Belzona 3211 (Lagseal) is a single-component, waterbased, microporous coating for the sealing and long term protection of all types of thermal insulation. 

It can be applied by spray or brush without the need for specialist tools. It is a two layer application reinforced with glass fiber sheeting.

This versatile system is suitable for applications onto new and existing lagging on steam, condensate or chilled pipelines. It is also resistant to water, weather and fire.



A water-based acrylic emulsion membrane incorporating a polymer bonded glass reinforcing sheet (Belzona 9321) designed to provide seamless, flexible protection to all types of thermal insulation and cladding systems.Belzona 3211 (Lagseal) is water, weather and fire resistant, and conforms to the requirements for a ‘Class O’ surface for ‘The UK Building Regulations 1991’ and ‘Class A’ in accordance with ‘ASTM E84’. The system provides protection from water ingress whilst its microporous nature allows trapped moisture from within the insulation to evaporate. This solvent-free, single pack system requires no mixing and is simple to apply to damp as well as dry insulation.

Key benefits:

  • Fire resistant
  • Easily applied by brush with no mixing required
  • Reduced health and safety risks as it is solvent-free
  • Application and cure at cold temperature – no hot work involved
  • Will not support growth of bacteria or algae  providing a hygienic finish
  • Excellent oil resistance
  • Withstands movement due to temperature fluctuations and vibrations within the system
  • Resistant to water, steam impingement, infra-red and ultra-violet radiation
  • Excellent adhesion to a wide range of materials including calcium silicate, glass fibre, mineral wool, foam, steel and stainless steel.

Applications for Belzona 3211 (Lagseal) include:

  • Protection of insulation on pipes, air-conditioning ducting, valve boxes, flange covers, boilers, pressure vessels, bulk storage tanks and heat exchangers
  • Long-term lagging protection on new and existing steam, condensate or chilled pipelines
  • Seamless encapsulation of elbows, T pieces flanges and complex contours
  • Tank base sealing


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