Which system, and why not the other one

Both are modified bitumen sheets applied by torch. APP is modified with atactic polypropylene, giving a high softening point and good heat and UV tolerance.

Coba is a thick cementitious build-up that creates the fall, insulates the slab and forms the barrier all at once. A membrane is a thin sheet that does only the barrier.

Polyurea is spray-applied with heated plural-component equipment and gels in seconds, giving a seamless high-build film that can be walked on within the hour. Polyurethane coatings are applied conventionally, cure over hours to days, and cost far less to mobilise.

The deciding question is whether the crack is moving and whether it is wet. Polyurethane reacts with water, expands and stays flexible — it stops active leaks.

Both are pre-applied below-grade systems. HDPE bonds mechanically to concrete cast against it, so water cannot track behind it.

Cementitious coatings are rigid, breathable and bond well to damp concrete — which is why they suit tanks and internal tanking. Liquid membranes are flexible and bridge movement, which is why they suit terraces and podiums.

Both are protective finishes laid over a completed terrace waterproofing layer — neither is a barrier in itself. China mosaic is reflective and reduces heat gain; Shahabad is a dense natural stone giving a flatter, more walkable surface.

Positive-side waterproofing sits on the face the water arrives from, so water pressure pushes it against the structure. Negative-side sits on the dry face, so pressure pushes it off.

Crystalline systems penetrate concrete and grow crystals inside its capillaries, becoming part of the concrete. Surface coatings sit on top.

Tiling a terrace is not waterproofing it. Tiles are a wearing and protective surface; the joints between them are permeable and the bedding mortar is not a barrier.

Damp proofing resists moisture vapour and capillary rise. Waterproofing resists liquid water under pressure.

TPO seams are hot-air welded into a homogeneous joint as strong as the sheet, and its reflective white surface reduces roof heat gain. APP is torch-applied bitumen, cheaper and more forgiving on detailed areas.

Repair extends a building's life; redevelopment replaces it. The decision should follow a structural audit, not sentiment or a contractor's quotation.

Both restore or add structural capacity. Carbon wrapping bonds high-strength fibre to the existing member, adding almost no weight or size.

Both are exterior coatings over prepared render. Elastomeric is applied at higher film build and stretches to bridge hairline cracks; acrylic is thinner, cheaper and has good colour retention but limited crack bridging.

Membranes and coatings need a dry, prepared substrate and full cure time, so they belong before the rains. Injection grouting works with water present because the resin reacts with it.

Box type wraps the entire below-grade structure in one continuous barrier — under the raft, up every wall, sealed at the top. Conventional remedial treatment addresses the leaks you can find from inside.

A food-grade lining carries current certification for contact with drinking water. A standard waterproofing coating does not, regardless of how well it performs technically.

Injection delivers material into the full depth of a crack under pressure. Surface filling covers the visible line.

Both are horizontal decks, but a podium carries soil, vehicles and services above occupied space, and its barrier is buried under all of it. That makes podium work less forgiving: the detailing is denser, the protection is mandatory, and the barrier is unreachable afterwards..

On a historic lime-mortar building these are not interchangeable. Lime is soft, breathable and allows the wall to dry outward.

An admixture reduces the permeability of the concrete itself. A membrane is a barrier applied to it.

Spray systems are seamless and follow complex geometry without laps. Sheet systems have consistent factory-controlled thickness but need every lap sealed correctly on site.

A painting contractor makes a facade look finished. A waterproofing contractor establishes why it is wet first.

Over-the-counter sealants and tapes have a genuine role in stopping a specific small leak temporarily. They have no role in treating a terrace, a basement or a wet area, because none of them address falls, junctions, penetrations or the substrate..

On a terrace the practical difference is laps versus thickness control. Sheet membrane arrives at a guaranteed thickness and depends on the torch operator sealing every lap.

Structural repair cuts back behind the reinforcement, treats the steel and rebuilds the section. Cosmetic patching fills the visible hole.

Proper bathroom waterproofing opens the sunk, treats the slab, collars every penetration and tests before filling. Surface treatments applied over existing tiling cannot reach the penetrations, which is where almost all bathroom leaks actually originate..

Reactive work fixes leaks after they appear; preventive work installs a system before they do. Reactive is cheaper per intervention and more expensive over a decade, because each leak has already wet the structure by the time it becomes visible..

Coatings treat area; grouting treats a path. Diffuse seepage across a wide surface wants a coating.