Membrane, PU or coating — which do you need?
“Just waterproof it” sounds simple, but the wrong method on the wrong surface is why so many repairs fail. Here’s how the three main systems differ.
Waterproofing · A 5-minute read
Waterproofing isn’t one product — it’s a family of systems, each suited to a different surface, movement and level of exposure. Matching the method to the problem is the whole game.
Torch-on membrane
A heavy bituminous sheet is heat-bonded to the surface, forming a thick, continuous barrier. It excels on flat concrete roofs, large decks and gutters that take standing water and full sun. Because it’s robust, it’s the go-to for areas that need to shrug off heat, foot traffic and monsoon rain for years.
Best for: flat roofs, exposed concrete decks, gutters.
PU (polyurethane) injection
When water is actively seeping through a crack — in a basement wall, a slab or a retaining structure — PU resin is injected under pressure into the crack. It reacts with moisture, expands and seals the void from the inside. It’s ideal for stopping live leaks without demolishing the surrounding surface.
Best for: cracked walls, basements, slabs with active leaks.
Acrylic & cementitious coatings
Liquid-applied coatings are brushed or rolled on to form a flexible film. They’re perfect for wet areas — bathroom and kitchen floors before tiling, balconies, planter boxes and small roofs. They accommodate slight movement and are easy to detail around drains and upturns.
Best for: bathrooms, balconies, planters, small roofs.
How we choose
We look at three things: the substrate, how much it moves, and how much water and sun it faces. A balcony that flexes in the heat needs a flexible coating; a leaking basement crack needs injection; a baking flat roof needs membrane. Sometimes a job uses two systems together.
Not sure where to start?
Send us a photo of the damp area and roughly where it sits in the building. We’ll tell you which system fits and quote it as a fixed price — no guesswork, no upsell.