The most useful waterproofing conversation happens before anyone chooses tile. Ask how the shower floor, walls, corners, and drain will connect into one system. KERDI, RedGard, and hot mop take different approaches, and the details at those connections matter as much as the product name.
What is the practical difference between the three systems?
| System | Form | Useful strength | Main control point |
|---|---|---|---|
| Schluter KERDI | Factory-made sheet membrane | Uniform thickness and integrated shower components | Seams, corners, penetrations, drain connection, and approved mortar |
| RedGard | Liquid-applied membrane | Fits irregular surfaces and can form a listed shower-pan liner | Substrate preparation, coverage, thickness, drying, and every transition |
| Hot mop | Specialist asphalt-and-felt pan | Traditional custom pan method where accepted and properly detailed | Qualified installer, pan and drain detail, ventilation, and a separate wall-waterproofing plan |
What does KERDI actually provide?
Schluter's current KERDI product page describes an 8-mil-thick sheet membrane with a modified polyethylene core and fleece on both sides. The fleece anchors into thin-set mortar, and compatible drains, bands, corners, and collars can make one connected shower assembly.
Factory thickness removes one application variable. The substrate must be suitable, the mortar must match the substrate and current Schluter instructions, and every seam, corner, penetration, niche, and drain connection still needs the specified treatment. Check the treatment around every pipe penetration too.
When does RedGard make sense?
RedGard is a ready-to-use liquid waterproofing and crack-prevention membrane. Custom Building Products lists it for interior and exterior tile applications and as an IAPMO-listed shower-pan liner. Its current product page and technical data sheet set different coverage requirements for waterproofing, crack isolation, and shower-pan use.
That distinction matters. Liquid membrane thickness is created on site, so the installer must follow the current data sheet for preparation, reinforcement, coverage, drying, and testing. Verify the specified coverage and thickness rather than judging by colour.
RedGard can be a sensible choice for a compatible, fully detailed assembly, including irregular shapes where a liquid product is convenient. It should not be treated as a cheap substitute for missing design. The selected drain, substrate, joints, and wet-area limits still have to work with the product instructions.
Where does hot mop fit in an Ontario bathroom?
Hot mop uses layers of hot asphalt and reinforcing felt to form a shower pan. It is specialist work with heat, fumes, substrate, curb, drain, and flood-test details that need to be planned as a complete assembly. It also addresses the pan, not every wet wall by itself.
Do not assume that a traditional method is automatically accepted for every project, or that a product brochure approves a mixed assembly. Ask the designer, municipality, and installer to identify the exact pan, drain, wall system, inspection sequence, and supporting documentation.
What should a homeowner ask before choosing?
Ask for the named system and current installation document. Ask which components come from that system, which approved alternatives are proposed, who owns the drain and transition details, when the assembly will be inspected or tested, and what photographs and warranty documents will be handed over. Ask to see how the proposed method matches those instructions.
What actually makes waterproofing fail?
The vulnerable places are usually changes and interruptions: drain connections, wall-to-floor transitions, corners, niches, benches, fasteners, pipe penetrations, and the boundary between wet and dry areas. Movement, poor substrate preparation, incomplete coverage, incompatible products, and rushed testing can defeat an otherwise reputable system.
The best choice is therefore the complete system that suits the shower and can be installed, checked, and documented correctly. KERDI offers uniform sheet thickness. RedGard offers liquid-applied flexibility. Hot mop remains a specialist pan option. Check the work before the tile covers it.
