For decades, the standard roof treatment in Pakistan was bitumen — black lukh, heated and spread on the roof. Today, polyurethane (PU) coating is replacing it. Here is an honest comparison, so you can decide for your own roof.
Flexibility: The Deciding Factor
Roofs move. Heat expands them, cold contracts them, and buildings settle. PU coating is elastic — it stretches over 600% without breaking — so it moves with the roof and bridges hairline cracks. Bitumen is rigid once it cools. It cracks under the same movement, and every crack is a new leak.
Heat and Sunlight
Bitumen is black. It absorbs sunlight, heats up, softens in summer, and degrades under UV rays. White PU coating reflects up to 85% of sunlight. That keeps the coating itself cooler, protects it from UV damage, and reduces indoor temperature by 6–8°C — a benefit bitumen can never give.
Application and Repairs
Bitumen needs heating, smells strongly, and is difficult to apply evenly. PU coating is a liquid applied by brush or roller in two coats, forming a seamless membrane with no joints at all. Later repairs, if ever needed, are simple: clean the area and recoat it.
Cost: Honest Comparison
Bitumen is cheaper on day one. That is its only real advantage. But it needs reapplication far more often, and each failure brings ceiling damage, paint damage, and another round of labour cost. PU costs more upfront and lasts far longer — with Water Seal, it carries a written 5-year warranty. Over the life of the roof, PU is the cheaper option.
Verdict
Choose bitumen only if you need the lowest possible cost for a very short-term fix. For a roof you want to stop worrying about — one treatment, no yearly patching, plus cooler rooms — PU coating is the better choice.
Cost: Water Seal PU roof waterproofing starts from Rs 70 per sq. ft., with a free site inspection and an exact quote after measurement.
Frequently Asked Questions
Can PU coating be applied over old bitumen?
In most cases, yes — after proper cleaning and preparation. Loose or damaged bitumen is removed first so the PU bonds to a sound surface. We confirm this during inspection.
Is PU coating safe for water tank roofs?
Yes. The same PU system is used on water tank roofs and terraces, forming a seamless waterproof membrane.
Ask Us Which System Suits Your Roof — Free Inspection
WhatsApp: 0302 9867007 | Website: waterseal.com.pk