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What the H1 classification provides
H1 identifies reduced water absorption in the board. The manufacturer specifies boards from this family for interior systems in moderately humid environments. This does not make the finished wall waterproof or mean that every green product is equivalent. The chosen solution should identify the commercial product and its technical data sheet, rather than relying on a visual description.
A bathroom has different exposure zones
A ceiling, a wall away from the shower and a surface receiving direct water involve different conditions. We ask about room use, ventilation and contact with water when assessing the project. Splash zones and direct water exposure require compatible protection and finishes to be defined. Replacing one board with another does not settle those decisions or describe the entire construction.
Junctions must be resolved as well
Pipe penetrations, corners, the bottom of the wall and junctions with baths or shower trays need attention during design. Tiling should be coordinated with the support and the selected protection system. Clarify who will carry out each part so that preparation and finishing details form a coherent scope. Access for services should also be planned where it is needed.
Before covering existing damp
Existing staining, condensation, leaks or damp supports need their cause investigated before the surface is closed. Moisture-resistant board does not repair a leak or remove condensation on its own. Plumbing, ventilation or building-envelope checks may be needed before dry construction starts, depending on what is found. Photographs help describe the situation but do not replace any necessary inspection.
How to prepare an assessment
Send overall photographs and close-ups of affected areas, stating whether the work is new construction or a repair. Explain where water reaches the surface, your intended finish and any previous problems. Where exposure exceeds that envisaged for H1, we consider other board families and specific systems. Feasibility and any required checks will be confirmed before the proposal is finalised.
- Room use and available ventilation.
- Direct water, splashing or ambient humidity.
- Finishes, pipework and previous damp problems.
Sources and technical documentation
Manufacturer references consulted on 14 October 2026. Selection and performance are confirmed against the current documentation for the system proposed for each project.