Cementitious waterproofing is a cement-and-polymer slurry brushed or sprayed onto concrete and masonry to form a bonded, water-resistant layer. Rigid grades suit non-moving structures such as water tanks and basements; flexible two-component grades tolerate hairline movement in wet areas, balconies and roofs.
Rigid vs flexible
Rigid systems are single-component, cheaper and highly resistant to hydrostatic pressure, but they crack when the substrate moves.
Flexible systems add a liquid polymer component that gives crack-bridging capability, usually specified as the millimetres of crack the cured film can span.
Where liquid membranes are better
Exposed roofs with high UV load and heavy thermal cycling usually call for an acrylic or polyurethane liquid-applied membrane, often reinforced with fabric at joints and upstands.
Detailing is what fails
Failures almost never occur in the open field. They occur at penetrations, drains, wall-to-floor junctions and construction joints — all of which need fillets and reinforcing tape before the main coats.
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Reviewed by
Engr. Mahmudul Hasan
Technical Director, Terraco Bangladesh
B.Sc. Civil Engineering (BUET), Chartered Member IEB
See our technical advisory panelStandards referenced
- —EN 14891: Liquid-applied water impermeable products for use beneath ceramic tiling
- —EN 1504-2: Surface protection systems for concrete
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