A roof is leaking and water is coming into the building. What happens in the next few hours has more effect on the final cost than what the contractor does next week, because almost all of the expense of a roof leak is in the damage it causes rather than in closing the opening.
So the sequence below is deliberately ordered. Protect, record, contain, then diagnose. Nobody goes on the roof until it is dry.
First: protect people and property
Move people, stock and equipment out of the affected area, and keep them out. Water coming through a ceiling grid is a collapse risk as well as a wetting risk, because a tile holding several gallons will eventually let go and bring its neighbors with it.
Isolate electrical circuits anywhere water is near a light fitting, a distribution board or an outlet. This is the one decision worth making quickly and without debate.
Then contain. Buckets, bins, sheeting funnelled into a drain, whatever gets the water into one place and out of the building. Containing water is more useful than mopping it, because the leak is still running.
Second: record it before anybody cleans up
Photograph everything while it is wet and before anything is replaced. The ceiling, the floor, the affected stock, the grid, and the water itself.
Make a note of the timing. When did the rain start, when did water first appear, and how quickly did it build. That detail is genuinely diagnostic: a leak appearing within minutes of rain starting has a direct path through the assembly, while one appearing a day later has been soaking through insulation first.
If the cause turns out to be storm damage, this record is what an insurance claim rests on, and it cannot be reconstructed afterwards. Weather data for the date is available later; photographs of your own ceiling are not.
Third: lift the ceiling tiles
This feels wrong and is usually right. A tile holding water will fail, and when it does the water lands across a wider area along with the tile. Lifting or removing the affected tiles lets the water run into a container you control.
It also shows you where water is leaving the deck. On a low slope commercial roof the exit point is the first real clue to the search area above, because water travels along deck flutes and drops wherever there is a hole in the deck.
Fourth: do not go on the roof
A wet roof is the most dangerous surface on the building. Membrane and metal are both extremely slippery wet, standing water hides openings and soft spots, skylights disappear under reflections, and a deck that water has been working on for years may not carry a person safely.
There is also nothing to gain. No sealant, tape, patch or coating bonds to a wet surface. Anything applied during the rain is lost effort that has to be cleaned off before a genuine repair can be made, which makes the eventual job more expensive rather than less.
Clear the ground level instead. Blocked gutters, downpipes and outlets at ground level make interior flooding worse and can be dealt with safely.
What a contractor should do on arrival
In wet conditions the job is containment, not repair.
- Make safe. Fall protection, assessment of whether the roof can be accessed at all.
- Contain. A temporary cover mechanically fixed down, a diversion, or sandbagging a low spot to stop water reaching the opening.
- Book the return. The diagnostic visit happens once the roof is dry, with a date agreed before they leave.
Then, on the dry visit, the real work: tracing the entry point from the interior evidence outward, scanning for how far the wet area has spread, and producing a written finding that locates the defect on a roof plan.
Be wary of anyone who applies a permanent product in the rain and calls the job finished. The invoice should separate the emergency attendance from the repair, so you can see which one you have actually bought.
Why the repair should wait for the diagnosis
The temptation after a leak is to get something done immediately and move on. It is the most expensive instinct in building maintenance.
On a low slope roof the stain is where water left the assembly, not where it got in. Sealing the membrane above the stain puts material onto sound roofing and leaves the opening untouched, so the leak returns in the next sustained rain, often somewhere new as the water finds a different exit. Our page on how a leak is actually traced sets out the sequence that finds it.
The other reason to wait is the wet insulation. A repair that closes the opening without removing the soaked board leaves water sealed inside the assembly, where it has lost its insulating value permanently and is working on the deck and the fasteners every day. The leak stops, which looks like success, and the damage continues until the area has to be reopened at several times the cost.
After the repair
Three things are worth doing in the week after, while the event is fresh.
Get the documentation. What was found, where, what was done, photographs, and the area of insulation replaced. File it with the leak photographs from day one.
Ask what caused it. A fastener backed out, a seam opened, a flashing lifted, a drain blocked. The answer tells you whether this was an isolated defect or the first sign of a roof that is aging, and those are very different budget conversations.
Put an inspection on the calendar. Most leaks on commercial roofs are found by the ceiling rather than by anybody looking, and that is a choice rather than an inevitability.
If the building is occupied by tenants
A leak in a let building is two problems, and the second one is handled badly far more often than the first.
Tell the affected tenants what has happened, what is being done and when. A tenant who knows the leak has been contained and a contractor is booked for Thursday behaves entirely differently from one who has reported water twice and heard nothing back. The second tenant starts keeping their own record, and that record becomes a rent dispute.
Record their damage as well as yours, with their agreement, on the same day. Stock, fittings, anything of theirs the water reached. It protects you as much as them, because an undocumented claim made three months later is impossible to assess and tends to be settled on the strength of whoever sounds more certain.
