspect the building and talk to the owner about what has to be done.
- Ask for the work to be done within a stated time, in writing.
- Close a pavement, a road lane or part of a building where something may fall.
- Carry out urgent work itself, such as propping a wall or taking down a chimney stack, when there is immediate danger and it cannot wait.
- Seek to recover the cost of that work from the owner afterwards.
That last point is why it pays to act first. Emergency work done by a council contractor aims to remove the danger quickly. It is not a repair, and it is not priced or planned with your roof in mind. A stack taken down to roof level because the owner could not be reached becomes your bill, plus the cost of rebuilding it properly later. If you can show the officer that a roofer has been called, the roof is being made safe and a date is set, you keep the choices that matter: who does the work, how it is done and what it costs.
What to do in the first hour or two
If you think your roof is dangerous, the first job is to keep people away, not to fix it. Move everyone out of rooms directly below the damaged part. Keep children and pets away from the garden or pavement beneath it. If something is hanging over a public footpath or a neighbour's property, tell the neighbour at once and, where it threatens passers-by, ring the council's building control team or, if there is immediate danger to life, the emergency services. Do not climb up to look. Our answer on whether to go on the roof to check damage explains why a view from the ground, a ladder at the eaves and a phone camera with zoom tell you most of what you need.
Photograph the damage from the ground and from upstairs windows, with the date on the file. Those pictures are useful for the council, your insurer and your roofer. Then phone a roofer and describe what you can see: the part affected, whether it is moving, whether anything is over a public place. We prioritise emergency calls, and the first visit is about making the roof safe, which can mean taking down a loose stack, securing a ridge or fitting a temporary cover. Our guide to what counts as a roof emergency helps you judge how urgent your case is, and temporary roof repairs and tarpaulins covers what a holding repair can and cannot do.
Making a dangerous roof safe, step by step
Safety work follows a fairly standard order, whatever the roof. The first step is to cordon off the area below. A roofer will often put up barriers or scaffold fans (netting and boards that catch falling material) before touching the roof. Next comes removal of anything that is about to fall: loose tiles are lifted and stacked, a cracked ridge is taken off, and a leaning chimney is dismantled course by course and lowered down in buckets or through a chute rather than dropped.
After that, the opening is made weathertight. Where a stack has gone or a slope has been stripped, a heavy-duty tarpaulin is battened down over the area, or temporary boarding and a membrane are fixed so the roof stops letting water into the structure. Wet timbers rot quickly, and plaster below will fail, so a sound temporary cover is part of making the building safe, not an optional extra. Propping comes in where a wall or timber has moved: props or braces hold the structure in place until the permanent repair is done.
Only then does the lasting repair begin. That may be as simple as rebedding and mechanically fixing a ridge. It may be rebuilding a chimney stack with new flaunching and flashings, replacing rotten rafter ends with new timber, or recovering a whole slope. Where a tree or heavy impact has distorted the frame, a structural engineer may need to say how to put it right, and we will tell you if that is the case. Our page on what to do when a tree has fallen on a roof follows this sequence for that case.
Building control and the repair itself
Repairing a dangerous roof is usually repair work, not a new roof, so the usual re-roofing thresholds apply. The Planning Portal draws the line: work touching under a quarter of the building envelope (25%) and under half of the roof (50%) generally sits outside building control applications, while anything beyond that needs approval and may bring an insulation upgrade for the whole roof. Switching to a covering that weighs 15% or more than the old one also needs approval, and the structure may need strengthening. Rebuilding a chimney stack or replacing structural timbers can be a different matter, so check with your council's building control team, or a private approver, before the work starts. If your job falls under building control, we deal with that paperwork.
If the building is listed, or stands in a conservation area, tell the council's conservation officer early. Like-for-like repairs are usually fine, but a change in material or appearance may need consent. Emergency safety work, such as taking down a dangerous stack, can still be carried out, though the rebuild may be held to the original design, so photograph everything before it comes down.
Insurance, access and neighbours
Most buildings insurance policies cover sudden damage from storms, falling trees, fire and impact, and many cover the cost of making a property safe. They rarely cover wear and tear or slow decay, which is why a sound record of what happened matters. Tell your insurer promptly, keep the photographs, and keep the receipts for emergency work. Do not wait for an assessor before making the roof safe; insurers expect you to prevent further loss, and they can usually settle emergency costs afterwards if the work was reasonable. Read your own policy and ask your insurer what it covers.
Neighbours matter more than people expect. A stack that falls into next door's conservatory is a claim against you if you knew about the problem and did nothing. Work on a party wall, or on a roof that abuts the neighbour's, may need access from their side, and talking to them early makes that smoother. A roof that overhangs a shared passage, or an alley used by others, is a further reason to put up proper barriers while the repair is arranged.
How we help
If you call us about a roof you think is dangerous, we start with a free survey, which on an urgent job means a visit to see what is moving and what can be secured. You get photographs of your own roof, and a plain explanation of what we found. We will make the roof safe first, then give you a fixed written quote for the lasting repair, and we repair where repair works, saying so if the roof has years left. We back our workmanship with a written 10-year guarantee, and the site is cleared and the waste taken away at the end. Our hub page on urgent and general roof repairs around Basingstoke lists the rest of the urgent work we take on. The number is 01256 213956, and photos of the damage are welcome on WhatsApp.
