Moisture resistance: H1, H2 and H3
What's the difference between H1 and H2 plasterboard?
EN 520 Type H boards (H1–H3, H1 = lowest water absorption) have water-repellent core additives for intermittent moisture — kitchens, bathrooms, sheltered soffits. For tiled areas with repeated, persistent wetting, manufacturers still recommend a tanking system.
The H classes rank how little water a board’s core will take up. They are a real, measurable property — but “moisture resistant” is a narrower promise than it sounds, and reading it as “waterproof” is how moisture boards end up failing in the wrong place.
What the H number means
EN 520 Type H boards have water-repellent additives worked into the gypsum core, and are graded by surface water absorption into three classes.
- H1 — the lowest water absorption, and so the strongest moisture claim.
- H2 — an intermediate class, above H1’s absorption limit.
- H3 — the highest permitted absorption of the three.
The counter-intuitive part is that a lower number is the better board: H1 absorbs less water than H2. So when a specification asks for H2, an H1 board meets and exceeds it — an equal-or-better direction — whereas offering H2 against an H1 spec would be a downgrade.
What moisture resistance is — and isn’t — for
Type H boards are made for intermittent moisture and humidity: kitchens, bathrooms, utility rooms and sheltered soffits, where the board is exposed to damp air and occasional splashing but not continuous wetting.
They are not a tanking membrane. For tiled areas subject to repeated, persistent water — a shower enclosure, a wet room — manufacturers still recommend a proper tanking or waterproofing system behind the finish. Moisture resistance buys tolerance, not immersion.
H classes, glass-mat boards and substitution
Paper-faced Type H boards are not the only wet-area option: glass-mat boards (marked to EN 15283-1, e.g. GM-H1) tackle the same job with a different construction and their own markings. And moisture resistance is a separate property from vapour control — a foil-backed board manages diffusion, not liquid water.
For a defensible substitution, drywallDB matches the moisture class or betters it, never offering a weaker one as equivalent, and keeps the glass-mat and vapour-control families distinct rather than treating them as interchangeable upgrades.
Frequently asked questions
- Is H1 better than H2?
- Yes. The number ranks water absorption, and a lower number means less absorption — so H1 is the stronger moisture claim. An H1 board meets a spec that asks for H2; the reverse is a downgrade.
- Can I use moisture-resistant board in a shower?
- Not on its own. Type H boards suit intermittent damp and splashing, but a shower or wet room needs a tanking or waterproofing system behind the tiles. Moisture resistance is tolerance, not waterproofing.
- Is a moisture-resistant board the same as a vapour-control board?
- No. Moisture resistance (Type H) is about the core resisting liquid water absorption; vapour control (a foil backing, to EN 14190) is about slowing water-vapour diffusion through the wall. Different jobs, different standards.
Related guides
- Vapour-control (foil-backed) boards — What does a foil backing on plasterboard actually do?
- EN 520 board types explained — What do EN 520 Type A, D, E, F, H, I, P and R mean?
- Tapered edge vs square edge — TE or SE — which edge profile do I need?