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Creating Bare ICF Concrete Walls for Stairwells, Elevator Shafts, Warehouses

BuildBlock Hardwall showing webs, cement board, and MDF or plywood.

BuildBlock’s Hardwall is used for creating Bare ICF Concrete Walls for Stairwells, Elevator Shafts, Warehouses.

In commercial applications such as elevator shafts, warehouses, and stairwells a bare concrete wall may be required to meet fire codes. This can easily be accomplished using an ICF wall system and maintain insulation value. Even more insulation value can be retained by integrating the BuildBlock ThermalSert insulation insert into the wall.

BuildBlock Knockdown ICF forms have multiple uses aside from the traditional ICF form. They have been used to build footing forms, pilasters and other custom structural and architectural pieces. One innovative way to use these forms, and save labor at the same time is to attach sheathing (either cement fiber board, plywood, OSB or another sheet material to the web inserts without the foam panel molded onto them.

This makes a 2 inch thicker wall, (with a ready to finish face when using cement fiber boards) and eliminates the need to strip foam and webs from inside stairwells, elevator shafts, or in warehousing, where the durability of a solid concrete wall as the finish surface is more desirable provide the benefits of ICF exterior insulation.

To install this system, simply rip your sheathing material into 16” strips, assemble the plywood to the web inserts with the alignment jig, using 1-1/4” – 1-5/8” coarse thread #10 Pan Head Screws. Then assemble the rest of the block by adding web bridges and a BuildLock Panel. Stack the forms as usual, aligning the outside faces. It is recommended to attach 1×4 strapping on the plywood side of the forms to ensure a smooth finish. The 1x4s should bridge the vertical or horizontal seams, to maintain a smooth finish, and prevent the plywood from warping along seams.

Once the walls are stacked, and poured, the plywood or OSB can be easily removed from the webs, and a smooth concrete wall is ready for stucco, or other finishes. Leave the cement fiber product in place as a smooth finish to build up plaster or other surface finishes. It will bond tightly to the concrete and be reinforced with the screws attaching it to the webs.

BuildBlock Hardwall is best assembled using the jig depicted above.  This tool ensures proper alignment of the webs when attaching the plywood face.  The dimensions given ensure minimum clearances for the webs during assembly, and allow for quick assembly without constant realignments.  The jig should be built from dimensionally stable lumber and all parts should be checked for defects and bows prior to assembly.  We recommend using LVL material for spacers, but 2X lumber may also be used, although, depending on the final assembled height of the jig, additional spacing material may be required, due to the variation in plywood and lumber thicknesses. There are 2 plywood layers and their orientation is critical for this jig.  The larger gap parts must be on top as they allow the web inserts to slip into these gaps, and ensure that the webs are square to the plywood face.  The smaller gaps ensure that the webs sit at the correct depth in relation to the plywood.

When stacking BuildBlock Hardwall, it is important to maintain the alignment of the plywood faces, as this will affect the final finish of the wall. This is best accomplished by strapping along or across seams, which will prevent them from buckling from water absorption. The use of CD-X or treated plywood can assist with this as well.

Cutting the plywood accurately, taking care to ensure it is both square and correctly sized, is critical to a high quality install. All ICF forms will settle with the weight of the concrete. The plywood portion of the walls will be less subject to this settling. Out of square or mis sized plywood can exacerbate this condition leading to, uneven or out of plumb walls.

Finishing the walls after the concrete has cured begins with removal of the plywood. The screws shouldn’t be difficult to remove, as they will be embedded primarily in the polypropylene web inserts. The web inserts will be visible on the wall, and depending on the desired finish, may need to be prepped to accept the finish. The walls cam be painted, have stucco or plaster applied, or can be left a concrete grey with a clear penetrating sealer applied. If the walls are to be located to the outside, it is recommended to provide a suitable finish to cover the web inserts, as they will need to be protected from UV exposure.

Attachment to the wall will be the same as with any standard poured concrete wall, and can use tapcon fasteners, or other anchoring systems. The plastic web inserts do offer an attachment point as well. The depth may be limited if not using a concrete screw.

More Information at the BuildBlock Hard Wall Product Page

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