A demanding detail
A roof terrace must shed water while being walked on, heated by the sun and cooled at night. The waterproofing membrane under the tiles works hard, and its weakest points are drains, upstands, thresholds and joints.
Typical failure points
Blocked or poorly connected drains, membranes that do not rise high enough behind skirting tiles, cracked tile joints, door thresholds without proper upstands and railings fixed through the waterproofing are all common sources of infiltration.
What to look for below
Staining on the ceiling below, peeling paint at the top of walls and damp that worsens after rain are classic signs. Because water can travel under the tiles before dripping through, the stain is not always directly under the defect.
