The four families
Polyurethane (PU) liquid membrane
Elastic, seamless, bridges hairline cracks, stays flexible in Malaysian heat. The default for exposed flat RC roofs, car porches and balconies. RM9–15 per sq ft installed; 8–12 years. Needs a dry, primed slab and the specified thickness — two thin coats is the classic failure.
Acrylic elastomeric coating
Water-based, cheaper, reflective (cooler roof), easy to re-coat. Good over metal and tiled roofs and on light-duty slabs with no ponding. RM6–10 per sq ft; 5–8 years. Not for slabs where water sits — acrylic softens under standing water.
Bitumen — torch-on membrane or liquid
Sheet membrane heat-welded to the slab. Robust, takes foot traffic, long-lived, the choice for larger flat roofs and under tiling or screed. RM10–18 per sq ft; 10–15 years. Needs a skilled crew and a gas torch; not a DIY product.
Cementitious / crystalline
Cement-based, bonds into the concrete, works from the negative side (below) as well as above. Bathrooms, water tanks, basement walls, and slabs that will be tiled over. RM8–14 per sq ft; 10+ years. Rigid — not for slabs that move or crack.
Why coatings fail
- Coating over a failed membrane. The old layer lets go and takes the new one with it.
- Damp slab. Moisture underneath blisters the coating in the first hot week.
- Thickness. Every system has a specified wet-film thickness. Skimping is invisible on day one.
- Corners and up-stands. No reinforcement fabric at edges, parapets and pipes. Most leaks in a "waterproofed" roof are at a corner.
- Ponding. Water that can't reach the drain sits and finds a way. Fix the fall first.
Brands
Sika, Mapei, Bostik, Fosroc and Nippon Paint all sell systems with Malaysian technical support and honoured warranties. Ask for the product name and data sheet on your quote; "waterproofing, 2 coats" isn't a specification. Our waterproofing service sets out how we prepare and apply.