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Lightweight Insulating Concrete Information

Lightweight Insulating Concrete Roof Systems, (LICRS)

The lightweight insulating concrete roof installation system have a long and proud history of over 60 years that began in the northern United States. At that time, building codes requiring fire resistant thermal barrier provided by lightweight insulating concrete roof decks helped to meet this new need. Today there are hundred of thousands of successful lightweight insulating concrete decks installed in North America and around the world.


Lightweight insulating concrete roof systems offer the unique opportunity to remove water from the roof. The ability to design custom slope to drain conditions and then have the plan followed in the roof construction sets these systems apart from rigid insulation systems. However to take advantage of this opportunity requires a large number of designs that are very difficult to create by hand drawing methods.

Design parameters for the roof slope layout

A proprietary computer program has been developed that allows the following roof top conditions to vary to produce the optimum design. The program considers the following variables for each design.

    • Type of substrate ( re-roof, structural concrete, metal deck)
    • Type of insulating concrete ( aggregate or cellular)
    • Minimum thickness of concrete above polystyrene
    • R-value (minimum or average)
    • Thickness of slurry coat
    • Distance between polystyrene steps
    • Maximum height of polystyrene step
    • Pre-defined design slope
    • Slope limited by wall height
    • Combination of pre-defined slope and wall height limitations in same drainage area
    • One drain or multiple drains in same drainage area
    • Height of drains above substrate surface
    • Distance drain is located from high or low point of drainage area
    • Cricket design to move water between multiple drains
    • Once an ICRDS (Insulated Concrete Roof Deck System) is installed, building owners will never have to replace their roof insulation again and building occupants will enjoy the comforts of the construction industry`s most progressive roof underlayment system.


    • The ICRDS is more economical than installing tapered, rigid board systems or sloping the structural concrete.
    • Provides excellent slope-to-drain over flat or irregular substrates.
    • May be roofed in 48-72 hours. The base sheet fastener should attain a minimum 40-pound withdrawal value.
    • High moisture resistance and compressive strength.
    • Dimensional stability and the ability to mechanically fasten the roofing membrane to the insulation.
    • Excellent wind and fire resistance properties.
    • Eliminates low spots on existing roof decks.
    • Achieves long-term insulating value.
    • Depending on the condition of the existing roof system, the ICRDS can also eliminate the need for costly tear-off due to industry restrictions and simplify surface preparation.


Can be installed over non-slotted or slotted galvanized corrugated metal decks, structural concrete substrates and, where appropriate, over existing roofs in recover applications. It is not intended for use in extremely hot, dry climates. ICRDS excellent fire resistance properties make it cost effective versus the more expensive alternative of adding a fireproof coating to the deck`s underside, as required by most systems incorporating conventional rigid insulation board. The lightweight concrete is placed at a minimum 2-inch thickness over the top of the EPS (expanded polystyrene foam).

How much does ICRDS cost?

Cost-effective lightweight Insulating Concrete Systems varies in price by geographical area and by application requirements. Your LCS sales representative will be glad to assist you with budget numbers and binding quotations for our products and services.

How do you increase the R-value of LWIC?

The R-value of any LWIC is increased by adding expanded polystyrene insulation board during application of the LWIC. A LWIC system (LWIC plus EPS insulation) can easily achieve 50 R`s for the installation.

What is the equilibrium moisture content of cellular concrete?

The equilibrium moisture content of cellular concrete is typically 14%-18% by weight.

When can LWIC be roofed?

Roofing may begin 2-4 days after placement. The base sheet fastener should attain a minimum 40-pound withdrawal value.

How resistant to weather is LWIC?

After a LWIC deck is roofed, it is highly resistant to weather conditions as has been demonstrated for over 60 years of continuous applications in all geographic areas of theUnited States and in other parts of the world.

If EPS is in place and a threat of rain exists, what is the best procedure to follow?

Place the slurry coat so that the bond holes are full of material. It is not necessary to slurry coat the board surfaces. A slurry coat on the board is acceptable for next day topping without any special treatment such as a bonding agent.

What types of roof membranes can be installed over LWIC?

Built-up Roofing, Modified Bitumen, and Single Ply Membranes of various approved compositions have been successfully installed over LWIC.

How far can cellular concrete be pumped?

Cellular concrete is a very easily pumped, highly fluid mixture. The bulk of cellular concrete is placed by pumping. Cellular concrete typically will move through the pump lines using less pressure than typical heavier grout mixes. Documentation of cellular concrete being pumped up to and exceeding 500 ft. vertically and 10,000 feet horizontally is commonly available. This is also dependent on the contractor`s equipment capability.

Are control joints needed for thermal movement in a LWIC system?


What is an acceptable finish for LWIC?

A surface finish free of ridges and protrusions is an acceptable finish for roofing application. Most LWIC is left to self-seek a level and not surface &%3B finished &%3B in the traditional sense. Much cellular concrete is covered by another material. A floor overlayment type smoother tool can be used simply to break the surface air cells and create a more uniform and polished look to the surface in the rare case when a more uniform surface appearance is desired.