The watertight membrane: application, sealing, transitions and WC cisterns

Under BBV, the watertight membrane beneath the tile is applied and sealed as a single, continuous system — because a membrane is only waterproof if it has no unsealed gaps.

Applied as a complete kit

The membrane is installed using the components included in the watertight covering kit (6.1), applied per the system's method (6.2), and sealed at every vulnerable point (6.3). Nothing is mixed in from outside the kit; the system works because its parts are tested together.

Transitions — where systems meet

Real rooms often need more than one system, so BBV is specific about junctions:

• Transitions between different covering kits (6.4) are detailed so the two membranes join without a gap.
• Transitions to a membrane intended for another surface material (6.5) — for example where tiling meets a painted or sheet-covered area — are sealed so the barrier stays continuous across the change.

The built-in WC cistern

A WC with a built-in flush cistern (6.6) is a classic weak point, and BBV gives it dedicated membrane detailing so the concealed cistern's penetration through the wall is properly sealed. Installation instructions (7) govern the whole process.

Why continuity is everything

Water finds the one place the membrane isn't sealed. The entire point of these rules is that there is no such place — every application, junction, transition and awkward fitting is closed. That continuity is what turns a set of components into a genuinely watertight room.

What M5 brings to Dubai

We apply the membrane as one approved kit, seal every junction and transition, and give the built-in cistern the detailing it needs. It's invisible behind your tiles — and it's the difference between watertight and merely tiled.

Official source: this is M5's plain-language summary, not the official text. For the full rules see Byggkeramikrådet (BKR) — bkr.se.