4 Reasons Bali Roofs Leak – And How to Fix Each One | BaliWaterproof

1. Drainage Outlet Failure

Where the roof membrane terminates around a drain pipe, movement from daily thermal cycling creates micro-cracks. Even a 1mm gap at this junction is enough to let significant water ingress during heavy rain. You'll typically notice water appearing around a specific point in the ceiling below — not a diffuse damp area, but a defined drip location. Fix: re-seal or replace the drain flange with proper membrane integration.

2. Parapet Wall Junction Failure

Where the flat roof membrane meets the parapet wall. If the membrane wasn't turned up the wall face behind the capping tile, water drives under the cap and runs down the wall face behind the membrane. The repair requires either re-doing the membrane turn-up or installing a metal capping flashing over the parapet.

3. Membrane Delamination

The membrane lifts off the concrete substrate — usually because it was applied over a weak surface laitance layer that has since separated from the concrete below. You might see bubbles or areas where the membrane sounds hollow when tapped. Water pools under the delaminated areas and eventually finds its way through. Fix: remove the delaminated membrane, treat the substrate, and apply a new system correctly bonded to clean concrete.

4. Structural Crack Water Ingress

Movement cracks through the concrete slab — either settlement cracks or thermal expansion cracks — allow direct water ingress where no membrane bridges them. Flexible membranes with good crack-bridging capability (polyurethane liquid membranes) handle cracks up to about 2mm. Wider structural cracks need crack injection treatment before new membrane application.