A leaking metal roof: trace the water before choosing the repair

Record whether staining appears with wind, thawing or without rain. Water can travel along underlay and structure before dripping inside. The stain is evidence, not an exact map of the opening.

If access is safe, inspect from inside the attic and protect belongings. Do not dismantle wet layers without a plan. Have a properly equipped roofer inspect outside rather than searching on a slippery roof during heavy rain.

Widespread droplets beneath cold sheet may indicate condensation. Assess indoor moisture, layer airtightness and drying potential. Sealing one lap cannot solve a problem that does not originate at a local opening.

Anti-condensation fleece temporarily retains some moisture but needs conditions to release it. It does not replace insulation or vapour control. In heated attics, assess the whole assembly, including wall and window junctions.

Assess screw seating, washer and hole condition. Both looseness and excessive compression can cause problems. Do not tighten every fastener automatically; restore the specified fixing and sealing for the substrate.

Assess the size and position of holes left by removed equipment separately. A designed repair or sheet replacement may be appropriate. A sealant plug alone may not accommodate movement or suit the coating.

Check flow direction, geometry and pitch first. A reversed lap or unsuitable detail may require partial dismantling. Tape cannot change the natural water path; restore the correct system arrangement.

Inspect chimneys, valleys, ridges and walls separately. Seal only designated locations while preserving drainage and ventilation. Thick compound spread over the surface can conceal moisture and complicate later joint repairs.

Confirm compatibility with the coating, sunlight, temperature and joint movement. An indoor product is not automatically suitable for roofing. Select material according to the repair function and system documentation.

Prepare the substrate as instructed: remove loose material and dirt and meet moisture requirements. Check primer and pressure needs. Tape width and sealant colour are secondary to adhesion and correct joint geometry.

Perforation, extensive corrosion or joint distortion can justify replacement, including incorrectly shaped flashings. Repair the substrate before fitting a new sheet; preserving a defective detail at any cost can increase future expense.

A replacement needs compatible geometry, coverage and joints. “T18” or “modular” is not enough. Establish coating and shade differences and a dismantling method that protects adjacent sheets and underlying layers.

Remove waste and document repaired areas. Watertightness checks should suit the roof design. Do not direct test water beneath laps, creating conditions unlike the rainfall the system is designed to manage.

Monitor drying of insulation and other wet layers too. Stopping the leak does not instantly dry the attic. If symptoms return, revisit the diagnosis rather than adding sealant without confirming the cause.