Maintenance and repair
What should you do after spotting a roof leak?
In brief
After noticing a roof leak, first limit damage inside the building and ensure safety rather than immediately searching for the source above the stain. Water can travel along roof components, so the wet patch need not lie beneath the leak. Check whether the problem occurs during ordinary rain, strong wind or a thaw, and whether the stain grows gradually or appears suddenly. Recording these conditions helps choose places to inspect without unnecessary dismantling. Leave the diagnosis of causes and the scope of repair to a contractor, who should describe the defect found.
What to do first?
Move objects away from the wet area and collect the water if this can be done safely. Do not stand beneath a clearly bulging ceiling. If water reaches the electrical installation, do not touch wet appliances or fittings. The method of disconnecting the affected circuit and further actions should be safe for the people in the building.
Do not go onto a wet roof during rain. Slippery sheet metal and strong wind can be a greater hazard than the leak itself. Have the roof slope temporarily covered by a team with suitable access and safeguards. A temporary cover is intended to direct water away from the building, not to collect it above the damaged area.
How to gather information for the roofer?
Take photographs of the water stain, the wet elements in the attic and the visible section of the roof slope. Note whether the problem occurred during ordinary rain, strong wind or a thaw. It is also important whether the stain grows gradually or appears suddenly. Such a description helps to select the places to be checked without unnecessary dismantling. Record the time the stain appeared and the wind direction during the rainfall. This can help to reconstruct the conditions of the leak.
If you have roof documentation, prepare the drawings, the covering instructions and photographs from installation. Information about recent work on the chimney, antenna or installation on the roof slope can also be useful. Do not immediately assume the last team is at fault. A change in conditions may merely have revealed an earlier leak.
Why is the source sometimes far from the patch?
Water can run down the membrane, the rafter or the underside of the sheet. It only emerges at a joint, an opening or a lower point in the layer. A repair carried out directly above the stain may therefore be ineffective. The inspection should also cover the higher section of the roof slope and adjacent roof penetrations.
Pay attention to the chimney, the roof valley, the roof window and the ridge. They are not inherently defective, but they contain more joints than a simple sheet surface. Wind can force water under an incorrectly laid overlap. During a thaw, on the other hand, drainage may be blocked by ice lying in the eaves area.
Is it definitely a leak from outside?
Drops under the steel sheet may come from condensation of water vapour. Warm, humid air from inside reaches the cool surface and releases moisture. Symptoms may intensify with temperature changes, even without rainfall. Sealing the joints on the outside will not then solve the cause of the problem.
The airtightness of the layers on the room side and the operation of the designed roof ventilation must be checked. The mere presence of a membrane does not provide the answer. Its joints, service penetrations and the arrangement of the entire assembly are important. In cases of complex dampness, an assessment by a person dealing with building physics may be needed.
When is a local repair sufficient?
If the leak concerns a single damaged fastener or a correctly designed flashing, a repair limited to that spot is possible. First, however, the substrate must be assessed. A screw will not hold properly in decayed wood, and a new seal will not compensate for a deformed sheet.
In the case of an incorrectly shaped flashing, too small an overlap or extensive corrosion, replacement of part of the covering may be needed. It is not worth hiding such a spot under a thick layer of sealant. This will make later repair more difficult and may trap water. Sealants are selected according to the coating and the expected behaviour of the joint.
What should be done with wet layers?
After the water supply has been removed, the insulation, timber and interior finish must be assessed. Their drying out may require part of the assembly to be exposed. Closing a wet layer with a sealed covering will not speed up the repair. It must also be established which elements have retained their properties and can remain in the roof.
Do not assess the degree of dampness solely by touching the accessible surface. Moisture may persist deeper or in the adjacent space. The drying method should take the roof construction into account. In the case of major flooding, a plan for the sequence of works is needed so that further wet spots are not covered up.
How can you confirm that the problem has been resolved?
The contractor should describe the cause found and the scope of the repair. Keep photographs before the detail is covered. Carry out checks also during the next rainfall with a similar pattern. The absence of water after a short, gentle rain does not always confirm the tightness of a spot that only leaked in strong wind.
If the stain grows again, return to the diagnosis instead of applying another layer of sealant. Two independent causes are possible, or moisture left in the assembly. A reliable record of the repair allows a recurrence of the leak to be distinguished from slow drying of the materials and the next step to be planned.
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