Is an ICF home quieter than a stick framed home?
Absolutely. The exterior walls are two layers of continuous insulation, the density of solid concrete and a layer of ½” gypsum board on the inside all contribute to superior sound suppression of STC 50 for the whole building envelope. Note: A wood frame system of equivalent STC rating would be 2 x 4 studs spaced 16˝ o/c, with 3½˝ absorptive material, 1 layer of 5 /8˝ Type X gypsum board on resilient channels spaced 16˝ o/c, and 2 layers of 5 /8˝ Type X gypsum board on the other side. (Courtesy of 1995 NBCC Section A9.10.3.1 Wall #W5a)
Can you vibrate or consolidate the concrete in ICFs?
Yes, consolidation of the concrete is one of the key elements in the placement of concrete in an ICF wall. Fox Blocks recommends internal vibration with a pencil vibrator, quickly in and slowly out.
Do ICFs require a special concrete mix design?
The concrete is normal strength, minimum 2500 psi (20 MPa) per building codes. The mix design specifies a smaller aggregate and higher slump than concrete typically used for floors. Most Ready-Mix suppliers are familiar with an ICF concrete mix design.
Why is the concrete limited to a placement height or lifts of 4 feet (1.2 m)?
To alleviate the pressure from the liquid concrete, the concrete is placed in layers or ‘lifts’. The first lift is limited to 4′ (1.2 m) of concrete around the perimeter of the building. This allows approximately one hour for the concrete to set-up before continuing with the next 4′ (1.2 m) lift. The lower lift provides support for the next lift as the concrete is placed continuously around the building in consecutive lifts to the top of the wall.
Is there a problem when placing concrete, dropping concrete from the top of the wall which may be over 8' (2.4 m)?
No. Specifications in the America Concrete Institute (ACI) do not limit the maximum distance concrete can free fall. Engineering studies and reports have shown that free fall from up to 35′ doesn’t reduce concrete quality and there is no evidence of segregation or weakened concrete strength. ICF concrete design calls for a high slump mix which assists in reducing segregation.
Can you build and pour concrete in cold weather?
Yes. The forms insulate the concrete and enhance the curing process. The top of the forms, or exposed concrete areas will need to be covered, temporarily, with insulation to prevent the exposed concrete from freezing. Fox Blocks projects can be constructed any time of the year, no delays for cold weather.
How do you control voids in the wall?
The concrete mix is a high slump 5″- 6.5″ (125 mm – 165 mm) with a smaller aggregate size so the concrete flows easily. The person in charge of placing the concrete should watch the concrete flow throughout the whole wall to ensure there are no void pockets. Internal vibrating provides good consolidation, eliminating voids.
What size and how much steel reinforcement is required in an ICF?
Fox Blocks walls are designed as reinforced concrete walls, with steel reinforcement bars specified to be installed vertically and horizontally, as the walls are built. Typical reinforcement bar sizes used are #4 or #5 (10 m or 15 m).
3-Story ICF Construction for Homes