What are the typical physical properties of LWIC?
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?
No.
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 finished 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.
What is the minimum slope required of LWIC?
The minimum slope is 1/8 inch per foot to provide positive slope and to insure that water will drain. Consult local building codes.
What are the advantages of LWIC over rigid insulation board?
The advantages of LWIC include fire resistance, wind uplift, and seismic ratings, positive drainage, dimensional stability, moisture resistance, and re-roofable. LWIC is permanent, non-combustible, strong, economical, approved, and roofing compatible.
How thick is LWIC poured?
Both aggregate and cellular products are placed at a minimum thickness of 2 inches. One aggregate product can be placed at a thickness of 1 inch. LWIC systems (LWIC plus EPS Insulation) may be placed at a thickness greater than 18" depending on the specified slope (1/8 or inch per foot).
What precautions should be taken for top coat casting if snow is forecast?
If possible use heated mix water and/or High Early Strength cement (Type III) to accelerate the setting time before snow occurs.
What is involved in re-roofing over LWIC?
In many instances, it may be acceptable to cast LWIC directly over an existing membrane and insulation system. If the membrane is removed and there are base sheet nails of holes left on the deck, they shall be handled per specific job conditions. Unlike insulation board systems, just remove the existing membrane and install a new membrane per local requirements for acceptability. The LWIC system is permanent and does not need to be replaced.
Is it possible to cast over an existing LWIC roof (re-cover)?
Per structural engineer approval, cast new LWIC over existing LWIC and then apply the roofing membrane. Follow the procedure outlined in NRDCA Standard 500 for additional information.
How long does LWIC last?
If maintained in a watertight condition, LWIC should last for the life of the building.
How long is the warranty for LWIC?
One year from the date of substantial completion.
What regulatory approvals exist for LWIC?
All Products have FM (wind uplift) and UL (fire resistance) listings in addition to national and local code approvals.
Is LWIC a green product?
Yes. LWIC has appropriate credits for these requirements.