Lightweight Insulating Concrete


Specification Details

8.5" x 11"
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Lightweight Insulating Concrete

Use this 3 part specification template to specify a poured-in-place lightweight insulating concrete roof deck, with or without integral rigid insulation.

Lightweight Insulating Concrete (LWIC) is a versatile building material used primarily for roof insulation and as a structural roof decking system. It consists of a mixture of Portland cement, water, and lightweight aggregates, such as expanded polystyrene or perlite. Here are some key characteristics and benefits:

Key Characteristics

  • Lightweight: As its name suggests, LWIC is significantly lighter than traditional concrete, reducing the load on structures and making it an ideal choice for roofing applications.
  • Insulating Properties: LWIC provides excellent thermal insulation, helping to maintain consistent indoor temperatures and reduce energy costs.
  • Compressive Strength: While lighter than standard concrete, LWIC still offers good compressive strength, supporting foot traffic and equipment on roofs.
  • Versatility: It can be molded to various shapes and slopes on roofs, facilitating effective water drainage.


  • Energy Efficiency: The insulating properties of LWIC contribute to energy savings by enhancing a building’s thermal performance.
  • Durability: LWIC roofs can last a long time, providing a durable, protective layer that withstands weather and environmental conditions.
  • Sound Insulation: In addition to thermal insulation, LWIC also offers sound dampening benefits, reducing noise transmission.
  • Fire Resistance: Like traditional concrete, LWIC is fire-resistant, adding an extra layer of safety to buildings.


  • Roof Insulation: Used as a roof insulation material, particularly in commercial and industrial buildings.
  • Roof Decks: It serves as a lightweight option for creating sloped roof decks that facilitate drainage.
  • Floor Insulation: Though less common, LWIC can also be used for insulating floors, especially in scenarios where lightweight solutions are preferred.

LWIC is a practical choice for projects requiring a balance between insulation, structural integrity, and lightweight characteristics. Its adaptability and performance make it a preferred material for modern construction projects seeking energy efficiency and sustainability.


Specification Notes:

  • Material is used for roof decks only; it cannot be used for structural members or on surfaces subject to pedestrian or vehicular traffic.
  • Lightweight insulating concrete roof decks provide insulation and can be sloped for drainage. These decks can be rated for wind uplift and are classified as noncombustible. They must be installed over a permanent roof deck such as galvanized metal decking or concrete. Since moisture can be trapped in the material as it is mixed and placed, many membrane roofing system manufacturers require the use of vents to allow moisture to escape and prevent blistering of the roof membrane.


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