What fasteners are recommended for ICFs?
Fox Blocks has conducted numerous fastener tests for pull-out strength and shear capacity for various fasteners – screws, ring shank nails and staples into the plastic webs. The recommendation for interior and exterior applications of finish materials is for the use of screws which provide the best holding capacity into the plastic webs or fastening strips in the forms which are identified on each block.
The EPS insulation does not provide any holding capacity for fasteners.
When can I backfill the foundation wall?
The concrete must cure for a minimum of 7 days and the foundation wall must be laterally supported, meaning the floor system is installed supporting the top of the wall. All below grade waterproofing / dampproofing must be installed.
Can I install a 16' garage door and / or large openings in a concrete wall?
Yes, if the following criteria is available for the design of a concrete lintel (beam) over the opening – concrete lintel depth minimum 16″ (400 mm) or more with no point loads. Larger openings would require an engineered design.
Does the EPS provide support for a wood sill plate?
No, the EPS has no structural capacity to support any loads. Wood sill plates must achieve the required bearing from the concrete within the ICF. A wood plate that cantilevers 1⁄3 over the EPS and bears 2⁄3 on the concrete is allowable. This can be done with a minimum 2 x 6 plate. If a 2 x 4 plate is required, a taper top form should be used to extend the concrete under the plate.
How do frame in openings?
Fox Blocks has developed the Fox Buck specifically to frame openings such as windows and doors. The Fox Buck provides insulation around the opening plus support for the attachment of the window or door.
Is an ICF house faster to build?
The assembly and placement of concrete may take the same time as to build with conventional methods. The advantage with Fox Blocks is that the walls are now insulated, have a vapor and air barrier installed and are ready for finishes once the windows and roof are installed. These benefits will save weeks and/or months depending on the size of the projects.
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.