Waterproofing that actually lasts: a practical guide
Waterproofing is usually under one percent of project cost and the cause of a large share of post-handover complaints. Almost every failure traces back to preparation or application, not product.
Last updated: 2 July 2026 · 7 min read
It is a system, not a coat
A working system has a sound sloped substrate, a primer, the membrane at the specified thickness in the specified number of coats, treatment at every corner and penetration, and a protective screed or tile layer above it.
Buying a premium membrane and skipping the primer or the second coat gets you a failed system at a premium price.
Terrace specification
Slope the surface a minimum of 1 in 100 towards the outlets before anything else happens. Water that ponds will find a way through eventually.
Treat the parapet junction with a fillet and take the membrane up at least 150–300 mm on the vertical face. This junction is where most terraces leak.
Bathrooms and wet areas
Waterproof the full floor and take it up the walls to at least 300 mm, and to full height in the shower area. Seal around every pipe penetration individually.
Pond test the finished floor for 24–48 hours before tiling. It costs two days and saves breaking a finished bathroom.
What to inspect
Substrate dry, clean and free of laitance. Primer applied and touch dry. Membrane coats applied in opposite directions. Coverage matching the datasheet — measure the material consumed against the area covered. Corners and penetrations detailed before the general area.
The takeaway
Slope, prepare, prime, apply the full specified thickness, detail the corners, and pond test. That sequence is the whole job.
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