Overview
ISO 15148:2002 specifies a laboratory partial immersion test to determine the short‑term water absorption coefficient of building materials and products. The method quantifies capillary uptake (mass of water absorbed per unit face area per square root of time) and is intended to assess how materials behave when exposed to driving rain or surface wetting during storage and construction. It is not intended for materials used under sustained immersion or in saturated ground.
Keywords: ISO 15148:2002, water absorption coefficient, partial immersion, hygrothermal performance, capillary absorption.
Key topics and requirements
- Principle: Measure mass gain of a specimen whose bottom face contacts water; remove surface water by blotting before each weighing. Results express absorption per unit area per √time.
- Apparatus: Accurate balance (±0.1% of specimen mass), water tank with constant level control and point supports, and a timer.
- Specimens:
- Representative, regular shape and thickness (preferably full product thickness).
- Water contact area ≥ 50 cm² (preferably ≥ 100 cm²); for materials with large particles, dimensions must exceed particle size requirements.
- At least 3 specimens; if individual face area < 100 cm² then ≥ 6 specimens totaling ≥ 300 cm².
- Sides sealed with water- and vapour‑tight sealant to prevent edge flow; coatings/renders tested on normal substrate.
- Conditioning: Store specimens at test conditions until mass stabilizes within 0.1% over 24 h (see ISO 12570 for guidance).
- Test conditions: Mean temperature 18–28 °C and relative humidity 40–60% (permitted small variations, e.g. ±2 °C and ±0.05 RH). Water level maintained at (5 ± 2) mm above highest point of the base.
- Procedure and timing: Start timing at immersion; common weighing times include ~5 min, 20 min, 1 h, 2 h, 4 h, 8 h and at least 24 h. Blot and weigh quickly (preferably within 1 minute).
- Result expression: Water absorption coefficient defined as mass absorbed per face area per square root of time; units commonly expressed as kg/(m²·s^0.5) or alternatively as kg/(m²·h^0.5).
Applications and users
- Practical use: product development, quality control, conformity testing, specification of renders, coatings, insulation and other facade or substrate-mounted products vulnerable to rain uptake.
- Typical users: material manufacturers, independent test laboratories, building envelope engineers, architects, façade specialists, and compliance/regulatory authorities evaluating hygrothermal performance.
Related standards
- ISO 9346 - thermal insulation: mass transfer definitions (used for terms and units)
- ISO 12572 - vapour permeability / cup tests (complements liquid vs vapour transport characterization)
- ISO 12570 - conditioning of test specimens (for moisture conditioning procedures)
ISO 15148:2002 helps quantify capillary liquid transport into building materials, providing a standardized metric for comparing products and informing design and specification decisions related to moisture performance.