The mistakes that cost the most
Four of them, in rough order of expense.
Cleaning up before photographing. Understandable, and it removes the evidence an insurance claim depends on. Thirty seconds with a phone first can change the outcome of a claim worth thousands.
Sending somebody onto a wet roof. The risk is serious and the upside is zero, because nothing bonds in the rain. This is the mistake most likely to turn a building problem into an injury.
Accepting a permanent repair applied during the event. It has not bonded, it will fail, and it has to be removed before the real repair can be made. You pay twice and wait longer.
Closing the opening without removing the wet insulation. The visible symptom stops and the damage continues underneath. This is the one that quietly turns a patch into a deck repair two years later.
Where to go next
If water is actively coming in right now, emergency leak response covers what a same day attendance should and should not include. If the leak is dealt with and the question is whether to keep repairing this roof, repair against replacement is the next page.
Common questions
What should I do first when a roof starts leaking?
Protect the inside and the people in it, then record what is happening. Move stock and equipment clear, contain the water, isolate electrics anywhere water is near a fitting, and photograph the damage before anybody starts cleaning up or replacing ceiling tiles.
- Move people, stock and equipment out of the affected area
- Contain the water with buckets, sheeting or a drain path
- Isolate electrical circuits where water is near fittings
- Photograph everything, dated, before cleaning up
- Note the time the leak started relative to the rain
The photographs matter more than owners expect. If the cause turns out to be storm damage rather than gradual wear, those images are what an insurance claim rests on, and they cannot be recreated once the tiles are replaced and the floor is dry. Note the timing too, because a leak that starts within minutes of rain behaves differently from one that appears a day later, and that difference helps locate it.
Should I go up on the roof during a leak?
No. A wet roof is the most dangerous surface on the building, visibility is poor during rain and most roof falls happen in exactly these conditions. Nothing useful can be done up there during the event that cannot be done safely afterwards.
- Wet membrane and wet metal are extremely slippery
- Standing water hides openings, soft spots and skylights
- A compromised deck may not carry weight safely
- Rain makes every repair material fail to bond
- Nothing applied to a wet surface will hold anyway
The exception is a trained crew with fall protection responding to a genuine emergency, and even then the work is containment rather than repair. No sealant, patch, tape or coating bonds to a wet surface, so anything applied during the rain is lost effort that then has to be cleaned off before a real repair. Wait for the roof to dry, and spend the time on containment inside and on clearing the ground level drainage, both of which are useful and neither of which needs a ladder.
How do I limit the damage without getting on the roof?
Work from inside and from the ground. Containing the water, protecting what it can reach and clearing the ground level drainage are all useful. If the building has safe interior access to the underside of the deck, finding where water is entering the ceiling void helps the search later.
- Contain and channel water rather than letting it spread
- Lift or remove ceiling tiles so water is visible, not pooling
- Clear ground level gutters, downpipes and outlets
- Protect electrical equipment and stock
- Mark where water appears, with the time
Lifting a ceiling tile feels counterintuitive and is usually right. Water pooling on top of a tile grid eventually brings a section down, which turns a stain into a collapse and spreads the water across a wider area. Letting it run into a bucket is less damaging, and it also shows you exactly where the water is leaving the deck, which is the first clue to where it entered.
What should a contractor do when they arrive?
Stabilize first, diagnose second. On arrival in wet conditions the job is containment: a temporary cover, a diversion, or sandbagging a low spot. The diagnostic work, tracing the entry point and scanning for wet insulation, happens once the roof is dry enough to walk.
- Containment during the event, repair afterwards
- A temporary cover is mechanically fixed, not glued down
- No permanent material is applied to a wet surface
- The return visit traces the entry point properly
- A written report locates the defect on a roof plan
Be wary of a contractor who applies a permanent product in the rain and declares the job done. It will not have bonded, the leak will return, and the material will have to be removed first. A good emergency response is explicitly temporary and is followed by a booked return visit, and the invoice should separate the two so you can see what you are paying for.
Will insurance cover a leaking roof?
It depends on the cause. Most commercial policies cover sudden damage from an identifiable event such as a storm, and exclude gradual deterioration and lack of maintenance. The distinction is decided on evidence, which is why documentation from the first day matters.
- Sudden storm damage is usually covered
- Gradual wear and deferred maintenance usually are not
- Dated photographs establish when damage occurred
- Weather records for the date support a storm claim
- Maintenance records support the claim rather than undermine it
Maintenance records help rather than hurt a claim, which surprises some owners. A roof with documented inspections and repairs is demonstrably maintained, so damage appearing after a storm is more credibly attributable to that storm. A roof with no records at all invites the opposite conclusion, whatever actually happened on the night. Check your own policy for the notice period too, because several require reporting within days and a late notification can end a valid claim on procedure alone.