Waterproofing materials for roofs and floors
Polyurethane and acrylic waterproofing membranes and coatings are widely used for flat roofs, rooftop terraces and bathrooms, forming a seamless membrane that prevents water from penetrating the concrete structure.
Leaks are the leading cause of premature building deterioration. Water seeping through a roof slab not only stains ceilings and peels paint but also corrodes the reinforcing steel, shortening the life of the structure. Choosing the right waterproofing system for each area saves on repair costs later.
Common liquid-applied waterproofing systems
| Material system | Elongation | UV resistance | Suitable areas |
|---|---|---|---|
| One-component polyurethane | Above 400% | Requires a protective topcoat or aliphatic grade | Flat roofs, rooftop terraces, balconies |
| Water-based acrylic | Approx. 200 – 300% | Good | Exposed roofs, exterior walls |
| Two-component polymer-modified cement | Low to medium | Good | Bathrooms, water tanks, basements |
| Hot-spray polyurea | Above 300% | Requires a protective topcoat | Large roofs, abrasion-prone floors |
Waterproofing flat roofs and rooftop terraces
Flat roofs are exposed to direct sun, with surface temperatures that can exceed 70 °C, plus heavy rain and ponding water. Highly elastic PU membranes bridge hairline cracks in the concrete without tearing. In areas with foot traffic, apply an additional protective layer or tile over the membrane once it has dried.
Waterproofing bathrooms
Bathrooms have many pipe penetrations through the floor, and wall-floor corners are weak points prone to leaks. Polymer-modified cement or PU membranes are applied up the base of the walls by about 20 to 30 cm, with reinforcing mesh at corners and pipe penetrations.
Basic application steps
- Clean the surface, removing dust, oil and weak mortar.
- Treat cracks, pipe penetrations and corners with a specialized sealant.
- Apply a primer to improve adhesion and seal pores.
- Apply at least two coats of membrane, each perpendicular to the previous one.
- Conduct a flood test for at least 24 hours before finishing.
Common mistakes
Common mistakes include applying over damp concrete, applying the membrane thinner than specified and skipping detail treatment. Actual coverage is typically about 1.2 to 1.5 kg/m² for two coats of PU.
For roofs that already leak and have an old waterproofing layer, assess the adhesion of the old layer before recoating. Blistered or peeling old layers must be completely scraped off; otherwise, the new layer will peel along with it after just one rainy season, no matter how good the material.
Contact AMS Vietnam for advice on the right waterproofing system for the roofs, floors and bathrooms of your project.
